Semiconductor integrated circuit device

Abstract

Abstract PURPOSE:To prevent occurrence of carrier injection to a substrate when an input signal is reverse voltage even if the substrate is grounded by employing a vertical pnp-junction structure formed in an integrated circuit (IC) substrate for an input protecting circuit. CONSTITUTION:A p<->-type emitter region 20 and an n-type base region 19 are sequentially formed in a p-type collector layer 1. The region 20 is connected at 9 to the gate 6 of a MOSFET 7. A signal is applied through resistance of the region 20 from a terminal 8, and clamp voltage is applied from a terminal 22. The base region 19 is now applied with 5 volts thereto, and the collector 1 is grounded. When the input signal is lower than 5 volts, the regions 20, 19 are reversely biased, and electron is not accordingly injected into the substrate 1. When the input signal exceeds 5 volts, the transistor 21 is conducted to thus protect the input. At this time holes which are not recoupled are accelerated by the 5 volts to flow into the substrate 1. When the area of the base region 19 is increased to reduce the resistance between the base region and the substrate to the ignorable degree, positive voltage is not produced at the substrate 2. Thus, the input signal is clamped at the base potential and any higher voltage is not applied to the gate 6, thus the original input is protected without error.

Inventors

• 👤 Kazuhiro Shimotori

Bibliographic Details