Patent ID: 8804289

Claim:
A protection circuit for protecting an integrated circuit having a first supply rail and a second supply rail from exposure to an excessive voltage, comprising: a sensor for sensing a voltage increase on the first supply rail, the sensor having an output coupled to a signal path for providing a detection signal on said path; a clamping circuit for clamping the first supply rail to the second supply rail in response to the detection signal; a pre-amplifying stage having a control input coupled to the signal path and an output coupled to the clamping circuit; and a hold circuit for holding the control input of the pre-amplifying stage in an enabled state upon termination of the detection signal; wherein the sensor comprises a poly-Si based capacitor for storing a voltage value of the first supply rail, an amplifier for amplifying the charge stored in the poly-Si based capacitor, and a diode connected between the capacitor and the second supply rail, wherein the amplifier forms a current mirror with the diode.