Complementary metal-oxide-semiconductor input circuit

Claim 1

In a complementary metal-oxide-semiconductor circuit of the type which includes a circuit input, complementary metal-oxide-semiconductor transistors each having a threshold voltage, and an operating voltage source, the improvement of an input circuit comprising a switched resistor which is controlled from the input to define the potential at the input terminal when the same is not connected, said improvement comprising: a metal-oxide-semiconductor transistor circuit including first and second serially connected transistors connected between the circuit input and the operating voltage source, said first transistor having a gate and a first threshold voltage near the threshold voltage of one of the channel types, said second transistor having a gate and a second threshold voltage near the threshold voltage of the other channel type, said first and second threshold voltages lying in a region between the threshold voltages of the complementary metal-oxide-semiconductor transistors; and control means connected between the input and said gates and responsive to the potential at the input to operate said first and second transistors to states of conductivity which cause a potential to be defined at the input.