Method of and Apparatus for Reducing the Influence of a Common Mode Signal on a Differential Signal and to Systems including such an Apparatus
AssigneeAnalog Devices Global Unlimited Company
InventorsJonathan Ephraim David Hurwitz, George Redfield Spalding, JR., Seyed Amir Ali Danesh
Life of this patent
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Abstract
Differential sampling circuits may be adversely affected by changes in common mode voltage. Changes in the common mode voltage may alter the on resistance of transistor switches which it turn may mean that small signal changes are not correctly observed against a bigger common mode signal. The present disclosure relates to a way of improving the ability to resolve small differential signal changes by varying the supply or drive voltage to a component to compensate for common mode voltage changes.
Claims20
An apparatus comprising an active circuit for adjusting a control voltage of at least one transistor switch or a supply voltage of a differential signal processing circuit as a function of a stimulation signal applied to a first circuit that provides a signal that is switched by the transistor switch or processed by the signal processing circuit.
An apparatus comprising a differential signal processing circuit and a stimulus signal generator, wherein the stimulus signal generator is arranged to apply a stimulus signal to an input circuit that is arranged to supply first and second signals that together form a differential signal to signal inputs of the differential signal processing circuit;
- and wherein the apparatus further comprises a further circuit responsive to the stimulus signal or to a control signal that is correlated with changes in the stimulus signal, and where the further circuit is arranged to cause a change in at least one of:
- a) a control voltage used to control the status of a transistor switch;
- b) a change in a supply voltage of a power supply to at least part of the signal processing circuit;
- and
- c) a change in a reference voltage or signal ground voltage of the signal processing circuit.
A method of improving the common mode rejection ratio of a differential circuit, the method comprising varying first and second supply voltages of the differential circuit as a function of the common mode value of a differential input signal, and/or varying a nominally digital control signal applied to a gate of a field effect transistor acting as a switch or varying a back gate voltage of a field effect transistor acting as a switch as a function of the common mode value of the differential input signal.
Dependencies are inferred from the claim text.