| 摘要 |
PROBLEM TO BE SOLVED: To provide a semiconductor device whose current limit value becomes constant since a forward voltage VF, i.e., a clamp voltage becomes constant by keeping the current flowing to a clamp diode constant against an increase or decrease in input voltage Vi. SOLUTION: As a current limiting means which limits the current of the clamp diode 27, a gate-source shorted depletion type MOS transistor 22 made of polysilicon on a semiconductor substrate, where an output MOS transistor 21 is formed, across an insulating film is used to make a constant current flow to the clamp diode 27 and then keep the forward voltage VF constant against an increase or decrease in specific input voltage turning on the output MOS transistor and then the clamp voltage set with the sum of forward voltages VF of three clamp diodes 27 also becomes constant, so that the source-drain current is limited to a constant current.
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