Integrated protection circuit against the forward biasing of the input junction in digital MOS ICs

The paper presents a technique which prevents carrier injection into the substrate caused by a large negative-going signal applied to an AC-coupled input amplifier in digital MOS integrated circuits. The analysis of the phenomena and computer simulations of the proposed protection circuit are studied, showing that the injected charge is reduced to about 1 pC when the external coupling-capacitor charge C ¿V is equal to about 10 nC. Experimental data are shown for this circuit, which was used in an n-MOS infrared remote-control receiver IC.