PURPOSE: To obtain the circuit constitution where the amplification factor is varied continuously by using a varactor element as a capacitive element of a switched capacitor circuit.
CONSTITUTION: The capacitance between the anode and cathode is decreased in a varactor diode C44 when the reverse voltage is increased. Thus, a signal controlled by a switch S42 allows the diode C44 to act like a coupling capacitor separating the signal from a control voltage and a resistor R44 prevents this signal from being leaked to a control voltage input terminal CT4. When a prescribed control voltage is applied from this terminal CT4, the diode C44 acts like a capacitor with a prescribed capacitance value. Thus, the capacitance value controlled by the switch S42 is a combined capacitance value of series connection between a capacitor C43 and the diode C44. Thus, in changing continuously the control voltage, since the diode C44 is also changed continuously, the coefficient is changed continuously.
YAGI SHIZUO
MATSUMOTO SHIYUUZOU
