GATE PRPOTECTING CIRCUIT

PURPOSE:To improve the protecting function of a gate protecting circuit by connecting a semiconductor element having a withstand voltage lower than the gate breakdown voltage at the gate of a protecting transistor, thereby preventing the gate breakdown of the transistor. CONSTITUTION:When an excess input is applied to an input terminal IN, a transistor T6 instantaneously turns ON, and a transistor T5 turns On in ressponse to the voltage the obtained by substracting the threshold voltage of the transistor T6 from the input voltage. Thus, low voltage obtained by dividing the input voltage by the input resistance R and the ON resistance of the transistor T5 is applied to the gate of the transistor T, thereby performing the protection of the gate of the transistor T. Since a transistor T7 having a withstand voltage lower than the gate breakdown voltage is connected to the gate of the transistor T5 even if the input voltage is very high, the gate insulation breakdown of the T5 can be prevented in advance. In this case, since it is not necessary to form the transistor T7 so that the ON resistance is low, the size can be reduced.