HALF WIDTH VARIABLE CIRCUIT

PURPOSE:To change a half value width in an ultra high-speed area such as a Gb/s by outputting the amplitude of a digital input signal in changing it to a prescribed amplitude in an amplitude variable circuit and inputting the output of the amplitude variable circuit and an output to invert the output in a switching circuit. CONSTITUTION:An input signal 1' and an inverted input signal 2' from an amplitude variable circuit 40 are given to an emitter follower circuit in two stages composed of Trs 50, 55 and 60, 65, the shift of a voltage is executed, and the emitter outputs of the Trs 55 and 65 are given to respective bases of Trs 70 and 80 of a current switching circuit 90. As a result, according to the difference in input amplitude, the signal response of the current switching circuit is made different, and a time width, in which positive/inverted output signals are crossed, is made different. Namely, at the time of input voltages V1 and V2, the half value widths of the output signals are made into W'1 and W'2.