| 摘要 |
An input buffer having a differential amplifier 3 includes a protection circuit 4 located between an input terminal 1 and the differential amplifier. The protection circuit serves to protect a MOS transistor 5 constituting the differential amplifier when a high voltage is applied to the input terminal of the input buffer. The protection circuit is an N-channel type MOS transistor with a drain electrode connected to the input terminal, a source electrode connected to a gate terminal of the MOS transistor 5 constituting the differential amplifier 3 and a gate terminal supplied with a power source voltage Vcc. In this configuration, the input buffer prevents occurrence of an unnecessary through current.
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