Patent ID: 7786767

Claim:
An apparatus for rejecting common-mode input voltage variations in a differential sampler, comprising: a first sampler, for sampling a first differential input voltage, Vinp, at a given time, the first differential input voltage having a first common mode component; a second sampler, for sampling a second differential input voltage, Vinm, at the given time, the second differential input voltage having a second common mode component; a circuit for sensing common-mode variations in the first and second differential input voltages, the circuit detecting such common-mode variations as a corresponding common mode voltage Vcmi; a third sampler, for sampling the common mode voltage, Vcmi, at the given time; a discharge path connected to the first and second sampler and also connected to a common discharge node, Vdch, to provide a common path for discharging sampled current for each of the first and second samplers; and a fixed voltage source, for maintaining the discharge node, Vdch, at a substantially constant voltage difference with respect to the common mode voltage, Vcmi.