Bootstrapped shunt feedback amplifier

• US 4,484,147 A
• Filed: 03/31/1983
• Issued: 11/20/1984
• Est. Priority Date: 03/31/1983
• Status: Expired due to Term

• Current Assignee: St Clair Intellectual Property Consultants Incorporated
• Original Assignee: Tektronix Incorporated (Fortive Corp.)
• Inventors: Metz, Arthur J.
• Primary Examiner(s): Mullins, James B.
• Assistant Examiner(s): Mottola, Steven J.
• Application Number:
  US06/481,024
• Time in Patent Office: 600 Days
• Field of Search: 330/76, 330/156, 330/288, 330/291, 330/292, 330/293, 330/294, 330/296, 330/311, 330/70, 330/71, 328/176
• US Class Current: 330/156
• CPC Class Codes: H03F 1/48 of aperiodic amplifiers
• CPC Class Codes: H03F 3/50 Amplifiers in which input is applied to, or output is derived from, an impedance common to input and output circuits of the amplifying element, e.g. cathode follower

Abstract

An improved bootstrapped shunt feedback amplifier is provided in which a minimum number of transistors are arranged to provide a higher slew rate of output voltage at lower power, while minimizing distortion and thus providing a more precise signal replication. Features include the use of three-terminal composite transistors to increase bandwidth and bootstrapping to improve amplifier response while reducing voltage stress on the active devices.

Claims

1. A shunt feedback amplifier, comprising:

a control stage comprising in combination a common-emitter amplifier and a common-base amplifier connected in cascode, the base of said common-emitter amplifier connectable to an input signal source and the collector of said common-base amplifier coupled to an output terminal;

a feedback path connected from said output terminal to the base of said common-emitter amplifier;

an emitter-follower stage the base of which is coupled to the collector of said common-base amplifier and the emitter of which is coupled to said output terminal;

bias means for controlling said emitter follower stage in such a manner that said emitter follower stage provides a current conduction path to develop an output signal in response to an input signal of a first polarity while maintaining a voltage difference equal to zero volts between the collector of said common-base amplifier and the emitter of said emitter follower stage, said bias means further providing a voltage difference between said collector of said common-base amplifier and the emitter of said emitter follower stage sufficient to reverse bias said emitter follower stage in response to an input signal of a second polarity; and

bootstrap means for maintaining a substantially constant collector-to-emitter voltage for said emitter follower stage.

2. A shunt feedback amplifier in accordance with claim 1 wherein said common-emitter amplifier and said emitter follower stage comprise three-terminal composite transistor devices, each consisting of first, second, and third transistors, wherein the base of said first transistor provides a first terminal, the collectors of said first and second transistors are connected together to provide a second terminal, the emitters of said second and third transistors are connected together to provide a third termnal, and the emitter of said first transistor, the base of said second transistor, and the base and collector of said third transistor are connected together.

3. A shunt feedback amplifier in accordance with claim 1 further including means for providing at least a portion of said output signal to the base of said common-base amplifier.

4. A shunt feedback amplifier in accordance with claim 3 wherein said signal providing means comprises an emitter follower transistor the base of which is coupled to receive a predetermined proportion of voltage from said feedback path, and the emitter of which is coupled to the base of said common-base amplifier.

5. A shunt feedback amplifier in accordance with claim 4 wherein said emitter of said emitter-follower transistor is connected through a resistor to a predetermined bias voltage.