PURPOSE: To provide a superconduction circuit having an output driver circuit with high reliability in operation which improves the output logical amplitude of a semiconductor circuit.

CONSTITUTION: A superconduction circuit 1 performing a logical operation consists of a Josephson processing circuit 2 transmitting an output logical signal at a first logical amplitude, a voltage amplifier circuit 3 receiving the output logical signal from the Josephson processing circuit for transmitting an output signal having second logical amplitude essentially larger than the first logical amplitude, an impedance conversion circuit 4 receiving the output signal from the voltage amplifier means generating the output of the superconduction circuit at an output impedance appropriate for the signal transmission to an external circuit.