| 摘要 |
PROBLEM TO BE SOLVED: To provide a gain control circuit and a class D power amplifier circuit, which are stably applied for gain control and wide-range voltage sources. SOLUTION: The gain control circuit 100 includes a signal input terminal 102 in which an analog input signal is input, a calculation amplifier 108 which amplifies analog signal to be supplied with a voltage source E1, and a first T-type resistance circuit T123 which is connected between an inversion input terminal 108a of the calculation amplifier 108 and an output terminal 108c. A first variable resistor RV1 for gain control is connected between the signal input terminal 102 and the inversion input terminal 108a. A DC bias voltage is supplied to a non-inversion input terminal 108b of the calculation amplifier 108 from a bias voltage supply circuit 130. The bias voltage supply circuit 130 includes a first voltage generation circuit 132 and a second bias voltage generation circuit 138. The first bias voltage generation circuit 132 includes a second voltage source E2 and a second T-type resistance circuit T123a. The second bias voltage generation circuit 138 includes a third voltage source E3 and a second variable resistor RV2. COPYRIGHT: (C)2010,JPO&INPIT
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