INTERFACE CIRCUIT

PURPOSE:To eliminate a waveform distortion even when a frequency is made into a very high speed of several GHz and simultaneously, to maintain a stable characteristic by connecting a coaxial line or strip line to the emitter of a transistor to compose an emitter follower circuit and providing a resistance at a value equal to the characteristic impedance of the said line inside an IC. CONSTITUTION:In an IC 3, a resistance R01 is provided inside, and an emitter follower circuit 5-1 is provided between the resistance R01 and a differential amplifier 7. In an IC 1, an emitter follower circuit 4-1 is inserted between a differential amplifier 6 and a transistor Tr, and a resistance R02 at a value equal to a characteristic impedance R0 of a strip line 2 is provided between the emitter of the transistor Tr and the strip line 2. Thus, at the IC 3 side, the resistance R01 is made small-sized, parasite capacity and inductance are made small, the impedance to see the emitter follower circuit 5-1 from the resistance R01 is not lowered even when the frequency of the signal is made into several GHz, and the resistance value of the resistance R01 is hardly changed even when the frequency of the signal is made into the very high speed of several GHz.