| 摘要 |
PURPOSE:To surely protect an integrated circuit from an input by protecting a device from an input signal such as the external surge with a voltage lower than the gate withstand voltage of a C-MOS circuit, and moreover by adjusting a voltage to be applied to the gate. CONSTITUTION:When an input signal IN is supplied to an input protection circuit, the signal IN is supplied to a C-MOS circuit 18 through a resistor R1, N<+> layers 12, 21 are formed on the surface of substrate 11, since the N<+> layers 12, 21 are isolated with specified interval a depletion layer is formed on the surface of the substrate 11, the punch-through is generated between such N<+> layers 12 and 21 and a diode circuit 31 becomes conductive (ON state). Accordingly, the backward breakdown voltage of diode circuit 31 can be lowered than the gate breakdown voltage of C-MOS 18. In adition, the signal IN which is higher than the gate breakdown voltage is supplied to the gate of C-MOS circuit 18 before the diode circuit 31 turns ON and thereby the breakdown of gate can be prevented. |
