| 摘要 |
There is disclosed a gain control amplifier wherein a signal input terminal (1) receiving an input signal (Vin) is connected to a variable resistor portion (71) including an R-2R ladder resistor group and switches (K1 to K4), and an operational amplifier (10) and resistors (r1, r2, r3) construct an adding circuit (91), which outputs an output signal (Vout) to a signal output terminal (5). Each of the switches (K1 to K4) includes terminals (A, B) and a common terminal (C) connected to one of the terminals (A, B). All of the terminals (A) arc connected to the signal input terminal (1) in common, and all of the terminals (B) are grounded in common. The ladder resistor group (R,2R) need not be of great resistance value. Thus, a gain control amplifier is achieved which is permitted to control a gain widely, finely and linearly without resistors of great resistance.
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