Circuit and method of varying amplifier gain

Details Circuit and method of varying amplifier gain Circuit and method of varying amplifier gain

1994-10-11

1995-11-14

Mullins, James B.

Amplifiers

With semiconductor amplifying device

Including differential amplifier

330278, 330307, H03F 345, H03G 330

Patent

active

054670578

ABSTRACT:
A variable gain amplifier (10) provides a controllable amplification of an input signal as determined by a gate voltage. The variable gain amplifier takes on the form of a differential amplifier with first and second emitter-coupled lateral NPN bipolar transistors (12, 26) each having a gate (60) spanning the base region (48). The bases of the first and second transistors are biased with resistors (20-22, 30-32) coupled between V.sub.cc and ground potential. The gate voltage effects the conductivity through the base region and provides control over the forward current gain of the transistors. A third lateral NPN bipolar transistor (70) is added in parallel with the first transistor and operates with a separate gate voltage to provide two modes of amplification.

REFERENCES:
patent: 3322970 (1967-05-01), Batteau
Ayers et al., "PNP-Junction Field-Effect Transistor," IBM Technical Disclosure Bulletin, vol. 19, No. 3, Aug. 1976 pp. 984-985.

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