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 International Unlimited Company
InventorsJonathan Ephraim David Hurwitz, George Redfield Spalding, Jr., Seyed Amir Ali Danesh
Life of this patent
Estimating the term…
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.
Claims26
An apparatus comprising:
- an active circuit that is configured to:
- determine an adjustment to a control voltage of a differential signal processing circuit by using an indication of a time varying perturbation of a common mode voltage of a differential pair of signals determined by a first circuit and, processed by the differential signal processing circuit to estimate the common mode voltage generated using the differential pair of signals;
- and
- adjust the control voltage of the differential signal processing circuit based on a stimulation signal being applied to the first circuit.
An apparatus comprising:
- a differential signal processing circuit and a stimulus signal generator, wherein the stimulus signal generator is arranged to apply a stimulation 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;
- a correction signal generator circuit to receive the stimulation signal and generate a correction signal based on an estimated change in a common mode voltage developed between the inputs of the differential signal processing circuit responsive to the stimulation signal, the correction signal generator circuit configured to determine the estimated change using an indication of a time varying perturbation of a common mode voltage in the stimulation signal;
- and
- a further circuit that is configured to adjust a resistance of a transistor switch of the differential signal processing circuit to offset a change in the resistance of the transistor switch caused by the stimulation signal.
A method of improving a common mode rejection ratio of a differential circuit, the method comprising:
- generating a correction signal based on an estimated change in a common mode voltage of a pair of differential input signals of a differential circuit responsive to a stimulation signal;
- and
- adjusting operation of a field effect transistor responsive to the correction signal, the field effect transistor being configured as a switch for sampling an input of the differential circuit.
Dependencies are inferred from the claim text.