| 摘要 |
PURPOSE:To prevent the lowering of withstanding voltage against a high-voltage power supply terminal (a Vpp terminal), and to obviate even the breakdown of a transistor by utilizing a diode, which has MOS structure and a gate thereof is controlled, and changing the breakdown voltage of the diode according to the state of the non-application of a power supply and application thereof. CONSTITUTION:A high-voltage power supply Vpp terminal 5 is connected to a gate for a diode D1 through a depletion type transistor 11, and the gate is grounded through a capacitance 12. With the titled circuit, approximately Vpp is applied to the diode D1 through the transistor 11 when voltage for a program such as 20V is applied to the Vpp terminal 5, breakdown voltage rises, and it is not broken down up to the withstanding voltage of Vpp, Vpp=20V or more. When surge voltage is applied to the Vpp terminal 5, on the other hand, an internal circuit is protected because the gate voltage of the diode D1 rises only slowly by the transistor 11 and the capacitance 12. |
