Multiplexed signal reference level equalizer

Abstract

A multiplexed signal reference level equalizer is arranged to provide an output signal which is a function of different selectable input signals wherein the input signals have respective reference, or common, signal levels. An input signal multiplexer is used to select an input signal from a plurality of remote variable signals or known local calibration signals. The selected remote signal has a common mode signal, represented by the difference between the remote signal common and a local common, superimposed on it. The combined signal is applied to the non-inverting input of a first operational amplifier. Concurrently, the common mode signal is amplified by a second operational amplifier and is applied to the inverting input of the first operational amplifier to be subtracted from the combined signal. A selected local input signal has the common mode signal superimposed on it before it is applied to the first operational amplifier for a similar common mode signal subtraction process. In this way, the equalizer circuit treats the selected local calibration signals in the same manner as a selected remote signal. By setting the various resistors in the circuit to predetermined resistance values, the relationship of the equalizing circuit output signal to its input signal is arranged to be 1.5 times the input signal selected by the multiplexer even though the input signals have different reference signal levels.

Dependencies are inferred from the claim text.