| 摘要 |
PROBLEM TO BE SOLVED: To provide a variable gain amplifier that implements high precision gain control.SOLUTION: A first resistance R1 is disposed between a first input terminal Pi1 and an inverting input terminal (-) of an operational amplifier 10. A second resistance R2 and a third resistance R3 are disposed in series between the inverting input terminal (-) of the operational amplifier 10 and an output terminal Po in this order. A first terminal E1 of a fourth, variable resistance R4 is connected to a node N1 of the second resistance R2 and the third resistance R3, and a second terminal E2 thereof is connected to a non-inverting input terminal (+) of the operational amplifier 10. The forth, variable resistance R4 includes a plurality (N) of resistance paths RP1-RPN disposed in parallel between the first terminal E1 and the second terminal E2. The i-th resistance path RPi includes a resistive element R4and a switch SWdisposed in series. |
