OUTPUT BUFFER

PURPOSE:To reduce the overshoot or undershoot at an output point by devising the buffer so as to supply a current only through an output transistor(TR) whose impedance is equal to that of a signal transmission line. CONSTITUTION:When an output voltage approaches a high voltage level, the output of an auxiliary control circuit G17 goes to a high level, then a TR P12 is turned off, and when an output voltage approaches a low voltage level, the output of an auxiliary control circuit 18 goes to a low level and a TR N12 is turned off, the TRs P12, N12 have a geometrical size to satisfy the delay time of the output buffer on request. That is, the low output impedance of the auxiliary output TRs P12, N12 is required for obtaining a high speed output buffer. Thus, the overshoot or undershoot caused in an output signal passing through the signal transmission line is decreased.