EQUIVALENT RESISTANCE CIRCUIT

PURPOSE:To set a desired resistance value with high accuracy regardless of characteristic parameters (beta0, W/L, etc.), by using an MOS transistor as an equivalent resistance. CONSTITUTION:Insulated gate type field effect transistors MOSFETQ1 and Q2 are constituted with the same conditions with substantially equal characteristic parameters (W/L, beta0, etc.). Therefore the working point of the FETQ2 is set at a point P when the gate-source voltage VGS3 is applied to a gate. Therefore the resistance value of the FETQ1 is substantially equal to that of the FETQ2 when viewed from the drain, i.e., a point Z'. Then the equivalent resistance of the desired value can be obtained regardless of the characteristic parameters W/L, beta0, etc. of both FETQ1 and Q2 by setting properly a constant current I0 and the reference voltage VREF. Then the point P can be set optionally by controlling at least one of the voltage VREF and the current I0. As a result, it is possible to control the impedance, i.e., the equivalent to a desired level.