| 摘要 |
PURPOSE:To realize a semiconductor circuit that is useful in measuring by means of external terminals the threshold values of internal MIS field effect transistors and serves as a protecting circuit as well by a method wherein MIS field effect transistors of the first and second conductivity types are provided with their sources connected to the first and second power supplies and the gates and drains to input and output terminals. CONSTITUTION:Terminals 12-15 are potentially tantamount to the ground GND, and a potential higher than the ground GND is applied to an input terminal 1, whereunder only a MIS field effect transistor 2 is turned on for the threshold values to be measured of the transistor 2. Under the ordinary conditions where a power source voltage Vcc is applied to the terminals 12, 14 and the ground potential GND to the terminals 13, 15, a positive direction surge voltage generated at the input terminal 1 results in a forward direction operation of a diode between the drain 8 of a transistor 7 and an island region 11. Under such conditions, the transistor 2 is turned on, allowing the positive direction surge voltage into the Vcc terminal 12. |
