Patent ID: 9143092
Filing Date: 2015-09-22
Classification: H03F,H03K,H03M

Abstract:
1. A method of differential signal transfer from a differential input Vinp and Vinn when a common mode input voltage is higher than the power supply voltage, comprising: providing an input chopper having first through fourth chopper transistors, each having a source, a drain and a gate, the input chopper having Vinp and Vinn as a differential input, the first through fourth transistors being MOS transistors, and wherein the sources of the first and third transistors are coupled to the Vinp input, the sources of the second and fourth transistors are coupled to the Vinn input, the drains of the first and fourth transistors are coupled to input chopper output Voutp and the drains of the second and third transistors being coupled to the input chopper output Voutn; providing an output chopper; capacitively coupling a differential output Voutp and Voutn of the input chopper to a differential input of the output chopper; wherein providing protection of the gates of the first through fourth transistors from excessive voltages comprises, when a negative common mode voltage surge occurs on the inputs Vinp and Vinn, coupling the gates of the first through fourth transistors to the input Vinp or the input Vinn, which ever is a lower voltage.