| 摘要 |
PURPOSE:To prevent the breakdown of a gate without degrading frequency characteristics by connecting an MISFET between a gate electrode of the MISFET and an external input terminal so that a source region and a drain region are inserted. CONSTITUTION:On a substrate 20 wherein an MOSFET25 is provided, is formed an FET30 comprising a reverse conductive type source 27, a drain 28, and a gate electrode 26. Reverse conductive impurities are doped in a channel region 29 to the FET30, and a depression type is obtained. A source electrode 31 of said FET30 is connected to the external terminal 19, a drain electrode 32 is connected to the gate electrode 22 of the FET25, and the gate electrode 26 is connected to a base electrode 33. This circuit is constituted so that VB>VM>VA, where VB is a breakdown voltage of the gate 22, VM is a voltage at which the doped region 29 is completely depleted, and VA is avalanche starting voltage of a source junction 38. In this constitution, the FET30 operates as a nonlinear resistor, the frequency characteristics are not degraded, and the gate 22 is protected from the excessive input. |
