PURPOSE: To improve characteristics of the simulating circuit for the reverse parallel circuit of the thyristor and diode used for analog simulator.

CONSTITUTION: The simulating circuit 20 consists of a diode-incorporated N- MOSFET 21, an amplifier 22, a comparator 23, an inverter element 24, an OR element 25, a D-type flip-flop element 26, etc., and the source terminal of the MOSFET 21 is held at a reference potential; and the potential difference between the drain and source of the MOSFET 21 is amplified by an amplifier 22 and when the amplified value is plus, the MOSFET 21 is turned ON and OFF according to the high/low level of the output of the D-type flip-flop 26 inputted to the OR element 25, but when the voltage of the output of the amplifier 22 is minus, the MOSFET 21 is held ON.