Gaas mesfet logic circuits including push pull output buffers

Abstract

The present invention relates to a family of new GaAs MESFET logic circuits including push pull output buffers, which exhibits very strong output driving capability and very low power consumption at fast switching speeds. A 3 way OR/NOR circuit of this invention includes a standard differential amplifier, the first branch of which is controlled by logic input signals. The second branch includes a current switch controlled by a reference voltage. The differential amplifier provides first and second output signals simultaneously and complementary each other. The circuit further includes two push pull output buffers. The first output buffer comprises an active pull up device connected in series with an active pull down device, and the first circuit output signal is available at their common node or at the output terminal. The active pull up device is controlled by a first output signal of the differential amplifier, and the active pull down device is preferably controlled by the second output signal through an intermediate source follower buffer. The second output buffer is of similar structure. The depicted circuit is of the dual phase type. However, if only one phase of the circuit output signal is needed, the output buffer and the intermediate buffer can be eliminated. The number of devices can be even further reduced by eliminating the other remaining intermediate buffer.