| 摘要 |
PURPOSE:To improve the detection sensitivity and to detect the peak value of a multipath signal and to set optionally the operation start point by converting an input voltage to a current and converting it to a DC voltage in accordance with the variable current value thereafter. CONSTITUTION:An AC input voltage vi is supplied to a voltage/current converting circuit 1 through a coupling capacity Cin and a resistance Rin and an output current Ie is obtained in the output of differential amplifiers Q1 and Q2 and the increment by which the current Ie exceeds a constant current Io is introduced from a current mirror circuit 2 as a converted current and a variable current I determined by the ratio of resistances R3 and R4 in the circuit 2 is introduced from a current/voltage converting circuit 3. Thus, a DC voltage following up the variance of the peak value of the AC input signal is obtained in the terminal To of the circuit 3 only during a period when the converted current of the circuit 1 is flowed.
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