Back to results
US 5,933,056 AGranted
Single pole current mode common-mode feedback circuit
AssigneeExar Corporation
InventorBret C. Rothenberg
Life of this patent
Estimating the term…
Abstract
A CMFB circuit that contains only one voltage amplifier in the loop, and is therefore immune to multi-pole stability problems. This is accomplished by providing feedback in the form of current which sums with a constant node current of the differential voltage amplifier. This control current source is created with two transistors, one controlled by the desired, common-mode voltage level, and another connected to the actual, measured common-mode output level.
Claims11
A common-mode voltage amplifier loop comprising:
- a differential amplifier containing a common-mode control node, said differential amplifier including
- an amplifier positive input transistor,
- an amplifier negative input transistor, a first current source coupled to said input transistors, and a current input to control a common-mode output level;
- a common-mode measuring circuit;
- and a common-mode control circuit, coupled between said common-mode measuring circuit and said common-mode control node;
- for providing a common-mode control current to said common-mode control node.
3 more elements
A common-mode voltage amplifier loop comprising:
- a differential amplifier containing a common-mode control node;
- a common-mode measuring circuit comprising a resistor interpolator;
- and a common-mode control circuit coupled between said common-mode measuring circuit and said common-mode control node, for providing a common-mode control current to said common-mode control node.
A differential voltage amplifier comprising:
- a voltage supply;
- a differential amplifier positive input transistor;
- a differential amplifier negative input transistor;
- a first constant current source coupled to said input transistors;
- a common-mode measuring circuit coupled between a positive and negative output of said voltage amplifier;
- a second, common-mode constant current source coupled to said voltage supply;
- a first common-mode control transistor coupled to said second, common-mode constant current source and having a control input coupled to a desired common-mode voltage reference;
- and
- a second common-mode control transistor having a first node coupled to said second, common-mode constant current source and having a control input coupled to a common-mode output of said common-mode measuring circuit, and having a second node coupled to a current input control node between said first constant current source and said differential amplifier input transistors for setting a common-mode output voltage of the differential amplifier to a control voltage applied as the desired common-mode reference.
6 more elements
Dependencies are inferred from the claim text.