Patent ID: 6445331
Filing Date: 2002-09-03
Classification: G06G,H03M

Abstract:
An apparatus for controlling a common-mode input voltage for a differential amplifier, wherein the differential amplifier includes a first input terminal and a second input terminal, the apparatus comprising:a first and second reference capacitance circuit; a first and second input capacitance circuit; a first and second switching circuit that are arranged to initialize the first and second reference capacitance circuits, respectively, to a first potential when the apparatus is in a sample mode; a third and fourth switching circuit that are arranged to initialize the first and second input capacitance circuits, respectively, to a second potential when the apparatus is in the sample mode; a fifth switching circuit that is arranged to couple a first reference signal to the first reference capacitance circuit when the apparatus is in a hold mode; a sixth switching circuit that is arranged to couple a second reference signal to the second reference capacitance circuit when the apparatus is in the hold mode; a seventh switching circuit that is arranged to couple the first reference capacitance circuit and the first input capacitance circuit to the first input of the differential amplifier when the apparatus is in the hold mode; and an eighth switching circuit that is arranged to couple the second reference capacitance circuit and the second input capacitance circuit to the second input of the differential amplifier when the apparatus is in the hold mode, such that the common-mode input voltage of the differential amplifier is determined by at least the first reference signal, the second reference signal, and a third reference signal, wherein the first potential is determined by two of the first, second, and third reference signals, and the second potential is determined by at least one of the first, second, and third reference signals.