| 摘要 |
PROBLEM TO BE SOLVED: To provide a variable capacitance circuit with on/off-switch of variable capacitance function. SOLUTION: The variable capacitance circuit includes a CMOS variable capacitance circuit 1 having paired CMOS transistors M1-M2, M3-M4, and M5-M6 multi-stage connected in parallel, a stepwise DC potential forming circuit 2 for forming a bias voltage of a distinct voltage value by voltage dividing a constant voltage power Vcc by resistors R7-R9 and supplying the bias voltages to bases of CMOS transistors M1-M6 of the respective stages, and a p-channel FETM 7 for controlling the on/off of the supply of the constant voltage power Vcc to the circuit 2. At the variable capacitance function on time, the FETM 7 is turned on. The bias voltages from the circuit 2 is supplied to the bases of the transistors M1-M6, and variably controlled to capacitance values according to the control voltage from a terminal 3. At the variable capacitance function on time, the FETM 7 is turned off, the bases of the transistors M1-M6 are grounded, and the respective capacitance values are controlled to the minimum capacitance values. COPYRIGHT: (C)2006,JPO&NCIPI
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