| 摘要 |
PURPOSE:To eliminate noise with high precision to attain high precisely an output, by controlling the operating point of an operational amplifier in accordance with the level of an input signal. CONSTITUTION:Since the positive feedback quantity of an operation amplifier 1, namely, a reference voltage is changed to change the operating point of the amplifier 1 if the resistance value of a variable resistance element 8 is changed, the characteristics of the element 8 and a frequency converter 10 are matched to each other preliminarily. Operating voltages of the amplifier 1 corresponding to curves E1 and E2 are V1 and V2 in the big., and the amplifier 1 is operated near the peak value where noise hardly appears in each waveform curve, and these peak values are detected surely and the noise of waveform parts lower than respective peak values is cut off surely. Consequently, a fear of malfunction is reduced to obtain a high-precision output. |
