Analog multiplexing

A method for using an input stage for multiplexing, the input stage including an input terminal and an output terminal, the method comprising:

• (a) accepting an voltage input signal at the input terminal of the input stage;
• (b.1) presenting a substantially unmodified version of the voltage input signal at the output terminal of the input stage, when the input stage is selected;
• and
• (b.2) producing a rejection voltage signal of substantially equal magnitude and opposite polarity to the corresponding voltage input signal in order to reject the voltage input signal and thereby present a substantially constant voltage at the output terminal of the input stage regardless of variations in the voltage input signal, when the input stage is deselected.

A method for multiplexing using a plurality of differential amplifiers each including a differential pair of inputs, first and second input stages, a differential pair of transistors, and a differential pair of outputs, the method comprising:

• (a) accepting corresponding first and second voltage input signals at each said differential pair of inputs;
• (b) accepting selection of only one of said plurality of differential amplifiers at a time and deselecting the other differential amplifiers;
• and
• (c) for each differential amplifier
• (c. 1) accepting the corresponding first voltage input signal at an input of the corresponding first input stage and presenting a substantially unmodified version of the corresponding first voltage input signal at an output of the corresponding first input stage when said first differential amplifier is selected, and presenting a substantially constant voltage at the output of the corresponding first input stage when said differential amplifier is deselected, regardless of variations in the corresponding first voltage input signal;
• (c.2) accepting the corresponding second voltage input signal at an input of the corresponding second input stage and presenting a substantially unmodified version of the corresponding second voltage input signal at an output of the corresponding second input stage when said differential amplifier is selected, and presenting a substantially constant voltage at the output of the corresponding second input stage when said differential amplifier is deselected, regardless of variations in the corresponding second voltage input signal;
• (c.3) providing the outputs of the corresponding first and second input stages to control terminals of the corresponding differential pair of transistors;
• (c.4) when the differential amplifier is selected, turning on the corresponding differential pair of transistors so that current mode equivalents of the corresponding first and second voltage input signals are presented at further terminals of the differential pair of transistors, said further terminals forming the corresponding differential pair of outputs of the differential amplifier;
• and
• (c.5) when the differential amplifier is deselected, turning off the corresponding differential pair of transistors so that substantially zero level current outputs are presented at the corresponding differential pair of outputs of the differential amplifier;
• and
• (d) outputting corresponding first and second output signals at each said differential pair of outputs, such that the corresponding first and second output signals of the one differential amplifier selected at one time are current mode equivalents of the corresponding first and second voltage input signals, and the corresponding first and second output signals of the other differential amplifiers are substantially zero level current outputs.