Offset correction method and apparatus
AssigneeAnalog Devices, Inc.
InventorKatsufumi Nakamura
Life of this patent
Estimating the term…
Abstract
A method and apparatus for reducing offset errors in a variable gain circuit is offered. A first programmable gain amplifier is located in a feedforward signal path and a second programmable amplifier is connected in feedback with the first programmable gain amplifier. Each programmable gain amplifier has a separate gain control circuit so that the gain of each programmable gain amplifier can be independently controlled.
Claims46
A variable gain circuit comprising:
- a first PGA receiving a first gain control input signal;
- a second PGA, receiving a second gain control input signal, connected in feedback with the first PGA in a feedback loop;
- a first gain control circuit that controls a gain of the first PGA;
- and
- a second gain control circuit that controls a gain of the second PGA dependently from the gain control of the first PGA wherein the feedback loop has a loop gain with a non-zero slope as a function of any of the first and second gain control input signals.
A variable gain circuit comprising:
- a first PGA receiving a first gain control input signal;
- a second PGA, receiving a second gain control input signal, connected in feedback with the first PGA in a feedback loop, wherein the second PGA has an inverse characteristic of the first PGA;
- a first gain control circuit that controls a gain of the first PGA;
- and
- a second gain control circuit that controls the gain of the second PGA independently from the gain control of the first PGA wherein the feedback loop has a loop gain with a non-zero slope as a function of any of the first and second gain control input signals.
A method for reducing offset errors in a variable gain circuit including a first PGA and second PGA connected in feedback in a feedback loop with the first PGA, the method comprising:
- controlling a gain of the first PGA;
- and
- controlling a gain of the second PGA independently from the gain of the first PGA, wherein controlling any of the gain of the first PGA and the gain of the second PGA results in changing a gain of the feedback loop.
A method for reducing offset errors in a variable gain circuit including a first PGA and a second PGA connected in feedback, in a feedback loop, with first PGA, the method comprising:
- controlling a gain of the first PGA using a first gain control circuit;
- and
- controlling a gain of the second PGA independently from the gain control of the first PGA using a second gain control circuit, wherein controlling any of the gain of the first PGA and the gain of the second PGA results in changing a gain of the feedback loop.
Dependencies are inferred from the claim text.