High swing interface stage

Abstract

An integrated CMOS high swing interface output stage which can transmit and receive data from other devices which may include devices operating from a different, particularly a higher, voltage power supply. The interface utilizes three P-channel devices in a common well on the substrate and three N-channel devices in another common well on the substrate. Two of the three P-channel devices are connected in series between the positive power supply terminal and the output of the interface and two of the N-channel devices are connected in series between the output of the interface and a negative power supply terminal. The third P-channel device is connected between the common connection of all three P-channel devices and the local substrate and the gate of the P-channel device which is connected to the positive power supply terminal. The third N-channel device is similarly connected between the common connection of all three N-channel devices and the respective local substrate and the gate of the N-channel device connected to the negative power supply terminal. Appropriate control of all six devices provides free swinging of the output beyond the range of the power supply when not powered and when powered but inactive, while providing drive of the output when the interface is active.