Amplifiers – With semiconductor amplifying device – Including differential amplifier
Patent
1982-12-17
1984-09-11
Mullins, James B.
Amplifiers
With semiconductor amplifying device
Including differential amplifier
330257, H03F 345
Patent
active
044713215
ABSTRACT:
An improved input current compensation circuit is provided for a superbeta transistor amplifier. The circuit has a pair of compensation transistors which simulate the amplifier transistors and support a base current which is mirrored back to the amplifier circuit to cancel the input currents thereof. The compensation transistors are supplied with base current by a control transistor. A special voltage control circuit is provided to establish controlled collector-emitter voltages for the compensation transistors independent of the control transistor, thereby decoupling the compensation transistors from the uncertain effects of the control transistor's base-emitter voltage. The control circuit is connected from the collector of one compensation transistor to the emitter of the other, and is provided with primary and secondary current sources to establish a current flow that sets up a desired bias for the control transistor and results in a near exact cancellation of input bias current. The application of the control circuit to both differential and operational amplifiers is illustrated.
REFERENCES:
patent: 4380739 (1983-04-01), Velo
Mullins James B.
Precision Monolithics, Inc.
Wan G.
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