US 7,034,611 B2 · Multistage common mode feedback for improved linearity line drivers

Abstract

A technique to attenuate even-order harmonics of an output stage of a multistage nested Miller compensation circuit. In one example embodiment, this is accomplished by using a low-bandwidth low-swing amplifier in the common mode feedback loop to improve the even-order harmonic performance in the signal path. The technique uses a separate multistage loop for the common mode feedback loop to attenuate the even-order harmonics. The common mode feedback loop is the fourth stage and uses the third stage of the nested Miller compensation circuit. The fourth stage of the common mode feedback loop includes a single harmonic and uses a low voltage supply to achieve lower power consumption by the common mode feedback loop.

Claims20

Dependent claims

A circuit comprising:

a first differential stage having input and output connections;
a second differential stage having input and output connections;
a differential output stage having input and output connections, wherein the second differential stage is connected between the output of the first differential stage and the input of the differential output stage;
a common mode feedback circuit having input and output connections, wherein the differential output stage is connected between the output of the second defferential stage and the input of the common mode feedback circuit, wherein the output of the common mode feedback circuit is connected to the input of the second differential stage;
and
a differential output biasing stage having input and output connections wherein the differential output biasing stage is connected between the output of the second differential stage and the input of the differential output stage.

3 more elements

A differential amplifier circuit comprising:

a first differential amplifier having an input and a plurality of output terminals, wherein the input terminal of the first differential amplifier is to couple to an input signal;
a second differential amplifier having a plurality of input and output terminals, wherein the output terminals of the first stage are coupled to the input terminals of the second stage;
a class AB output stage having a plurality of input and output terminals, wherein the output terminals of the second differential amplifier are coupled to the input terminals of the class AB output stage;
and
a common mode feedback circuit having a plurality of input and output terminals, wherein the output terminals of the class AB output stage are coupled to the input terminals of the common mode feedback circuit, and wherein the output terminals of the common mode feedback circuit are coupled to the input terminals of the class AB output stage, wherein the circuit outputs an amplified signal at the output terminal of the class AB output stage when the input terminals of the first differential amplifier is connected to the input signal.

2 more elements

A multistage amplifier circuit comprising:

a first inverting differential amplifier having an input terminal, to couple to an input signal, and an output terminal;
a non-inverting differential amplifier having an input terminal and an output terminal, wherein the output terminal of the first inverting differential amplifier is connected to the input terminal of the non-inverting differential amplifier;
a second inverting differential amplifier having an input terminal and an output terminal, wherein the output terminal of the non-inverting differential amplifier is connected to the input terminal of the second inverting differential amplifier;
a first outer loop Miller compensation circuit coupled between the output terminal of the second inverting differential amplifier and the input terminal of the non-inverting differential amplifier;
a second outer loop Miller compensation circuit coupled across the input and output terminals of the second inverting differential amplifier;
a common mode differential amplifier having an input terminal and an output terminal, wherein the input terminal to couple to receive a voltage signal;
a third inverting differential amplifier having an input terminal and an output terminal, wherein the output terminal of the common mode differential amplifier is coupled to the input terminal of the third inverting differential amplifier, wherein the output terminal of the third inverting differential amplifier is coupled to the input terminal of the second inverting differential amplifier;
an inner loop common mode feedback circuit coupled across the input terminal and the outer terminal of the second inverting differential amplifier;
and
a compensation circuit coupled across the output terminal of the second inverting differential amplifier and the input terminal of the third inverting differential amplifier.

7 more elements

Dependencies are inferred from the claim text.

Multistage common mode feedback for improved linearity line drivers

Life of this patent

Multistage common mode feedback for improved linearity line drivers

Life of this patent

Abstract

Claims20