Differential current source with active common mode reduction
AssigneeLake Shore Cryotronics, Inc.
InventorGeoffrey S. Pomeroy
Life of this patent
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Abstract
A voltage-controlled current source provides operation as either a differential current source for a floating load, or operation as a grounded current source when one end of the load is grounded. Switching between operation as a differential current source and operation as a grounded current source is automatic, and will accommodate significant lead resistance between the source and the load. Additionally, in absence of a grounded load the circuit can provide active common mode reduction using active feedback to reduce common mode voltage on the load.
Claims6
A voltage controlled current source for producing a desired load current which flows through a selected load impedance, the load current being a function of provided input voltage and being substantially independent of the load impedance;
- wherein the voltage controlled current source can operate as a differential current source for a floating load or as a grounded load current source when one end of the load is grounded;
- and wherein the voltage controlled current source comprises:
- a) two symmetrical halves that drive each end of the load;
- b) a means of centering an operating voltage between power supply rails;
- and
- c) a means of minimizing average DC voltage of an AC current source without manual adjustment.
A voltage controlled current source for producing a desired load current which flows through a selected load impedance, the load current being a function of provided input voltage and being substantially independent of the load impedance;
- wherein the voltage controlled current source can operate as a differential current source for a floating load or as a grounded load current source when one end of the load is grounded;
- and wherein the voltage controlled current source comprises:
- a) two symmetrical halves that drive each end of the load;
- b) a means of centering an operating voltage between power supply rails;
- c) a means of minimizing average DC voltage of an AC current source without manual adjustment;
- d) a plurality of sense resistors and switching means in providing a range switching feature;
- and
- e) active common mode reduction.
Dependencies are inferred from the claim text.