Patent attributes
A common mode controller circuit (60) for maintaining a common mode voltage (Vcm) at a first node (52) and a second node (54) in a sample-and-hold circuit receiving a pair of AC coupled differential input signals (Vinp, Vinn) includes first and second resistors (R1/R2) and third and fourth resistors (R3/R4), each set of resistors connected in series between the first and second nodes, and a differential amplifier (A1) having an inverting input terminal coupled to a third node (62) between the first and second resistors, a non-inverting input terminal coupled to a reference voltage (Vref) and an output terminal coupled to a fourth node (64) between the third and fourth resistors. The common mode voltage is sampled at the third node and the differential amplifier provides a sourcing output current indicative of the difference between the sampled common mode voltage and the reference voltage to drive the fourth node.
