Logic circuit

Abstract

A logic circuit which reduces occurrence of breakdown of the pull-down transistor and pull-up transistor in the output stage when a high voltage is applied to the power supply line and ensures high voltage resistance. The logic circuit controls a pull-up transistor provided between a first power supply and an output terminal which turns ON and OFF in accordance with a collector voltage of a phase splitter transistor and controls the pull-down transistor provided between the second power supply and output terminal with an emitter voltage. Breakdown of the pull-down and pull-up transistors can be reduced and a high voltage resistance ensured by providing a protection circuit which discharges the base of the pull-down transistor and turns OFF the pull-down transistor by detecting when a voltage difference between the first power supply and the second power supply exceeds a specified value.