PURPOSE: To obtain the semiconductor integrated circuit with sure operation and excellent reliability by preventing occurrence of a leakage current which often might be caused in a protection circuit for a MOSIC receiving a lower power supply voltage when MOS ICs whose power supply voltage differs are employed in the semiconductor integrated circuit.
CONSTITUTION: A protection circuit 21 is made up of diode-connected n-channel MOS transistors(TRs) N4/N1 connected in series. A threshold voltage of TRs (two TRs in figure 1) whose gate electrode connects to an external terminal 6 is set higher than a threshold voltage of MOS TRs in an internal circuit 3. Furthermore, an external signal VIN is delivered to the internal circuit 3 via an n-channel MOS TR N5 as a transfer gate.
ITOU TAKAHARU
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