PURPOSE: To improve the input electrostatic dielectric strength by inserting a PNP transistor (TR) whose emitter is connected to an input terminal, whose collector is connected to a ground terminal and whose base is connected to the input terminal via a resistor.

CONSTITUTION: When a positive electrostatic voltage is applied to an input terminal 1, a collector-base junction of a TR8 of a electrostatic destruction preventing circuit provided freshly is biased reversely, and a reverse bias leakage current flows to a ground terminal 3 via a base-collector junction. Then, the said leakage current is increased with the increase in the voltage at the input terminal 1, and when the potential drop of the resistor 9 by the current reaches a forward threshold voltage between base and emitter of the TR8, the TR8 is conductive, and most of the electrostatic discharge current flowing to the input terminal flows to a ground terminal as an emitter-collector current at the conductive state of the TR8.