INTERFACE CIRCUIT

PROBLEM TO BE SOLVED: To provide an interface circuit having strong resistance to electrostatic breakdown. SOLUTION: Two emitter follower circuits to become a differential couple are composed of impedance-converting transistors. The respective emitter follower circuits have three transistors Q11, Q12 and Q13 and three transistors Q21, Q22 and Q23 connected in parallel as impedance-converting transistors, and the function of the impedance-converting transistor is divided into three transistors. Since the emitter current in each of emitter follower circuit is divided by three transistors, the voltage drop of resistance is reduced to one third. Therefore, electrostatic destruction can be prevented, without having to reduce the resistance values of resistors R11-R13 and R21-R23 and a normal operation as an emitter follower circuit is also realized.