Transconductance with capacitances feedback compensation amplifier

Patent metadata

Field	Value
Publication number	US-9941848-B1
Application number	US-201414520060-A
Country	US
Kind code	B1
Filing date	Oct 21, 2014
Priority date	Oct 21, 2014
Publication date	Apr 10, 2018
Grant date	Apr 10, 2018

Abstract

In accordance with embodiments of the present disclosure, a transconductance with capacitances feedback compensation amplifier may include a capacitor in parallel with an inner feedback loop of the amplifier for providing cascade compensation to the amplifier.

First claim

What is claimed is:

1. A transconductance with capacitances feedback compensation amplifier comprising:
a first gain stage having a first gain stage input and a first gain stage output and configured to receive an input signal at the first gain stage input and apply a first gain to the input signal to generate a first gain stage output signal at the first gain stage output;
a second gain stage having a second gain stage input and a second gain stage output and configured to receive the first gain stage output signal at the second gain stage input and apply a second gain to the first gain stage output signal to generate a second gain stage output signal at the second gain stage output;
a third gain stage having a third gain stage input and a third gain stage output and configured to receive the second gain stage output signal at the third gain stage input and apply a third gain to the second gain stage output signal to generate a third gain stage output signal at the third gain stage output, wherein each of the first gain, the second gain, and the third gain comprises a transconductance gain;
an outer feedback loop comprising a first capacitor coupled between the second gain stage input and the third gain stage output;
an inner feedback loop coupled between the third gain stage input and the third gain stage output and configured to provide cascade compensation between the third gain stage input and the third gain stage output; and
a second capacitor in parallel with the inner feedback loop and coupled between the third gain stage input and the third gain stage output.

2. The amplifier of claim 1 , wherein the inner feedback loop comprises:
a third capacitor coupled between the third gain stage output and a feedback gain stage input;
a feedback gain stage having the feedback gain stage input and a feedback gain stage output coupled to the third gain stage input and configured to apply a feedback gain to a signal present at the feedback gain stage input; and
a resistor coupled between the feedback gain stage input and ground.

3. The amplifier of claim 2 , wherein the feedback gain is a transconductance gain, wherein the resistor has a resistance equal to an inverse of a gain of the feedback gain.

4. The amplifier of claim 1 , wherein the first gain and the second gain are each a non-inverting gain and the third gain is an inverting gain.

5. An integrated circuit comprising:
a first path portion comprising a transconductance with capacitances feedback compensation amplifier having:
a first gain stage having a first gain stage input and a first gain stage output and configured to receive an analog input signal at the first gain stage input and apply a first gain to the input signal to generate a first gain stage output signal at the first gain stage output;
a second gain stage having a second gain stage input and a second gain stage output and configured to receive the first gain stage output signal at the second gain stage input and apply a second gain to the first gain stage output signal to generate a second gain stage output signal at the second gain stage output;
a third gain stage having a third gain stage input and a third gain stage output and configured to receive the second gain stage output signal at the third gain stage input and apply a third gain to the second gain stage output signal to generate an output signal at the third gain stage output, wherein each of the first gain, the second gain, and the third gain comprises a transconductance gain;
an outer feedback loop comprising a first capacitor coupled between the second gain stage input and the third gain stage output;
an inner feedback loop coupled between the third gain stage input and the third gain stage output and configured to provide cascade compensation between the third gain stage input and the third gain stage output; and
a second capacitor in parallel with the inner feedback loop and coupled between the third gain stage input and the third gain stage output; and

a second path portion configured to convert a digital input signal into the analog input signal.

6. The integrated circuit of claim 5 , wherein the inner feedback loop comprises:
a third capacitor coupled between the third gain stage output and a feedback gain stage input;
a feedback gain stage having the feedback gain stage input and a feedback gain stage output coupled to the third gain stage input and configured to apply a feedback gain to a signal present at the feedback gain stage input; and
a resistor coupled between the feedback gain stage input and ground.

7. The integrated circuit of claim 6 , wherein the feedback gain is a transconductance gain, wherein the resistor has a resistance equal to an inverse of a gain of the feedback gain.

8. The integrated circuit of claim 5 , wherein the first gain and the second gain are each a non-inverting gain and the third gain is an inverting gain.

9. A personal audio device comprising:
an audio transducer configured to generate sound in accordance with an output signal received by the audio transducer;
a signal path coupled to the audio transducer, wherein the signal path comprises:
a first path portion comprising a transconductance with capacitances feedback compensation amplifier having:
a first gain stage having a first gain stage input and a first gain stage output and configured to receive an analog input signal at the first gain stage input and apply a first gain to the input signal to generate a first gain stage output signal at the first gain stage output;
a second gain stage having a second gain stage input and a second gain stage output and configured to receive the first gain stage output signal at the second gain stage input and apply a second gain to the first gain stage output signal to generate a second gain stage output signal at the second gain stage output;
a third gain stage having a third gain stage input and a third gain stage output and configured to receive the second gain stage output signal at the third gain stage input and apply a third gain to the second gain stage output signal to generate the output signal at the third gain stage output, wherein each of the first gain, the second gain, and the third gain comprises a transconductance gain;
an outer feedback loop comprising a first capacitor coupled between the second gain stage input and the third gain stage output;
an inner feedback loop coupled between the third gain stage input and the third gain stage output and configured to provide cascade compensation between the third gain stage input and the third gain stage output; and
a second capacitor in parallel with the inner feedback loop and coupled between the third gain stage input and the third gain stage output; and

a second path portion configured to convert a digital input signal into the analog input signal.

10. The personal audio device of claim 9 , wherein the inner feedback loop comprises:
a third capacitor coupled between the third gain stage output and a feedback gain stage input;
a feedback gain stage having the feedback gain stage input and a feedback gain stage output coupled to the third gain stage input and configured to apply a feedback gain to a signal present at the feedback gain stage input; and
a resistor coupled between the feedback gain stage input and ground.

11. The personal audio device of claim 10 , wherein the feedback gain is a transconductance gain, wherein the resistor has a resistance equal to an inverse of a gain of the feedback gain.

12. The personal audio device of claim 9 , wherein the first gain and the second gain are each a non-inverting gain and the third gain is an inverting gain.

Assignees

• Cirrus Logic Inc

Inventors

• Zanbaghi Ramin
• Brennan Aaron
• Gaboriau Johann
• Drakshapalli Prashanth
• Parupalli Vamsikrishna

Classifications

• H03F2200/54

  Two or more capacitor coupled amplifier stages in cascade · CPC title

• H03F3/187 Primary

  in integrated circuits · CPC title

• H03F2200/03

  the amplifier being designed for audio applications · CPC title

• H03F1/02

  Modifications of amplifiers to raise the efficiency, e.g. gliding Class A stages, use of an auxiliary oscillation · CPC title

• H03F2200/408

  the output amplifying stage of an amplifier comprising three power stages · CPC title