Patent ID: 8292185

Claim:
A circuit, comprising: an antenna configured to generate an alternating current across terminals of the antenna through electromagnetic induction based upon a received signal; a rectifier coupled to the antenna terminals and configured to receive the alternating current and generate a rectified direct current power supply voltage; and a first voltage clamp coupled to a first of the antenna terminals and a first input to the rectifier and configured to selectively sink at least some current from the first antenna terminal based upon the rectified power supply voltage from the rectifier; and a second voltage clamp coupled to a second of the antenna terminals and a second input to the rectifier and configured to selectively sink at least some current from the second antenna terminal based upon the rectified power supply voltage from the rectifier, the first and second voltage clamps each comprising a first transistor having a first transistor terminal connected to a respective first or second antenna terminal and a second transistor terminal connected to ground, a second, diode-connected transistor, and a resistor, the second transistor and the resistor connected in series between a node configured to receive the rectified power supply voltage and ground, the first and second voltage clamps each configured to turn on the respective first transistor based on a voltage across the respective series-connected second transistor and resistor, wherein an over voltage condition in the rectified power supply voltage causes the first transistor in each of the first and second voltage clamps to sink current from the respective antenna terminal.