Transistor series amplifier

• US 3,887,878 A
• Filed: 03/04/1974
• Issued: 06/03/1975
• Est. Priority Date: 03/04/1974
• Status: Expired due to Term

• Current Assignee: Otto Heinrich Jr. Schade
• Original Assignee: Otto Heinrich Jr. Schade
• Inventors: Schade, Otto Heinrich Jr.
• Primary Examiner(s): Mullins, James B.
• Application Number:
  US05/447,934
• Time in Patent Office: 456 Days
• Field of Search: 330/13,15,17,18,20,22,40
• US Class Current: 330/267
• CPC Class Codes: H03F 3/3071 with asymmetrical driving of the end stage
• CPC Class Codes: H03F 3/3076 with symmetrical driving of the end stage

Abstract

Bias for the n cascade connected output transistors of a conventional series amplifier is obtained by applying successive increments, each 1/n times the output voltage available across the series connected conduction paths of these transistors to the control electrodes of the successive transistors in the cascade, except for the one connected to the load terminal. Drive signal is applied to the control electrode of this transistor. In accordance with the present invention, the drive signal is supplied via n cascade connected input transistors biased in similar fashion to the cascade connected output transistors, to develop across its conduction path a voltage approximately equal to 1/n times the amplifier output voltage. This way of applying drive signal to the series amplifier facilitates its connection with another series amplifier in push-pull amplifier configurations.

Claims

1. An amplifier comprising:

first and second terminals;

a first plurality of transistors ordinally numbered first through last, all of the same conductivity type, each having an input electrode and having common and output electrodes with a variably conductive path therebetween responsive to signal between its input and common electrodes, said variably conductive paths thereof being serially connected in a first succession determined according to the numbering of the transistors, said first successiOn being connected between said first and said second terminals so the common electrode of the first transistor thereof is connected to said first terminal and so the output electrode of the last transistor thereof is connected to said second terminal;

a second plurality of transistors, ordinally numbered first through last, at least those following the first being of opposite conductivity type to those of said first plurality, each having an input electrode and each having common and output electrodes with a variably conductive path therebetween responsive to signal between its input and common electrodes, said variably conductive paths thereof being serially connected in a second succession determined according to the numbering of the transistors, said second succession being connected between said second terminal and the input electrode of said first transistor of said first plurality with the output electrode of the last transistor in said second plurality connected to the input electrode of the first transistor of said first plurality;

means for apportioning the potential appearing between saidd first and said second terminals and applying the successive portions thereof to the input electrodes of the successive transistors following said first transistor in said first succession, thereby to secure by the common electrode follower action of the transistors following said first transistor in said first succession substantially equal potentials across the variably conductive paths in said first succession, and for apportioning the potential appearing between said second and said first terminals and applying the successive portions thereof to the input electrodes of the successive transistors following the first transistor in said second succession thereby to secure by the common electrode follower action of the transistors following said first transistor in said second succession substantially equal potentials across the variably conductive paths in said second succession; and

means for applying an input signal between the input and common electrodes of said first transistor of said second plurality.

2. An amplifier as set forth in claim 1 wherein said first transistor of said second plurality is of the opposite conductivity type to those of said first plurality and is connected in a common-emitter amplifier configuration.

3. An amplifier as set forth in claim 1 wherein said first transistor of said second plurality is of the opposite conductivity type to those of said first plurality and is connected in a common-base amplifier configuration..

4. An amplifier as set forth in claim 1 wherein said means for apportioning the potential appearing between said first and said second terminals and applying the successive portions thereof to the input electrodes of the successive transistors following said first transistor in said first succession and for apportioning the potential appearing between said second and said first terminals and applying the successive portions thereof to the base electrodes of the successive transistors following the first transistor in said second succession comprises:

a potential divider having an input circuit connected between said first and said second terminals and having a plurality of output taps respectively connected to separate ones of the input electrodes of the transistors in said first and said second pluralities except the first transistors in both of said first and said second pluralities.

5. An amplifier as set forth in claim 4 further including:

an auxiliary transistor having an input electrode and having common and output electrodes with a variably conductive path therebetween, responsive to signal between its input and common electrodes, the variably conductive path of said auxiliary transistor being connected between said first terminal and the input electrode of the last transistor of said second plurality, the input electrode of said auxiliary transistor being connected to a point in said firsT succession, whereby an increase of the conductivity of the variably conductive paths in said first succession above a predetermined level causes the variably conductive path of said auxiliary transistor to become conductive thereby to alter the division ratio of said potential divider with respect to the base potential of the second transistor of said second plurality to raise the potential across the variably conductive path of said first transistor of said second plurality.

6. An amplifier comprising:

first and second terminals;

a first plurality of transistors ordinally numbered first through last, all of the same conductivity type, each having an input electrode and having common and output electrodes with a variably conductive path therebetween responsive to signal between its input and common electrodes, said variably conductive paths thereof being serially connected in a first succession determined according to the numbering of the transistors, said first succession being connected between said first and said second terminals so the common electrode of the first transistor thereof is connected to said first terminal and so the output electrode of the last transistor thereof is connected to said second terminal;

a second plurality of transistors, numbered first through last, at least those following the first being of opposite conductivity type to those of said first plurality, each having an input electrode and each having common and output electrodes with a variably conductive path therebetween responsive to signal between its input and common electrodes, said variably conductive paths thereof being serially connected in a second succession determined according to the numbering of the transistors, said second succession being connected between said second terminal and the input electrode of said first transistor of said first plurality with the collector electrode of the last transistor in said second plurality connected to the input electrode of the first transistor of said first plurality;

means for apportioning the potential appearing between said first and said second terminals and applying the successive portions thereof to the base electrodes of the successive transistors following said first transistor in said first succession thereof, thereby to secure by the common electrode follower action of the transistors following said first transistor in said first succession substantially equal potentials across the variably conductive paths in said first succession, and for apportioning the potential appearing between said second and said first terminals and applying the successive portions thereof to the base electrodes of the successive transistors following the first transistor in said second succession, thereby to secure by the common electrode follower action of the transistors following said first transistor in said second succession substantially equal potentials across the variably conductive paths in said second succession; and

means for supplying a current to the input electrode of said first transistor of said second plurality.

7. An amplifier comprising:

first and second terminals for connection to a power supply;

a third terminal for connection to a load;

a first plurality of transistors of a first conductivity type ordinally numbered first through last, each having an input electrode and having common and output electrodes with a variably conductive path therebetween responsive to signal between its input and common electrodes, their variably conductive paths being serially connected in order of their numbering between said third and said first terminals, so the common electrode of the first transistor is connected to said third terminal and so the output electrode of said last transistor is connected to said first terminal;

a second plurality of transistors, numbered first through last, at least those following the first being of a second conductivity type complementary to the first conductivity type, each having an input electrode and having common and output electrodes with a variably conductive path therebetween responsive to signal between its input and common electrodes, said variably conductive paths thereof being serially connected in order of their numbering between said first terminal and the base electrode of said first transistor of said first plurality, so the collector electrode of the last transistor in said second polarity is connected to the base electrode of the first transistor of said first plurality;

a third plurality of transistors of said second conductivity type, ordinally numbered first through last, each having an input electrode and having common and output electrodes with a variably conductive path therebetween responsive to signal between its input and common electrodes, said variably conductive paths thereof being serially connected in order of their numbering between said third and said second terminals, so the common electrode of the first transistor thereof is connected to said third terminal and so the output electrode of the last transistor thereof is connected to said second terminal;

a fourth plurality of transistors, numbered first through last, at least those following the first being of said first conductivity type, each having an input electrode and each having common and output electrodes with a variably conductive path therebetween responsive to signal between its input and common electrodes, said variably conductive path thereof being serially connected in order of their numbering between said second terminal and the base electrode of said first transistor of said third plurality, so the collector electrode of the last transistor in said fourth plurality is connected to the base electrode of the first transistor of said third plurality;

means for applying bias to the input electrodes of the first transistors in said second plurality and in said fourth plurality;

means for applying an input signal between the input and common electrodes of at least one of the first transistors in said second plurality and in said fourth plurality;

a first potential divider having an input circuit connected between said first and said third terminals and having a plurality of output taps each connected to a respective one of the base electrodes of the transistors in said first and said second pluralities except the first transistors thereof, thereby to apportion substantially equal potentials to the variable conductivity paths of the transistors in said first plurality and substantially equal potentials to the variable conductivity paths of the transistors in said second plurality; and

a second potential divider having an input circuit connected between said second and said third terminals and having a plurality of output taps each connected to a respective one of the base electrodes of the transistors in said third and fourth pluralities except the first transistors thereof, thereby to apportion substantially equal potentials to the variably conductive paths of the transistors in said third plurality and substantially equal potentials to the variably conductive paths of the transistors in said fourth plurality.

8. An amplifier as set forth in claim 7 having:

direct current conductive means connected between the base electrodes of the first transistors of said first and said third pluralities of transistors for establishing quasi-linear operation thereof.

9. An amplfier as set forth in claim 7 wherein at least one of the first transistors of said second and said fourth pluralities is of the same conductivity type as the rest of the transistors in that plurality and is connected in a common-emitter amplifier configuration.

10. An amplifier comprising:

first and second terminals for connection to a power supply;

a third terminal for connection to a load;

a first plurality of transistors of a first conductivity type, ordinally numbered first through last, each having an input electrodE and having common and output electrodes with a variably conductive path therebetween responsive to signal between its input and common electrodes, their variably conductive paths being serially connected in order of their numbering between said third and said first terminals with the common electrode of said first transistor connected to said first terminal and the output electrode of said last transistor connected to said third terminal;

a second plurality of transistors, ordinally numbered first through last, each being of a second conductivity type complementary to the first conductivity type, each having an input electrode and having common and output electrodes with a variably conductive path therebetween responsive to signal between its input and common electrodes, said variably conductive paths thereof being serially connected in order of their numbering so the output electrode of the last transistor in said second plurality is connected to the input electrode of the first transistor of said first plurality, the input electrode of said first transistor of said second plurality being connected to said third terminal;

a third plurality of transistors of said first conductivity type, ordinally numbered first through last, each having an input electrode and having a common and an output electrodes with a variably conductive path therebetween responsive to signal between its input and common electrodes, said variably conductive paths thereof being serially connected in order of their numbering between said third and said second terminals so the common electrode of the first transistor thereof is connected to said third terminal and so the output electrode of the last transistor thereof is connected to said second terminal;

a fourth plurality of transistors, ordinally numbered first through last, at least those following the first being of said second conductivity type, each having an input electrode and having a common and output electrodes with a variably conductive path therebetween responsive to signal between its input and common electrodes, said variably conductive paths thereof being serially-connected in order of their numbering between said second terminal and the base electrode of said first transistor of said third plurality so that the collector electrode of the last transistor in said fourth plurality is connected to the base electrode of the first transistor in said third plurality;

a fifth plurality of transistors, ordinally numbered from first to last, at least those following the first being of said second conductivity type, each having an input electrode and having common and output electrodes with a variably conductive path therebetween responsive to signal between its input and common electrodes, said variably conductive paths thereof being serially connected in order of their numbering so that the output electrode of the last transistor in said fifth plurality is connected to the common electrode of the first transistor in said second plurality;

means for applying a signal between the input and common electrodes of the first transistor in said fourth plurality;

means for supplying a signal between the input and common electrodes of said first transistor in said fifth plurality;

a first potential divider having an input circuit connected between said first and said third terminals and having a plurality of output taps each connected to a respective one of the base electrodes of the transistors in said first and said second pluralities except for their respective first transistors, thereby to apportion substantially equal potentials to the variably conductive paths of the transistors in said first plurality and substantially equal potentials to the variably conductive paths of the transistors in said second plurality;

a second potential divider having an input circuit connected between said third and said second terminals and having a plurality of output taps each connected to a respective one of the base electrodes of tHe transistors in said third and said fourth and said fifth pluralities except for their respective first transistors, thereby to apportion substantially equal potentials to the variably conductive paths of the transistors in said third plurality and substantially equal potentials to the variably conductive paths of the transistors in said fourth and said fifth transistors.

11. An amplifier as set forth in claim 10, wherein the first transistors of said fourth and said fifth pluralities are each of said second conductivity type, one of them being connected in common-base amplifier configuration to receive an input signal applied to its common electrode and the other of them being connected in common-emitter amplifier configuration to receive an input signal applied to its input electrode.

12. In combination:

a series amplifier comprising a first cascade of transistors, the principal conduction paths of which are connected in a first serial connection for direct current, and a potential divider for apportioning the potential appearing across said first serial connection to the control electrodes of all but the first transistors in said first cascade to cause the transistors in said first cascade to have substantially equal potentials across their principal conduction paths; and

a second cascade of transistors, the principal conduction paths of which are in a second serial connection for direct current, and sharing said potential divider with said first series amplifier for apportioning the potential appearing across said first serial connection to the control electrodes of all but the first transistor in said second cascade to cause the transistors in said second cascade to have substantially equal potentials across their principal conduction paths, said second serial connection being connected to the control electrode of the first transistor of said first cascade thereby to cascade said first cascade after said second cascade.

13. In combination:

an input transistor, an inverting amplifier transistor of a first conductivity type, a first number at least one of transistors of said first conductivity type and a second number at least one of transistors of a second conductivity complementary to the first, each of said transistors havivng a control electrode and a variably conductive principal conduction path between a pair of other electrodes;

a potential divider having first and second input terminals and a plurality of output taps;

a first serial connection, of the principal conduction paths of said inverting amplifier transistor and said first number of transistors, being connected between the input terminals of said potential divider, with the principal conduction path of said inverting amplifier transistor being the one most closely connected to the first input terminal of the potential divider;

a second serial connection of the principal conduction paths of said input transistor and said second number of transistors being connected between the second input terminal of said potential divider and the control electrode of said inverting amplifier transistor;

means for connecting a respective one of the output taps of said potential divider to each of the control electrodes of said first number of transistors to apportion thereto the potential between the input terminals of said potential divider, thereby to cause substantially equal potentials across the principal conduction paths in said first serial connection; and

means for connecting a respective one of the output taps of said potential divider to each of the control electrodes of said second number of transistors to apportion thereto the potential between the input terminals of said potential divider, thereby to cause substantially equal potentials across the principal conduction paths in said second serial connection.

14. A series amplifier comprising, in combination:

first and second terminals;

n, where n is an integer, outpuT transistors of the same conductivity type in a first cascade connection, each having common and output electrodes with a conduction path therebetween and having a control electrode for controlling the conductance of its conduction path, said conductio paths thereof being connected in series between said first and said second terminals, whereby when said transistors conduct a voltage V appears between said first and said second terminals;

n input transistors in a second cascade connection, each having common and output electrodes with a conduction path therebetween and having a control electrode for controlling the conductance of its conduction path, said conduction paths thereof being connected in series between said second terminal and the control electrode of the output transistor connected to the first terminal;

means responsive to the voltage V appearing between said first and said second terminals for applying successive increments thereof, each of amplitude V/n, to the control electrodes of all but the first of the n output transistors in said first cascade connection in the order of their succession therein, and to the control electrodes of all but the first of the n input transistors in said second cascade connection in the order of their succession therein; and

means for applying an input signal between the control electrode of the input transistor included in said second cascade connection and its electrode connected to said second terminal.

15. A series amplifier as set forth in claim 14 wherein said means responsive to said voltage comprises a voltage divider with n-1 taps, each tap connected to one output transistor control electrode and to one input transistor control electrode.

16. A series amplifier as set forth in claim 14 arranged in push-pull amplifier configuration with another transistor amplifier of the same type but with complementary conduction characteristics, their input signal terminals arranged for receiving push-pull input signals, their first terminals connected together for supplying a signal responsive to said push-pull input signals, their second terminals arranged for receiving an operating potential therebetween.

17. A series amplifier as set forth in claim 14 arranged in push-pull amplifier configuration with another transistor amplifier of the same type but with complementary conduction characteristics, their first terminals being connected together and their output transistors connected to their respective first terminals having their control electrodes direct current conductively coupled to each other.