Transistor output circuit, semiconductor device including transistor output circuit, and switching electric power unit having transistor output circuit

Abstract

A main driver, in which NPN and PNP bipolar transistors are connected in series, is driven by an output of a pre-driver having a first CMOS circuit driven by an input signal. An assist circuit having a second CMOS circuit driven by the input signal and also having a current limit resistor is provided, and an output of the main driver is assisted by an output of the assist circuit. Therefore, it is possible to reduce a short circuit current in a transistor output circuit, to increase and decrease an output signal to an power-supply potential (upper limit) and a ground potential (lower limit), and to smoothly change the output signal near the power-supply potential and the ground potential. Further, an intensity of electromagnetic noise is reduced and a switching output having a sufficiently large amplitude is supplied.