Protective circuit device for integrated circuit

Abstract

Abstract PURPOSE:To prevent an overcurrent from flowing to a MOS transistor by clamping a voltage between a power source terminal and a ground terminal at a predetermined value. CONSTITUTION:When an overvoltage is applied to a power source terminal, it is applied to a Zener diode 4 and a diode 5, a current flowing thereto flows to an N-P-N transistor 3 and a resistor 8, and the transistor 3 is turned ON. A potential between terminals 1 and 2 is clamped at a voltage between the base and the emitter of the transistor 3 and a Zener voltage and a breakdown voltage of a diode 5, and the overcurrent further becomes the collector current of the transistor 3 to flow to the terminal 2. This clamping voltage is necessarily set to between the normal using voltage and the breakdown voltage of MOS transistors 6, 7. In order to alter the clamping voltage, the number of the diodes 4, 5 inserted between the collector and the base of the transistor 3 is altered.

Inventors

• 👤 Hiromi Miki

Bibliographic Details