Patent ID: 8278890
Filing Date: 2012-10-02
Classification: G01R,H01L,H04L

Abstract:
1. A power supply circuit comprising: a first power supply rail; a second power supply rail; a first MOSFET having a gate, a source, a drain, and a body region between the source and drain, the body region being connected so as to be at the same potential as the source, and the source and drain being connected in series with the second power supply rail, the arrangement being such that application of a suitable potential to the gate is able to switch the MOSFET to an on state in which a conductive channel is opened in the body region between the source and drain to carry a power supply current through the first MOSFET; and signal generation circuitry arranged to generate a signal indicative of a conductive state of the first MOSFET, the signal generation circuitry comprising reference voltage generation means connected to said source and arranged to generate a reference voltage, said reference voltage being a predetermined potential difference from the source potential, and a second MOSFET having a second gate, a second source, a second drain, and a second body region between the second source and second drain, the second body region being connected so as to be at the same potential as the drain of the first MOSFET, and the second gate being connected to receive said reference voltage, the arrangement being such that when the potential of the drain of the first MOSFET falls a predetermined voltage below the reference voltage the second MOSFET is switched to an on state in which a second conductive channel is opened in the second body region between the second source and the second drain, the signal being dependent upon the state of the second MOSFET.