Input circuit operable under different source voltages in semiconductor integrated circuit

摘要

An input circuit provided in a MOS semiconductor IC having a compatible characteristics with an external TTL circuit. The input circuit comprises a circuit for generating a fixed reference voltage without depending on any supplied source voltage level, and a circuit for comparing the input voltage with the reference voltage. Therefore, a fixed margin for detecting the logic value of the input signal can be ensured regardless of whether the source voltage supplied is either 3.0 volts or 5.0 volts.