A CMOS output driver includes an n-channel low threshold device in series between a p-channel transistor and an output terminal. Under normal driver operation, the low threshold transistor drops essentially zero volts and is imperceptible in the circuit. However, under special mode conditions when high...http://www.google.fr/patents/US5057715?utm_source=gb-gplus-shareBrevet US5057715 - CMOS output circuit using a low threshold device
