Bell Telephone Laboratories

Jack K Keller

Gilbert L Mowery, Jr

A first MOS (metal-oxide-semiconductor) NOR-gate device feeding a second MOS NOR-gate device feeding an MOS output load device is arranged to yield a three output level buffer circuit, that is, whose output to a common data bus line can be 'high' ('1'), 'low' ('0'), or of very high impedance ('floating'). Each NOR-gate contains a low .beta. ('load') depletion mode type of MOS transistor and a high .beta. ('driver') enhancement mode type of MOS; the output load device contains an output driver enhancement mode type of MOS transistor and an output load MOS transistor having a threshold intermediate that of the depletion mode and enhancement mode type of MOS transistor. In this manner, only a single voltage source V.sub.DD, or typically about +5 volts in N-MOS integrated circuit technology is required to power the buffer circuit completely.

Growing community of inventors

Macungie, PA, United States of America

Jack K Keller