SEMICONDUCTOR DEVICE AND CONSTANT-VOLTAGE CIRCUIT

摘要

PROBLEM TO BE SOLVED: To prevent damage to the gate oxide film of a lateral DMOS transistor. SOLUTION: The P-channel lateral DMOS transistor 5 as an output transistor is installed across an input terminal 1 and an output terminal 3. A protective diode 11 is connected across the gate electrode interconnection of the transistor 5 and the source of the transistor 5. The protective diode has a reverse breakdown strength which is about half the gate-oxide-film breakdown voltage of the transistor 5. When the voltage of the gate electrode interconnection of the transistor 5 becomes about half the gate-oxide-film breakdown voltage of the transistor 5, the protective diode 11 is broken down, droppage in the voltage of the gate-electrode interconnection is prevented, and damages to the gate oxide film of the transistor 5 is prevented.