Self-regulated reference for switched capacitor circuit

Patent metadata

Field	Value
Publication number	US-9847763-B2
Application number	US-201615166066-A
Country	US
Kind code	B2
Filing date	May 26, 2016
Priority date	Sep 15, 2015
Publication date	Dec 19, 2017
Grant date	Dec 19, 2017

Abstract

A switched-capacitor circuit comprising a differential operational amplifier and a feedback circuit is described. In some embodiments, the feedback circuit may be configured to provide a reference voltage that is insensitive to temperature and/or process variations. In some embodiments, the feedback circuit may be configured to mitigate the time delay associated with one or more capacitors of the switched-capacitor circuit. The switched-capacitor circuit may be controlled by a pair of control signals. During a first phase, one or more capacitors may be charged, or discharged, through an input signal. During a second phase, the electric charge of the one or more capacitors may be retained.

First claim

What is claimed is:

1. A switched-capacitor circuit, comprising:
a differential operational amplifier;
at least one capacitor coupled to an input of the differential operational amplifier; and
a feedback circuit coupled to the input of the differential operational amplifier and an input of the switched-capacitor circuit, the feedback circuit being configured to receive a reference signal and to produce, based at least in part on the reference signal, at least one stabilized reference signal,
wherein the feedback circuit comprises a flipped voltage follower and wherein the flipped voltage follower comprises an input connected to an output of a common source amplifier.

2. The switched capacitor circuit of claim 1 , wherein the feedback circuit comprises a common source amplifier.

3. The switched-capacitor circuit of claim 2 , wherein the common source amplifier exhibits a gain configured to cancel, at least in part, a capacitance of the at least one capacitor.

4. The switched capacitor circuit of claim 2 , wherein the common source amplifier is connected to an active load.

5. The switched capacitor circuit of claim 2 , wherein the common source amplifier comprises a differential amplifier.

6. The switched capacitor circuit of claim 1 , wherein the feedback circuit comprises a replica bias circuit.

7. A switched-capacitor circuit, comprising:
a differential operational amplifier; and
at least one capacitor coupled to an input of the differential operational amplifier; and a feedback circuit coupled to the input of the differential operational amplifier and an input of the switched-capacitor circuit,
wherein the feedback circuit exhibits a gain configured to cancel, at least in part, a capacitance of the at least one capacitor, and
wherein the feedback circuit comprises a flipped voltage follower circuit and wherein the flipped voltage follower comprises an input connected to an output of a common source amplifier.

8. The switched-capacitor circuit of claim 7 , wherein the differential operational amplifier exhibits a feedback factor that is independent of the at least one capacitor.

9. The switched capacitor circuit of claim 7 , wherein the feedback circuit comprises the common source amplifier.

10. The switched capacitor circuit of claim 9 , wherein the common source amplifier is connected to an active load.

11. The switched capacitor circuit of claim 9 , wherein the common source amplifier comprises a differential amplifier.

12. The switched capacitor circuit of claim 7 , wherein the feedback circuit comprises a replica bias circuit.

13. A switched-capacitor circuit, comprising:
a differential operational amplifier;
a first and a second capacitor, the first capacitor being coupled to an input of the differential operational amplifier;
a first feedback circuit coupled to an output of the second capacitor, the input of the differential operational amplifier, and an input of the switched-capacitor circuit, the first feedback circuit being configured to receive a reference signal and to produce, based at least in part on the reference signal, at least one stabilized reference signal; and
a second feedback circuit coupled to an output of the first capacitor and an input of the second capacitor.

14. The switched-capacitor circuit of claim 13 , wherein the first feedback circuit comprises a common source amplifier.

15. The switched-capacitor circuit of claim 13 , wherein the first feedback circuit comprises a flipped voltage follower.

16. A switched-capacitor circuit, comprising:
a differential operational amplifier;
a first and a second capacitor, the first capacitor being coupled to an input of the differential operational amplifier;
a first feedback circuit coupled to an output of the second capacitor, the input of the differential operational amplifier and an input of the switched-capacitor circuit; and
a second feedback circuit coupled to an output of the first capacitor and an input of the second capacitor,
wherein the first feedback circuit exhibits a gain configured to cancel, at least in part, a capacitance of the first capacitor.

17. The switched-capacitor circuit of claim 16 , wherein the first feedback circuit comprises a common source amplifier.

18. The switched-capacitor circuit of claim 16 , wherein the first feedback circuit comprises a flipped voltage follower.

19. The switched capacitor of claim 13 , wherein the first feedback circuit is configured to output a first signal and the second feedback circuit is configured to output a second feedback signal, wherein the first signal and the second signal have opposite phases.

20. The switched capacitor of claim 16 , wherein the first feedback circuit is configured to output a first signal and the second feedback circuit is configured to output a second feedback signal, wherein the first signal and the second signal have opposite phases.

Assignees

• Mediatek Inc

Inventors

• Chang Wen-Hua

Classifications

• H03F1/083 Primary

  in transistor amplifiers (H03F1/10 - H03F1/22 take precedence) · CPC title

• H03F2203/45244

  the differential amplifier contains one or more explicit bias circuits, e.g. to bias the tail current sources, to bias the load transistors · CPC title

• H03F1/30

  Modifications of amplifiers to reduce influence of variations of temperature or supply voltage {or other physical parameters (in differential amplifiers H03F3/45479)} · CPC title

• H03F2200/151

  A source follower being used in a feedback circuit of an amplifier stage · CPC title

• H03F2203/45012

  the addition of two signals being made in a switched capacitor circuit for producing the common mode signal · CPC title