INPUT BUFFER CIRCUIT

PURPOSE:To prevent the logic-functional malfunction of a semiconductor device due to a wrong signal transmitted to the internal circuit of the semiconductor device by providing a circuit which detects the occurrence of power supply noise and another circuit which detects the occurrence of ground noise in the input buffer circuit of the semiconductor device. CONSTITUTION:This input buffer circuit is constituted of a pad 1, protective circuit 2, NAND circuits 3-5, voltage comparator circuits 6 and 7, and OR circuit 8 in corresponding to a power supply line 201 and ground conductor 202. The voltage comparator circuits 6 and 7 detect the occurrence of power supply noise by comparing their own potentials with a reference power supply potential in a state where no power supply noise exists and the occurrence of ground noise by comparing their own ground potentials with a reference ground potential in a state where no ground noise exists. Therefore, the occurrence of such a case that the logical value of an input signal is wrongly decided and a wrong signal is transmitted to a circuit in a semiconductor device can be prevented even when variation of a power supply potential or ground potential occurs in the power supply or ground line of this input buffer circuit.