Patent ID: 8184184

Claim:
An analog multiplexer for multiplexing a plurality of input analog signal channels into a single output analog signal channel, the multiplexer comprising: a plurality of input sampling circuits associated with respective ones of the input analog signal channels, the input sampling circuits each comprising positive and negative inputs coupled to respective positive and negative differential signal lines of a corresponding input analog signal channel; and a differential amplifier having positive and negative inputs controllably connectable in turn to each of the input sampling circuits; wherein the analog multiplexer is further configured to connect the positive and negative inputs of a given input sampling circuit to respective first plates of respective first and second sampling capacitors at a predetermined time prior to connecting respective second plates of the first and second sampling capacitors to the respective positive and negative inputs of the differential amplifier; wherein the predetermined time is less than a full clock cycle of a sampling clock of the amplifier; and wherein the given input sampling circuit comprises: a positive signal path having a first switch coupled between the positive input of the input sampling circuit and a first plate of a first sampling capacitor; a negative signal path having a second switch coupled between the negative input of the input sampling circuit and a first plate of a second sampling capacitor; third and fourth switches coupled between respective second plates of the first and second sampling capacitors and a common mode voltage reference; and fifth and sixth switches arranged in series with the respective first and second switches and the respective first and second sampling capacitors in the respective positive and negative signal paths and coupled between the respective second plates of the first and second sampling capacitors and the respective positive and negative inputs of the differential amplifier.