Patent ID: 8395870

Claim:
An input/output circuit for an LSI circuit having an external connection pad, comprising: an input circuit connected to the external connection pad; and an output circuit connected to the external connection pad, wherein the output circuit includes a first and a second N-channel MOS transistor provided between the external connection pad and a ground line of the LSI circuit, and connected together in series, where the first N-channel MOS transistor is closer to the external connection pad and the second N-channel MOS transistor is closer to the ground line, and an output transistor bias generation circuit configured to supply, to the gate of the first N-channel MOS transistor, a voltage which is determined by a voltage of the external connection pad and a voltage of a power supply line of the LSI circuit, and the output transistor bias generation circuit includes a first diode element provided between the external connection pad and the gate of the first N-channel MOS transistor, a second diode element provided between the gate of the first N-channel MOS transistor and the ground line, a third diode element provided between the power supply line and the gate of the first N-channel MOS transistor, and a capacitive element provided between the gate of the first N-channel MOS transistor and the ground line.