Input protective circuit

Abstract

Abstract PURPOSE:To maintain constant the input protective voltage of MOS type integrated circuit by a method wherein the temperature characteristics of Zener voltage (voltage in reverse direction) and the voltage in forward direction are maintained despite the change in ambient temperature. CONSTITUTION:When an input terminal 1 is impressed with positive sure, firstly Zener diode D1 is broken down (D2 is formed direction) to supply a resistor R1 which current; the base of transistor Tr1 is supplied with current due to the potential difference at both ends of the resistor R1 to turn the Tr1 on to protect input. On the other hand, when the input terminal 1 is impressed with negative surge, the resistor R1, the Znener diodes D2, D1 and the input terminal 1 are successively supplied with current to protect input. At this time, the higher the ambient temperature, the higher the voltage of Zener diode.D1 and the lower the voltage of Zener diode D2. Besides, the lower the ambient temperature, the lower the voltage of Zener diode D1 and the higher the voltage of Zener diode D2. Therefore, a constant protective voltage can be maintained despite change in ambient temperature.

Inventors

• 👤 Masafumi Sakamoto
• 👤 坂本　雅文

Bibliographic Details