A transistor power amplifier is provided with direct-current-coupling between stages and to the loudspeaker. The output stage is push-pull single-ended and includes two transistors connected in series at a midpoint of the stage. A split power supply has a center-tap connected to one output terminal and the other output terminal is connected to said output stage midpoint. Amplification and drive stages are direct-current-coupled in cascade to the output stage. A direct-current negative feedback network extends from the output stage to an amplification stage to maintain the output terminals at substantially the same quiescent potential to prevent direct-current flow through the voice-coil of the loudspeaker.
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76. A transistor power amplifier for high fidelity music reproduction without audible distortion or listening fatigue under extended critical listening conditions and comprising
a single-ended push-pull output stage including at least two transistors connected in series at a midpoint of the stage, a split power supply connected to said output stage and having a center-tap, a pair of output terminals, means D.C.-coupling one of said output terminals to said center-tap, means D.C.-coupling the other output terminal to said output stage midpoint, a complementary-symmetry push-pull drive stage, means D.C.-coupling said drive stage to said output stage, amplification means, means D.C.-coupling said amplification means to said drive stage, a D.C. feedback network extending from said output stage to said amplification means for maintaining said output terminals at substantially the same D.C. potential, said amplification means comprising two common-emitter stages direct-current-coupled in cascade, a first of said common-emitter stages including at least one transistor of a predetermined polarity type and connected in the common-emitter phase-reversing mode and having a base, a collector and an emitter, the second of said common-emitter stages including a transistor of the opposite polarity type and connected in the common-emitter phase-reversing mode and having a base direct-current-coupled to said first common-emitter stage transistor collector and having a collector direct-current-coupled to said drive stage, said first common-emitter stage having a base bias network for maintaining said transistor base thereof at a relatively fixed direct-current quiescent potential, said base bias network comprising a resistor extending from said transistor base to ground, said first common-emitter stage having a feedback injection node direct-current-coupled to said emitter to apply a feedback signal effectively in series with the input signal so as to raise the input impedance of said first common-emitter stage in response to the injection of a negative feedback signal into said node, said D.C. feedback network being direct-current-coupled to said feedback
injection node. 91. A transistor power amplifier for high-fidelity music reproduction without audible distortion or listening fatigue under extended critical listening conditions and comprising
a first amplifier stage including an input circuit and an output circuit, an output stage having a first output terminal for direct-coupling to one terminal of a loudspeaker or other load, a power supply connected to said output stage, a second output terminal for direct-current-coupling to the other terminal of said load, first circuit means direct-current-coupling said first amplifier stage output circuit to said output stage to drive the latter, a substantially fixed source of reference potential of a magnitude substantially independent of variations in the potential of said power supply, second circuit means connected to said reference potential source and said first amplifier stage input circuit to supply bias current thereto at a relatively fixed quiescent potential so as to adjust the quiescent potential of said first output terminal to that of said second output terminal, a node having a direct-current potential varying substantially proportionately to that of said first output terminal, and a passive feedback impedance direct-current-coupled between said node and said first amplifier stage, thereby providing a direct-current negative feedback loop to reduce any tendency of the quiescent potential of said first output terminal to vary from that of said second output terminal, said first amplifier stage comprising a differential pair of transistors including a first transistor and a second transistor, said first transistor being connected in the common-emitter node and having a collector forming part of said first amplifier stage output circuit whereby the signal at said collector is transmitted to said output stage, said first transistor having a base forming part of said first amplifier stage input circuit, a ground constituting said reference potential source, said second circuit means including a resistor connected between said ground and said first transistor base, said first and second transistors having mutually connected emitters, said second transistor having a base, said passive feedback impedance being direct-current-coupled to said second transistor base, said output stage including at least a pair of output transistors connected in a push-pull arrangement and each having a base, said first circuit means including a push-pull drive stage having at least two complementary transistors each direct-current-coupled to a respective one of said output transistor bases, said drive and output stages being connected to operate in the
emitter-follower mode. 93. A transistor power amplifier for high-fidelity music reproduction without audible distortion or listening fatigue under vigorously critical extended listening conditions and comprising
a single-ended push-pull output stage having a first output terminal for direct-current-coupling said stage to one end of a loudspeaker or other load, a power supply connected to said output stage, a second output terminal for direct-current-coupling the other end of said load to said power supply, a preceding amplifying stage comprising a transistor having a base electrode and an emitter electrode, an active network direct-current-coupling said preceding stage to said output stage, a bias network maintaining one of said electrodes at a relatively fixed direct-current quiescent potential independent of variations in the load current or in the power supply potential, and a negative feedback network responsive to the potential of said first output terminal and direct-current-coupled to the other electrode for applying thereto a potential proportional to the direct-current quiescent potential of said first output terminal to maintain said quiescent potential substantially equal to that of said second output terminal, and wherein said preceding amplifying stage transistor is of a predetermined polarity type and connected in the common-emitter mode so as to constitute a first common-emitter transistor, said active network including a second common-emitter stage having only a single amplifying transistor of a polarity type opposite to that of said first common-emitter transistor and having an emitter and a collector output network, a push-pull drive stage including a pair of complementary transistors each having a base, an emitter and a collector, said second common-emitter transistor collector output network being direct-current-coupled to said bases of the drive stage transistors, said power supply having positive and negative terminals, conductive means connecting said emitter of said second common-emitter stage transistor to one of said supply terminals to maintain the potential of said emitter at approximately the potential of said supply terminal, means connecting said drive stage transistor collectors to said power supply terminals respectively, means direct-current-coupling said drive stage to said output stage, means connecting said drive stage transistor emitters to the output terminal whereby said drive and output stages operate in the emitter-follower mode, said negative feedback network transmitting a feedback signal to said emitter electrode of said preceding amplifying stage transistor, said bias network including a resistor having one end connected to said base electrode and its other end connected to ground, said feedback network including a feedback resistor for transmitting a feedback signal in the back direction toward said last-recited emitter electrode, and conductive means separate from said feedback resistor and connected to said emitter electrode for conducting at least a substantial portion of the emitter current of said first common-emitter preceding amplifying stage
transistor. 75. A transistor power amplifier for high-fidelity music reproduction without audible distortion or listening fatigue under extended critical listening conditions and comprising
a single-ended push-pull output stage having a first output terminal for direct-current coupling said stage to one end of a loudspeaker or other load, a power supply connected to said output stage, a second output terminal for direct-current coupling the other end of said load to said power supply, a preceding amplifying stage comprising a transistor having a base electrode and an emitter electrode, an active network direct-current coupling said preceding stage to said output stage, a bias network maintaining one of said electrodes at a relatively fixed direct-current quiescent potential independent of variations in the load current or in the power supply potential, and a negative feedback network responsive to the potential of said first output terminal and direct-current coupled to the other electrode for applying thereto a potential proportional to the direct-current quiescent potential of said first output terminal to maintain said quiescent potential substantially equal to that of said second output terminal, and wherein said preceding amplifying stage transistor is connected in the common-emitter mode, said active network including a push-pull drive stage comprising a pair of complementary drive transistors each having an emitter, and means connecting said emitters to said output terminal whereby said drive and output stages together effectively operate in the emitter-follower mode, and wherein said output stage comprises a pair of output transistors of the same polarity type and each having a base and an emitter, one of said drive transistors having an emitter direct-current coupled to the base of a respective one of said output transistors, the other of said drive transistors having a collector direct-current coupled to the base of the other output transistor, the emitter of said one output transistor being connected to said first output terminal, said power supply having an ungrounded supply terminal, and conductive means connecting the emitter of said other output transistor to said ungrounded power supply terminal, and wherein said preceding common-emitter amplifying stage transistor has a collector and an emitter and is of a predetermined polarity type, a second common-emitter amplifying stage including a transistor of a polarity type opposite to that of said preceding amplifying stage transistor and having a base and a collector, said first common-emitter transistor collector being direct-current-coupled to said second common-emitter transistor base, said second common-emitter transistor collector being direct-current-coupled to said drive stage, said bias network maintaining said base electrode of said first common-emitter preceding amplifying stage transistor at said relatively fixed direct-current quiescent potential and including a resistor extending from said base electrode to ground, said negative feedback network being direct-current-coupled to said emitter electrode of the first common-emitter preceding amplifying stage transistor, said feedback network including a feedback resistor for transmitting a feedback signal in the back direction toward said last-recited emitter electrode, and conductive means separate from said feedback resistor and connected to said emitter electrode for conducting at least a substantial portion of the emitter current of said first common-emitter preceding amplifying stage
transistor. 100. A transistor power amplifier for high-fidelity music reproduction without audible distortion or listening fatigue under extended critical listening conditions and comprising
a single-ended push-pull output stage having a first output terminal for direct-current-coupling said stage to one end of a loudspeaker or other load, a power supply connected to said output stage, a second output terminal for direct-current coupling the other end of said load to said power supply, a preceding amplifying stage comprising a transistor having a base electrode and an emitter electrode, an active network direct-current-coupling said preceding stage to said output stage, a bias network maintaining one of said electrodes at a relatively fixed direct-current quiescent potential independent of variations in the load current or in the power supply potential, and a negative feedback network responsive to the potential of said first output terminal and direct-current-coupled to the other electrode for applying thereto a potential proportional to the direct-current quiescent potential of said first output terminal to maintain said quiescent potential substantially equal to that of said second output terminal, and wherein said preceding amplifying stage transistor is connected in the common-emitter mode, said active network including a push-pull drive stage comprising a pair of complementary drive transistors each having an emitter and a base, means connecting said emitters to said output terminal whereby said drive and output stages together effectively operate in the emitter-follower mode, said preceding common-emitter amplifying stage transistor having a collector and an emitter and being of a predetermined polarity type, a second common-emitter amplifying stage including a transistor of a polarity type opposite to that of said preceding amplifying stage transistor and having a base and a collector, said preceding common-emitter transistor collector being direct-current-coupled to said second common-emitter transistor base, network means direct-current-coupling said second common-emitter transistor collector to said drive stage transistor bases, said bias network maintaining said base electrode of said first common-emitter preceding amplifying stage transistor at said relatively fixed direct-current quiescent potential and including a resistor extending from said base electrode to ground, said negative feedback network transmitting a direct-current feedback signal to said emitter electrode of the first common-emitter preceding amplifying stage transistor, said feedback network comprising a first resistor, a second resistor and a capacitor, said first resistor having one end direct-current-coupled to said output stage midpoint, said second resistor having one end connected to the other end of said first resistor and its other end connected to one end of said capacitor, the other end of said capacitor being connected to ground, said output stage comprising a pair of output transistors of the same polarity type and each having a base and an emitter, one of said drive transistors having an emitter direct-current-coupled to the base of a respective one of said output transistors, the other of said drive transistors having a collector direct-current-coupled to the base of the other output transistor, conductive means connecting the emitter of said one output transistor to said first output terminal, said power supply having a supply terminal ungrounded with respect to D.C., conductive means connecting the emitter of said other output transistor to said ungrounded power supply terminal. 1. A transistor power amplifier comprising a single-ended push-pull output stage including at least two transistors connected in series at a midpoint of the stage, a split power connected to said output stage and having a center-tap, a pair of output terminals, means D.C.-coupling one of said output terminals to said center-tap, means D.C.-coupling the other output terminal to said output stage midpoint, a complementary-symmetry push-pull drive stage, means D.C.-coupling said drive stage to said output stage, amplification means, means D.C.-coupling said amplification means to said drive stage, and a D.C. feedback network extending from said output stage to said amplication means for maintaining said output terminals at substantially the same D.C. potential.
2. An amplifier as recited in
3. An amplifier as recited in
4. An amplifier as recited in
5. In combination, a pair of amplifiers each as recited in
6. A transistor power amplifier as recited in
transistor base. 7. In combination, an amplifier as recited in claim 1, A transistor power amplifier comprising a single-ended push-pull output stage including at least two transistors connected in series at a midpoint of the stage, a split power supply connected to said output stage and having a center-tap, a pair of output terminals, means D.C.-coupling one of said output terminals to said center-tap, means D.C.-coupling the other output terminal to said output stage midpoint, a complementary-symmetry push-pull drive stage, means D.C.-coupling said drive stage to said output stage, amplification means, means D.C.-coupling said amplification means to said drive stage, and a D.C. feedback network extending from said output stage to said amplification means for maintaining said output terminals at substantially the same D.C. potential, preamplifier means connected in cascade with said amplifier, an inner negative feedback loop including said amplifier for raising the high-frequency cutoff of said amplifier to a predetermined frequency, said preamplifier means comprising a transistor stage preceding said inner feedback loop, said transistor stage having a high-frequency cutoff substantially lower than said predetermined frequency, and an outer negative feedback loop including said amplifier and said preamplifier transistor stage. 8. A transistor power amplifier as recited in
9. In combination, an amplifier as recited in
10. In combination, a pair of amplifiers each as recited in
11. A transistor power amplifier as recited in
12. A transistor power amplifier as recited in
13. A transistor power amplifier as recited in
14. A transistor power amplifier as recited in
15. A transistor power amplifier as recited in
16. A transistor power amplifier as recited in
17. A transistor power amplifier as recited in
18. A transistor power amplifier as recited in
19. A transistor power amplifier as recited in
to said drive stage transistor bases. 20. A transistor power amplifier as recited in claim 1 for reproduction without audible distortion by said amplifier of a high-fidelity music signal and comprising a single-ended push-pull output stage including at least two transistors connected in series at a midpoint of the stage, a split power supply connected to said output stage and having a center-tap, a pair of output terminals, means D.C.-coupling one of said output terminals to said center-tap, means D.C.-coupling the other output terminal to said output stage midpoint, a complementary-symmetry push-pull drive stage, means D.C.-coupling said drive stage to said output stage, amplification means, means D.C.-coupling said amplification means to said drive stage, and a D.C. feedback network extending from said output stage to said amplification means for maintaining said output terminals at substantially the same D.C. potential, and wherein said amplification means comprises at least a first transistor of one polarity type and a second transistor of complementary type and each transistor having a collector, a base and an emitter, network means constituting a D.C. signal transmission path from the first transistor collector to the second transistor base, a ground, bias means maintaining said first transistor base at a quiescent D.C. potential relatively fixed with respect to said ground, means A.C.-coupling said second transistor emitter to said ground, said feedback network transmitting a feedback signal to vary the potential at said first transistor emitter, said feedback network being connected to said first transistor emitter, and means for transmitting an input signal to said first transistor base. 21. A transistor power amplifier as recited in
22. A transistor power amplifier as recited in
23. A transistor power amplifier as recited in
24. A transistor power amplifier as recited in
25. A transistor power amplifier as recited in
26. A transistor power amplifier as recited in
27. A transistor power amplifier as recited in
28. A transistor power amplifier as recited in
29. A transistor power amplifier as recited in
30. A transistor power amplifier comprising a first stage including a transistor having a base electrode, an emitter electrode and a collector, means transmitting an input signal to said base electrode, a ground, a potential source maintained at a substantially fixed predetermined voltage with respect to said ground independent of variations in power supplied to or drawn from said amplifier, means connecting one of said electrodes to said potential source, an output stage, circuit means providing a D.C. signal transmission path from said collector to said output stage, an output terminal adapted to be connected to a loudspeaker or other load, a passive direct-current feedback network extending from said output stage to one of said electrodes, and means D.C.-coupling said output stage to said output terminal.
31. A transistor power amplifier as recited in
32. A transistor power amplifier as recited in
33. A transistor power amplifier as recited in
34. A transistor power amplifier as recited in
coupled to said emitter electrode. 35. A transistor power amplifier as recited in claim 30 and comprising a first stage including a transistor having a base electrode, an emitter electrode and a collector, means transmitting an input signal to said base electrode, a ground, a potential source maintained at a substantially fixed predetermined voltage with respect to said ground independent of variations in power supplied to or drawn from said amplifier, means connecting one of said electrodes to said potential source, an output stage, circuit means providing a D.C. signal transmission path from said collector to said output stage, an output terminal adapted to be connected to a loudspeaker or other load, a passive direct-current feedback network extending from said output stage to one of said electrodes, and means D.C.-coupling said output stage to said output terminal, a second stage including a transistor of a polarity type complementary to that of said first stage having a collector, a base and an emitter, a network D.C.-coupling the first stage transistor collector to the second stage transistor base, said potential source being connected to said first stage transistor base to supply bias current to the latter, means A.C.-coupling said second stage transistor emitter to said ground, said feedback network transmitting a feedback signal to vary the potential at said first transistor emitter, a drive stage comprising at least two complementary transistors each having an emitter and a base, network means constituting D.C. transmission paths from said second stage transistor collector to said drive stage transistor bases, and means connecting said drive stage transistor emitters to said output terminal. 36. A transistor power amplifier as recited in claim 35 and comprising a third transistor having a collector, a base and an emitter, means connecting said third transistor emitter to said first stage transistor emitter, common impedance means having one end connected to said connected emitters, means A.C.-coupling the other end of said impedance means to said ground whereby said first stage transistor and said third transistor coact in the differential amplifier mode, said feedback network having a passive component including an impedance extending from said output stage to said third transistor base and said feedback network further having an active component including said third transistor to transmit said feedback signal to said first stage transistor emitter, means D.C.-coupling said power supply center-tap to said ground, said bias reference node being at D.C. ground potential, a second output stage, and network means for selectably connecting said second output stage either in parallel or in series with said first output stage. 37. A transistor power amplifier as recited in
38. A power amplifier comprising a first amplifier stage including an input circuit and an output circuit, an output stage having a first output terminal for direct-current coupling to one terminal of a loudspeaker or other load, a power supply connected to said output stage, a second output terminal for direct-current coupling to the other terminal of said load, first circuit means direct-current coupling said first amplifier stage output circuit to said output stage to drive the latter, a substantially fixed source of reference potential of a magnitude substantially independent of variations in the potential of said power supply, second circuit means connected to said reference potential source and said first amplifier stage input circuit to supply bias current thereto at a relatively fixed quiescent potential so as to adjust the quiescent potential of said first output terminal to that of said second output terminal, a node having a direct-current potential varying substantially proportionately to that of said first output terminal, and a passive feedback impedance direct-current coupled between said node and said first amplifier stage, thereby providing a direct-current negative feedback loop to reduce any tendency of the quiescent potential of said first output terminal to vary from that of said second output terminal.
39. A power amplifier as recited in
40. A power amplifier as recited in
41. A power amplifier as recited in
42. A transistor power amplifier comprising a split power supply having a center-tap and two supply terminals of opposite polarity, a single-ended push-pull output stage including a pair of transistors connected in series at a junction and each having one electrode connected to a respective one of said supply terminals and another electrode, a first output terminal for connection to one end of a speaker or other load, first circuit means connecting said other electrodes of said output transistors to said first output terminal, a second output terminal for connection to the other end of said load, means coupling said second output terminal to said supply center-tap, a voltage-amplification stage including a transistor having a direct-current feedback signal injection node and a collector, a direct-current feedback network for injecting into said node a feedback signal proportional to the direct-current potential of said junction, second circuit means direct-current coupling said voltage-amplification transistor collector to said output stage, said voltage-amplification transistor having a base electrode and an emitter electrode, a bias supply node having a relatively fixed voltage, a bias impedance extending from said bias supply node to one of said voltage-amplification transistor electrodes to supply bias current to said one electrode and to maintain the latter at an approximately constant direct-current potential, said other voltage-amplification transistor electrode constituting said feedback injection node and having said feedback network direct-current coupled thereto.
43. A transistor power amplifier as recited in
44. A transistor power amplifier as recited in
voltage-amplification transistor and said output stage. 45. A transistor power amplifier as recited in claim 44 comprising a split power supply having a center-tap and two supply terminals of opposite polarity, a single-ended push-pull output stage including a pair of transistors connected in series at a junction and each having one electrode connected to a respective one of said supply terminals and another electrode, a first output terminal for connection to one end of a speaker or other load, first circuit means connecting said other electrodes of said output transitors to said first output terminal, a second output terminal for connection to the other end of said load, means coupling said second output terminal to said supply center-tap, a voltage-amplification stage including a transistor having a direct-current feedback signal injection node and a collector, a direct-current feedback network for injecting into said node a feedback signal proportional to the direct-current potential of said junction, second circuit means direct-current coupling said voltage-amplification transistor collector to said output stage, said voltage-amplification transistor having a base electrode and an emitter electrode, a bias supply node having a relatively fixed voltage, a bias impedance extending from said bias supply node to one of said voltage-amplification transistor electrodes to supply bias current to said one electrode and to maintain the latter at an approximately constant direct-current potential, said other voltage-amplification transistor electrode constituting said feedback injection node and having said feedback network direct-current coupled thereto, and wherein said second circuit means comprises a second voltage-amplification transistor direct-current coupled to said first-recited voltage-amplification transistor, and a push-pull complementary-symmetry drive stage direct-current coupled to said second voltage-amplification transistor and said output stage, and wherein said voltage-amplification transistors are respectively of opposite polarity types with said second transistor having a base direct-current coupled to said collector of said first transistor, said bias impedance extending to said base electrode, said emitter electrode constituting said feedback injection node. 46. A transistor power amplifier as recited in
47. A transistor power amplifier comprising a single-ended push-pull output stage having a first output terminal for direct-current coupling said stage to one end of a loudspeaker or other load, a power supply connected to said output stage, a second output terminal for direct-current coupling the other end of said load to said power supply, a preceding amplifying stage comprising a transistor having a base electrode and an emitter electrode, an active network direct-current coupling said preceding stage to said output stage, a bias network maintaining one of said electrodes at a relatively fixed direct-current quiescent potential independent of variations in the load current or in the power supply potential, and a negative feedback network responsive to the potential of said first output terminal and direct-current coupled to the other electrode for applying thereto a potential proportional to the direct-current quiescent potential of said output terminal to maintain said quiescent potential substantially equal to that of said second output terminal.
48. A transistor power amplifier as recited in
49. A transistor power amplifier as recited in
transistor. 50. A transistor power amplifier as recited in claim 49 for reproduction without audible distortion by said amplifier of a high-fidelity music signal and comprising a single-ended push-pull output stage having a first output terminal for direct-current coupling said stage to one end of a loudspeaker or other load, a power supply connected to said output stage, a second output terminal for direct-current coupling the other end of said load to said power supply, a preceding amplifying stage comprising a transistor having a base electrode and an emitter electrode, an active network direct-current coupling said preceding stage to said output stage, a bias network maintaining one of said electrodes at a relatively fixed direct-current quiescent potential independent of variations in the load current or in the power supply potential, and a negative feedback network responsive to the potential of said first output terminal and direct-current coupled to the other electrode for applying thereto a potential proportional to the direct-current quiescent potential of said first output terminal to maintain said quiescent potential substantially equal to that of said second output terminal, and wherein said transistor is of a predetermined polarity type, said active network comprising a second transistor of the opposite polarity type and having a base, said first-recited transistor having a collector, first circuit means direct-current coupling said last-recited collector to said base of the second transistor, said active network including second circuit means direct-current coupling said second transistor to said output stage, and wherein said bias network maintains the base electrode of said first-recited transistor at said fixed direct-current potential, said feedback network being direct-current coupled to the emitter electrode of said first recited transistor, and wherein said second circuit means comprises a push-pull complementary-symmetry drive stage, third circuit means direct-current coupling said drive stage to said output stage, and fourth circuit means direct-current coupling said second transistor to said drive stage.
51. A transistor power amplifier as recited in
52. An amplifier as recited in
53. In combination, a pair of amplifiers each as set forth in
54. An amplifier as recited in
a quasi-output stage in cascade with and between said drive stage and said output stage, said quasi-output stage including resistive means for conducting output current from said quasi-output stage to said output terminal and then to the load at low amplifier signal levels, said resistive means having a resistance of an order of magnitude approximately the same as the order of magnitude of the resistance of the load, means normally biasing said output stage to the cutoff state at low amplifier signal levels, and means connecting said output stage to said resistive means for driving said output stage to the active state so as to supply power to the load at high amplifier signal levels.
55. An amplifier as recited in
said output stage comprising a pair of transistors each of the same polarity type as a respective one of said quasi-output stage transistors, each of said quasi-output stage transistors having an emitter, each of said output stage transistors having a base direct-coupled to a respective emitter of one of said quasi-output stage transistors, said resistive means comprising a pair of resistors each connected to a respective emitter of one of said quasi-output stage transistors.
56. An amplifier as set forth in
a second drive stage in cascade with and between said first-recited drive stage and said output stage, said second drive stage comprising four transistors, said output stage comprising four tansistors connected in series, each of said output stage transistors having a base, each of said second drive stage transistors being direct-coupled to the base of a respective one of said output stage transistors, two of said second drive stage transistors having a base, and feedback means driven by the amplifier output for driving said two second drive stage transistor bases.
57. An amplifier as set forth in
said feedback means comprises a pair of voltage divider networks each connected between the amplifier output and a respective one of the power supply terminals, each of said voltage divider networks being direct-current-coupled to a respective one of said two second drive stage transistor bases for driving the latter.
58. An amplifier as recited in
said first-recited voltage-amplification stage comprises another transistor having an emitter coupled to the emitter of said first-recited voltage-amplification transistor and having a base-emitter diode junction, said feedback network including said diode junction for injecting said feedback signal into said emitter electrode constituting said feedback signal injection node, and an input terminal connected to said base electrode of said first-recited voltage amplification stage transistor. 59. An amplifier as recited in claim 58 wherein said another transistor has a base electrode, said feedback network comprising at least a first resistor, a second resistor and a capacitor, said first feedback network resistor having one end connected to the amplifier output and its other end connected to said base electrode, a ground, said second feedback network resistor and said capacitor being connected in series between said base electrode and said ground. 60. An amplifier as recited in claim 59 wherein said bias supply node is at ground potential, said bias impedance comprising at least a resistor extending from said base electrode to ground.
61. An amplifier as recited in
an input terminal connected to said base electrode of said first-recited voltage-amplification stage transistor, said first-recited voltage-amplification stage comprises another transistor having an emitter coupled to the emitter of said first-recited voltage-amplification transistor and having a base-emitter diode, said feedback network including said diode for transmitting said feedback signal in the feedback direction to said emitter electrode constituting said feedback injection node, said drive stage comprising at least two drive transistors each having an emitter connected to the amplifier output whereby the drive and output stages operate together in the emitter-follower mode so as to present an inherently high input impedance as seen looking into the drive stage, said second voltage-amplification transistor base presenting an inherently low input impedance to the preceding first-recited voltage-amplification transistor, whereby the frequency response of the second voltage-amplification transistor rolls off at a much lower frequency than the other stages of the amplifier.
62. An amplifier as recited in
said first voltage-amplification stage transistor having a quiescent base-emitter potential difference between the base and emitter electrodes thereof, a first resistive means associated with and extending between said base electrode and ground and having a first quiescent voltage thereacross, a second resistive means associated with said emitter electrode and constituting at least part of said feedback network and having one end connected to said first output terminal and having a second quiescent voltage thereacross, said second output terminal being substantially at ground potential, network means for maintaining the quiescent potential of one of said electrodes at a level displaced from ground potential by an amount substantially equal to the sum of said quiescent base-emitter potential difference and said quiescent voltage across said resistive means associated with said other electrode to maintain the quiescent voltage of said first output terminal at substantially the same potential as said second output terminal, and means for direct-current coupling the other end of said second resistive means to said emitter electrode to transmit said feedback signal to the latter in the back direction and the voltage across said coupling means being of a magnitude to enable said first output terminal quiescent voltage to be maintained at substantially the same potential as said second output terminal.
63. An amplifier as recited in
said feedback network comprises at least a first resistor, a second resistor and a capacitor, said first resistor having one end coupled to said first output terminal, said second resistor and said capacitor being connected in series between said other end of said first resistor and ground, and wherein said drive stage presents a relatively high input impedance to said second transistor, and said second transistor presents a relatively low input impedance to said first transistor, whereby the high-frequency response of said second transistor rolls off at a lower frequency than that of said first transistor to increase the high-frequency stability margin of the amplifier, said feedback network including a feedback resistor for transmitting a feedback signal in the back direction toward said emitter electrode of said first voltage-amplification stage transistor, and conductive means distinct from said feedback resistor and connected to said emitter electrode of said first voltage-amplification stage transistor for conducting at least the major portion of the emitter current thereof.
64. A transistor power amplifier as set forth in
said output stage comprises a pair of output transistors of the same polarity type, each of said output transistors having a base, an emitter and a collector, means connecting the collector of a first of said output transistors to said power supply, means connecting the emitter of said first output transistor to said output terminal, means connecting the collector of the second output transistor to said output terminal, means connecting the emitter of the second output transistor to the power supply, means direct-current-coupling the emitter of a first of said drive stage transistors to the base of said first output transistor, and means direct-current-coupling the collector of the second drive stage transistor to the base of said second output transistor.
65. In combination, a pair of amplifiers each as set forth in
66. An amplifier as recited in
67. An amplifier as recited in
said second transistor has an output network, said dissipation-limiting protective circuit including a pair of complementary transistors each having a base, an emitter and a collector, first means connecting said protective circuit transistor collectors to said output network of said second common-emitter stage, resistive means for sensing the load current, second means connecting said bases and emitters of said protective circuit transistors to said resistive means, and a pair of resistors each having one end connected to a respective one of said protective circuit transistor bases and its opposite end connected to a node at approximately ground potential.
68. An amplifier as recited in clam 67 wherein said first connecting means comprises a pair of diodes each having one end connected to said collector of a respective one of said protective circuit transistors and its opposite end connected to said output network of the second transistor.
69. An amplifier as recited in
a quasi-output stage in cascade with and between said drive stage and said output stage, said quasi-output stage including resistive means for conducting output current from said quasi-output stage to said output terminal and then to the load at low amplifier signal levels, said resistive means having a resistance of an order of magnitude approximately the same as the order of magnitude of the resistance of the load, means normally biasing said output stage to the cutoff state at low amplifier signal levels, and means connecting said output stage to said resistive means for driving said output stage to the active state so as to supply power to the load at high amplifier signal levels.
70. An amplifier as recited in
said quasi-output stage comprises a pair of transistors, said output stage comprising a pair of transistors each of the same polarity type as a respective one of said quasi-output stage transistors, each of said quasi-output stage transistors having an emitter, each of said output stage transistors having a base direct-coupled to a respective emitter of one of said quasi-output stage transistors, said resistive means comprising a pair of resistors each connected to a respective emitter of one of said quasi-output stage transistors.
71. An amplifier as set forth in
a second drive stage in cascade with and between said first-recited drive stage and said output stage, said second drive stage comprising four transistors, said output stage comprising four transistors connected in series, each of said output stage transistors having a base, each of said second drive stage transistors being direct-coupled to the base of a respective one of said output stage transistors, two of said second drive stage transistors having a base, and feedback means driven by the amplifier output for driving said two second drive stage transistor bases.
72. An amplifier as set forth in
said feedback means comprises a pair of voltage divider networks each connected between the amplifier output and a respective one of the power supply terminals, each of said voltage divider networks being direct-current-coupled to a respective one of said two second drive stage transistor bases for driving the latter.
73. An amplifier as recited in
and an input terminal connected to said base electrode of said preceding amplifying stage transistor.
74. An amplifier as recited in
another transistor having a base and an emitter constituting said diode, said last-recited emitter being connected to said first-recited emitter electrode, said feedback network being direct-current coupled to said first-recited emitter electrode through said base and emitter of said another transistor.
77. A direct-current-coupled amplifier as set forth in
78. An amplifier as set forth in
a current-sensing resistor in series with the load and for conducting and sensing the instantaneous load current, a protective transistor having a base-emitter junction and a collector, said drive stage comprising a pair of drive transistors, one of said drive transistors having a base, a subnetwork connected to said base for transmitting an input signal to the latter whereby the A.C. signal voltage at the base is substantially the same as that at a node of the subnetwork, means connecting said protective transistor collector to said subnetwork node, a second network tending to forward-bias said protective transistor base-emitter junction in response to the magnitude of the load current flowing through said resistive means in one direction with respect to the load, and a third network tending to reverse-bias said protective transistor base-emitter junction proportional to the magnitude of the voltage swing of said other output terminal in one direction, said third network being inoperative and providing no reverse bias when said output terminals are short-circuited.
79. An amplifier as set forth in
said second network includes conductors connecting the protective transistor base to one end of said current-sensing resistor and the protective transistor emitter to the other end of said current-sensing resistor, and said third network includes a conductor network connecting the protective transistor emitter to said one output terminal to cause the voltage of said emitter to swing in the direction of the voltage swing of said one output terminal, and further including a conductive path extending from the protective transistor base to a node at approximately ground potential.
80. An amplifier as recited in
said D.C. feedback network comprises a first resistor, a second resistor and a capacitor, said first resistor having one end direct-current-coupled to said output stage midpoint and its other end direct-current-coupled to said feedback injection node, said second resistor having one end connected to said other end of said first resistor and its other end connected to one end of said capacitor, the other end of said capacitor being connected to ground, whereby said D.C. feedback network injects into said node both a D.C. feedback signal and an A.C. feedback signal with the magnitude of the D.C. feedback signal being substantially greater than the magnitude of the A.C. feedback signal, thereby minimizing the D.C. offset at said output terminals and maximizing the A.C. feedback stability of the amplifier.
81. A transistor power amplifier as set forth in
said output stage comprises a pair of output transistors of the same polarity type, each of said output transistors having a base, an emitter and a collector, means connecting the collector of a first of said output transistors to a first of said power supply terminals, means connecting the emitter of said first output transistor to said output terminal, means connecting the collector of the second output transistor to said output terminal, means connecting the emitter of the second output transistor to the second power supply terminal, means direct-current-coupling the emitter of a first of said drive stage transistors to the base of said first output transistor, and means direct-current-coupling the collector of the second drive stage transistor to the base of said second output transistor.
82. A transistor power amplifier as set forth in
a dissipation-limiting protective circuit including current-sensing resistive means in series with said output terminal and said load, a pair of complementary protective transistors each having a base-emitter junction and a collector, a pair of diodes each connecting the collector of a respective one of said protective transistors to the amplifier network extending between the collector output of the second common emitter stage and the drive stage, means tending to forward-bias a respective one of said protective transistor base-emitter junctions in response to the magnitude of the load current flowing through said resistive means in a respective direction, a node maintained at a potential approximately midway between the potentials of said power supply terminals, and first conductive means connecting the protective transistor bases to said node and second conductive means connecting the protective transistor emitters to said output stage midpoint so as to apply to a respective one of said protective transistor base-emitter junctions a voltage proportional to the voltage swing of the output stage midpoint and tending to reverse-bias said respective base-emitter junction. An amplifier as recited in claim 76 wherein said first common-emitter stage comprises another transistor of said predetermined polarity type and having a diode including as base and an emitter, said last-recited emitter being coupled to the emitter of said first-recited common-emitter stage transistor, said feedback signal being transmitted in the feedback direction through said diode. 84. A direct-current-coupled amplifier as recited in
85. An amplifier as set forth in
current-sensing resistive means in series with said other output terminal and the said load and for conducting and sensing the instantaneous load current, a pair of protective transistors of complementary polarity and each having a base-emitter junction and a collector, said second common-emitter stage transistor having a collector output network, first means connecting one of said protective transistor collectors to said collector output network of the second common-emitter stage, second means connecting the other of said protective transistor collectors to said collector output network of the second common-emitter stage, first means tending to forward-bias one of said protective transistor base-emitter junctions in response to the magnitude of the load current flowing through said resistive means in one direction with respect to the load, second means tending to forward-bias the other of said protective transistor base-emitter junctions in response to the magnitude of the load current flowing through said resistive means in the opposite direction with respect to the load, third means tending to reverse-bias said one protective transistor base-emitter junction proportional to the magnitude of the voltage swing of said other terminal in one direction, and fourth means tending to reverse-bias said other protective transistor base-emitter junction proportional to the magnitude of the voltage swing
of said other terminal in the opposite direction. 86. An amplifier as set forth in
a node maintained at approximately ground potential, said third and fourth reverse-bias means including resistive means connecting said protective transistor bases to said node.
87. An amplifier as set forth in
88. An amplifier as recited in
said first common-emitter transistor having a base electrode and an emitter electrode and having a quiescent base-emitter potential difference between said electrodes, said base bias network resistor constituting a first resistive means associated with said base electrode and having a first quiescent voltage thereacross, said center-tap being substantially at ground potential, a second resistive means associated with said emitter electrode and constituting at least part of said feedback network and having one end connected to said other output terminal and having a second quiescent voltage thereacross, network means for maintaining the quiescent potential of one of said electrodes at a level displaced from ground potential by an amount substantially equal to the sum of said quiescent base-emitter potential difference and said quiescent voltage across the resistive means associated with said other network electrode to maintain the quiescent voltage of the output at substantially ground potential, and means for direct-current coupling the other end of said second resistive means to said emitter electrode to transmit said feedback signal to the latter in the back direction and the voltage across said coupling means being of a magnitude to enable said other output terminal quiescent voltage to be maintained at substantially the same ground potential as said one output terminal.
89. An amplifier as recited in
said last-recited direct-current-coupling means comprises a diode junction, said first common-emitter stage comprising a second transistor having a base-emitter junction constituting said diode junction and having a base and an emitter coupled to the emitter of the first-recited transistor of the first common-emitter stage, said second resistive means being connected to said base of said second transistor of the first common-emitter stage.
90. An amplifier as recited in
said last-recited direct-current-coupling means comprises a direct conductive connection of the other end of said second resistive means to said emitter electrode.
92. An amplifier as recited in
said second output terminal is directly connected to said ground, a second common-emitter transistor having a base direct-current-coupled to said first transistor collector and having a collector, said second common-emitter transistor being of a polarity type opposite to that of said first transistor, each of said two drive stage transistors having a base, third circuit means direct-current-coupling said second common-emitter transistor collector to said drive stage transistor bases, and means for transmitting an input signal to said first transistor base.
94. A transistor power amplifier as set forth in
said output stage comprises a pair of output transistors of the same polarity type, each of said output transistors having a base, an emitter and a collector, means connecting the collector of a first of said output transistors to a first of said power supply terminals, means connecting the emitter of said first output transistor to said output terminal, means connecting the collector of the second output transistor to said output terminal, means connecting the emitter of the second output transistor to the second power supply terminal, means direct-current-coupling the emitter of a first of said drive stage transistors to the base of said first output transistor, and means direct-current-coupling the collector of the second drive stage transistor to the base of said second output transistor.
95. An amplifier as set forth in
said output stage comprises a pair of output transistors of the same polarity type, each of said output transistors having a base, an emitter and a collector, means connecting the collector of a first of said output transistors to a first of said power supply terminals, means connecting the emitter of said first output transistor to said output terminal, means connecting the collector of the second output transistor to said output terminal, means connecting the emitter of the second output transistor to the second power supply terminal, a push-pull emitter-follower second drive stage comprising a pair of transistors of the same polarity type as said output transistors and each having a collector, a base and an emitter, means direct-current-coupling the emitter of a one of said first-recited drive stage transistors to the base of one of said emitter-follower drive stage transistors, means direct-current-coupling the collector of the other of said first-recited drive stage transistors to the base of the other of said emitter-follower drive stage transistors, and means direct-current-coupling the emitter of each of said emitter-follower drive stage transistors to the base of a respective one of said output
transistors. 96. An amplifier as recited in
said first common-emitter stage has a high-frequency roll-off at a predetermined frequency, said second common-emitter stage having a high-frequency roll-off at a second frequency substantially lower than said predetermined frequency, whereby a large amount of feedback may be utilized with stability because of the low-frequency stability margin provided by the direct-coupling, in cooperation with the high-frequency stability margin provided by the relative respective high-frequency roll-offs of the first and second common-emitter stages.
97. An amplifier as recited in
98. An amplifier as recited in
99. A pair of amplifiers each as recited in
each of said amplifiers having individual input and output terminals so as to constitute an independent channel, means for connecting said two amplifiers either in a separate mode or in a series mode, means for connecting the output terminals of one amplifier to a first loudspeaker and the output terminals of the other amplifier to a second loudspeaker when said amplifiers are connected in said separate mode, means for transmitting a first input signal to the input of said one amplifier and a second input signal to the input terminals of said other amplifier when said amplifiers are connected in said separate mode, means for connecting an output terminal of one amplifier to one terminal of a loudspeaker and an output terminal of the other amplifier to the other terminal of the same loudspeaker when said amplifiers are connected in said series mode, and means for transmitting an input signal to the input terminals of said one amplifier and an oppositely-phased replica of said input signal to the input terminals of said other amplifier when said amplifiers are connected in said series mode.
101. A direct-current-coupled amplifier as recited in
current-sensing resistive means in series with said output terminals and said load and for conducting and sensing the instantaneous load current, a pair of protective transistors of complementary polarity and each having a base-emitter junction and a collector, means connecting each of said protective transistor collectors to a node preceding said drive stage, first means tending to forward-bias one of said protective transistor base-emitter junctions in response to the magnitude of the load current flowing through said resistive means in one direction with respect to the load, second means tending to forward-bias the other of said protective transistor base-emitter junctions in response to the magnitude of the load current flowing through said resistive means in the opposite direction with respect to the load, third means activated when the output terminals are not shorted and tending to reverse-bias said one protective transistor base-emitter junction proportional to the magnitude of the voltage swing of said first output terminal in one direction, and fourth means activated when the output terminals are not shorted and tending to reverse-bias said other protective transistor base-emitter junction proportional to the magnitude of the voltage swing of said first output terminal in the opposite direction, a node maintained at approximately ground potential, said third and fourth reverse-bias means including a conductive path connecting the protective transistor bases to said node and means connecting the protective transistor emitters to said first output
terminal. 102. An amplifier as recited in
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This application is related to my prior applications listed below:
"Transistor Power Amplifiers," Ser. No. 270,011, now U.S. Patent No. 3,281,535, filed Apr. 2, 1963; "Transistor Power Amplifiers and Feedback Speaker Systems Embodying Same," Ser. No. 311,732, andD1, including transistors and passive networks consisting solely of passive components such as conductors, resistors, capacitors and inductors. The expression "direct-current-coupled" is generic to include not merely a direct coupling but any coupling which has a conductive or direct-current transmission path, and the coupling may be either by way of a passive network or an active network including a base-emitter junction or one or more transistor stages. The term "transistor" includes any semiconductor device capable of voltage and/or current amplification, whether the device be a discrete component or part of an integrated monolithic or hybrid circuit. The expression "single-ended push-pull stage" refers to either a complementary-symmetry stage wherein the transistors are of opposite polarity types or a stage wherein both transistors are of the same polarity type. The phrase "common-emitter stage" is intended to include either a single transistor or an emitter-coupled differential pair of transistors.
It is to be understood that the various forms of invention shown in the drawings and described in detail above are merely illustrative and that numerous modifications thereof will readily occur to those skilled 2,896,029, the art without departing from the scope of the invention as delineated in the appended claims which are to be construed as broadly as permitted by the prior art.
United States Patents: 2,798,164, Stanley, Apr. 1957; 2,847,519, Aronson, Aug. 1958; 2,851,542, Lohman, Sept. 1958; 2,860,195, Stanley, Nov. 1958; 2,863,008, Keonjian, Dec. 1958; 2,896,029, Lin, July 1959; 2,955,258, Wheatley, Oct. 1960; 3,018,445, Stone, Jan. 1962; 3,023,368, Erath, Feb. 1962; 3,042,875, Higginbotham, July 1962; 3,246,251, Sheppard, Apr. 1966.
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