| 摘要 |
PURPOSE:To compensate the distortion of a signal caused when an input signal of a VCR of an FET is large by supervising a signal inputted to a drain of the FET on a control voltage inputted to the gate of the FET. CONSTITUTION:The titled circuit is a voltage controlled variable attenuator comprising a resistor 1 and a VCR of the FET 2 connected in series and controlling the attenuation of an output signal Vo to an input signal V1 by using a control voltage Vc applied between the gate and source of the FET 5. Since the input voltage V1 is superimposed on the control voltage Vc by a capacitor 3 and resistors 4, 5, a drain-gate resistance (gammaDS) fluctuation waveform 7 is obtained corresponding to a VGS waveform 6 as the gate-source voltage based on the superimposed input signal voltage V1. In selecting the resistors 5, 4 to bring the signal level of the input signal voltage V1 superimposed on the control voltage Vc to a proper value, the VGS waveform 6 and the gammaDS fluctuation waveform 7 are operated oppositely mutually and cancelled together, its gammaDS synthesis waveform 10 is made flat to compensate the distortion of the output signal voltage Vo.
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