| 摘要 |
PURPOSE:To eliminate the need to arrange many high-accuracy resistors and to reduce the cost of a programmable gain-controlled amplifier by controlling the gain of the amplifier according to a duty ratio which is set variably by a pulse width/voltage converting circuit. CONSTITUTION:The pulse width/voltage converting circuit 6 is provided with two analog switches S1 and S2, a filter for smoothing consisting of a resistance R2 and a capacitor C2, and a duty ratio varying circuit 7 as a means for varying and setting the duty ratio T1/T2 of a pulse (e) to a necessary value. The duty ratio varying circuit 7 is connected directly to the analog switch S1 and also connected to the other analog switch S2 through an inverter 8. The output E0 of the programmable gain-controlled amplifier is controlled by the pulse width/voltage converting circuit 6 to a value corresponding to the duty ratio T1/T2 to perform control to desired gain.
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