Back to results
US 2004/0056718 A1Published application
DC-compensation loop for variable gain amplifier
AssigneeTelefonaktiebolaget LM Ericsson (publ)
InventorLars Nicklasson
Life of this patent
Estimating the term…
Abstract
An apparatus consisting of a variable gain amplifier having an input and an output having a DC-offset compensation loop connected between the output and the input of the variable gain amplifier. The DC-offset compensation loop having a gain independent cutoff frequency.
Claims6
An apparatus, comprising:
- a variable gain amplifier having an input and an output;
- a DC-offset compensation loop connected between the output and the input of the variable gain amplifier, said DC-offset compensation loop having a gain independent cut off frequency;
- and
- wherein the variable gain amplifier and the DC-offset compensation loop are controlled responsive to a same digital code word input.
1 more element
An apparatus, comprising:
- a variable gain amplifier responsive to a digital word input for controlling a gain of the variable gain amplifier having an input and an output;
- a programmable current source responsive to the digital word input for generating a bias current;
- a first transconductance amplifier for generating an error current responsive to an output voltage of the variable gain amplifier and the bias current of the programmable current source;
- a capacitor for integrating the error current and providing an integrated capacitor voltage;
- a second transconductance amplifier for generating an offset canceling current pair responsive to a difference between the integrated capacitor voltage and a reference voltage;
- and
- an input transconductance amplifier connected to the input of the variable gain amplifier for generating a DC-offset canceling voltage responsive to the offset canceling current pair and an input signal, wherein the input transconductance amplifier further comprises a pair of drain resistors connected to receive the offset canceling current pair.
4 more elements
A method for DC-offset compensation with a variable gain amplifier, comprising the steps of
- sensing a difference in output voltage at outputs of the variable gain amplifier,
- generating an error current responsive to the difference in the output voltage and a bias current, wherein the bias current is controlled by a digital control word that also controls a gain of the variable gain amplifier;
- integrating the error current and producing an integrated voltage;
- determining a difference between the integrated voltage and a reference voltage;
- generating an offset canceling current pair responsive to the determined difference and an input signal;
- and
- generating a DC-offset canceling voltage signal at the input of the variable gain amplifier responsive to the offset canceling current pair.
4 more elements
Dependencies are inferred from the claim text.