An exclusive-OR logic circuit based on controlled quenching of series-connected negative differential resistance devices

An exclusive-OR (XOR) logic circuit with clocked supply voltage based on the controlled quenching of series-connected negative differential resistance (NDR) devices is demonstrated. This controlled quenching process obeys a simple rule: the NDR device with the smallest peak current is always quenched first. In our present work, resonant-tunneling diodes provide the critical NDR feature, while FET's, which are integrated with RTD's in parallel, modulate the peak currents of NDR devices. The modulation of peak currents in different NDR devices directly controls the quenching sequence, and results in certain logic functions, one of which is XOR.