CN101807893A - Large-bandwidth continuous time common-mode feedback circuit and design method thereof - Google Patents

Large-bandwidth continuous time common-mode feedback circuit and design method thereof Download PDF

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Publication number
CN101807893A
CN101807893A CN 201010146364 CN201010146364A CN101807893A CN 101807893 A CN101807893 A CN 101807893A CN 201010146364 CN201010146364 CN 201010146364 CN 201010146364 A CN201010146364 A CN 201010146364A CN 101807893 A CN101807893 A CN 101807893A
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CN
China
Prior art keywords
common
offset
common mode
mode feedback
feedback circuit
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CN 201010146364
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Chinese (zh)
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高静
涂明强
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天津大学
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Priority to CN 201010146364 priority Critical patent/CN101807893A/en
Publication of CN101807893A publication Critical patent/CN101807893A/en

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Abstract

The invention relates to a large-bandwidth continuous-time common-mode feedback circuit and a design method thereof. The method comprises the following steps of: designing an ideal common-mode signal; detecting the common-mode value of an operational amplification output signal through a common-mode detection circuit; comparing the detected common-mode value of the operational amplification output signal with that of the ideal common-mode signal; after amplifying an error signal through the common-mode feedback circuit, outputting two common-mode feedback control signals fed back to the drain electrode of a biasing tube of an operational amplification biasing circuit so that the whole common-mode feedback circuit forms a single-stage amplifier to ensure that the common-mode feedback circuit has enough phase margin; and finally stabilizing the operational-amplified output common-mode point on the ideal common-mode value according to the negative feedback function of common-mode feedback. The invention overcomes the defects that the traditional continuous-time common-mode feedback circuit is a multi-stage amplifier and has poor stability, and ensures that the common-mode feedback circuit is a one-stage common-source cathode-input amplifier through adjusting the feedback point of the common-mode feedback; and the common-mode feedback circuit has favorable stability and is suitable for large-bandwidth ultrahigh-speed full-differential analog circuits.

Description

The method for designing and the circuit thereof of big bandwidth common mode feedback circuit continuous time

Technical field

The present invention relates to a kind of common mode feedback circuit.Particularly relate to a kind of fully differential operational amplifier that is applied to, to satisfy method for designing and the circuit thereof that having of operational amplifier high bandwidth and stability requirement has big bandwidth common mode feedback circuit continuous time of first to the tenth offset.

Background technology

The fully differential circuit is owing to having high output voltage swing and the inhibition of common-mode noises such as power supply being become the common circuit form, the key of fully differential circuit design and difficult point are the designs of common mode feedback circuit, and common mode feedback circuit is the essential part in the fully differential operational amplifier, in high-gain amplifier, the output common mode level is quite responsive to Devices Characteristics and mismatch, and can not reach stable by differential feedback.Therefore, must increase the common mode electrical level that the common-mode feedback network detects two outputs.Common mode feedback circuit generally is divided into two parts: common mode testing circuit and comparison amplifier circuit.Basic principle is to detect output common mode voltage by the common mode testing circuit, input comparison amplifier circuit and preassigned output common mode reference voltage are compared then, their difference are amplified and are turned back to primary circuit the skew of output common mode voltage is proofreaied and correct.If lack good common mode feedback circuit, the output common mode voltage fluctuation can be caused on the one hand, and difference output can be converted into by the asymmetry of circuit, destroy differential output signal; On the other hand, output common mode departs from predetermined value and can cause the difference output voltage swing limited, and then cause and cut the top or cut end distortion, this moment, detected common mode value departed from the common mode value of actual output error, and then return wrong control voltage and further cause common-mode voltage to depart from normal value, have a strong impact on circuit performance.

Common mode feedback circuit can be divided into common mode feedback circuit and switching capacity common mode feedback circuit continuous time usually, wherein:

1, switching capacity common mode feedback circuit:

The switching capacity common mode feedback circuit disperses to the FEEDBACK CONTROL of output common mode voltage, be in half clock cycle that each electric charge shifts, to finish, calibration also is to finish in the half clock cycle that constantly repeats, and switching capacity common mode feedback circuit is as shown in Figure 1 used till today always.

The switching capacity common mode feedback circuit course of work shown in Figure 1 is as follows: in the Ph2 phase, circuit is in the integration phase, switch S 2+, S2-, S4 closure, S1+, S1-, S3 open, common-mode feedback sampling capacitance C3 and C4 preserve the electric charge of reference voltage and bias voltage (Vref-Vbias) decision, output voltage sampling capacitor C1, C2 are connected to the positive-negative output end and the common-mode feedback control end of amplifier, and the voltage on it maintains amplifier output common mode value near the designated value; In the Ph1 phase, the circuit maintenance of sampling, switch S 1+, S1-, S3 closure in the common mode feedback circuit, S2+, S2-, S4 disconnect, and capacitor C 3, C4 and C1, C2 carry out charge distributing, to finish the rectification of an output common mode.Ideally, charge conversion process by many times can make (Vcm-Vsense) to be stabilized in (Vref-Vbias), and (wherein Vcm is output common mode voltage (Voutp-Voutn)/2, Vsense is the common-mode feedback control voltage that is connected to the current source grid in the amplifier, Vref is expectation output common mode reference voltage, and Vbias is the common-mode feedback control reference voltage of expectation).

The switching capacity common mode feedback circuit has been successfully applied in the sampled-data system, especially in the fully differential switched-capacitor circuit.The switching capacity common mode feedback circuit is because can introduce clock coupling and the operating state that disperses makes differential output signal burr occur and is not suitable in circuit continuous time.

2, continuous time common mode feedback circuit

Continuous time, common mode feedback circuit was mainly used in circuit continuous time, and continuous time, common mode feedback circuit carried out continuously to the calibration of output common mode variation.As shown in Figure 2, the circuit working process is as follows: the output common mode level (also can for example utilize the metal-oxide-semiconductor of dark linear zone work to carry out the amplifier common mode electrical level with additive method detects) that detects amplifier by resistance R 1, R1, then detected magnitude of voltage Vcmfb and common mode electrical level Vcm are received on the error amplifier, error is amplified and return control signal as current source grid in the amplifier.Usually, error amplifier is an one-level common source structure for amplifying, and common mode feedback loop has increased the amplification of one-level common source at least again like this, and for the application requirements of big bandwidth, common mode feedback loop is difficult to satisfy the application requirements of enough phase margins.

As shown in Figure 3, in the traditional continuous time common-mode feedback, the feedback point of common-mode feedback is connected on the grid of offset in the amplifier, with the fully differential operational amplifier of traditional common mode feedback circuit, circuit as shown in Figure 4, like this, from input V CmfbArrive amplifier output end vo utn and Voutp with Vcm, be the equal of on the basis of common-mode feedback common-source amplifier, to have increased one-level folded common source and common grid amplifier and the amplification of one-level common source, for big bandwidth amplifier, the phase margin of common mode feedback circuit will be difficult to satisfy.

By feedback point being received the drain electrode of offset in the amplifier, making common mode feedback circuit actual is the one-level cascodes, has greatly increased the stability of common mode feedback circuit.

Summary of the invention

Technical problem to be solved by this invention is, provide a kind of common mode feedback circuit that makes when stablizing the amplifier common-mode point, guarantee the stability of common mode feedback loop, by changing the position of common mode feedback circuit feedback point, making common mode feedback circuit is the cascodes of one-level, make it not need phase compensation and have bigger phase margin, guarantee the method for designing and the circuit thereof of big bandwidth common mode feedback circuit continuous time of its loop stability.

The technical solution adopted in the present invention is: a kind of method for designing of big bandwidth common mode feedback circuit continuous time includes following steps:

1) designs desirable common-mode signal;

2), detect the common mode value of amplifier output signal by the common mode testing circuit;

3) common mode value and the desirable common-mode signal with detected amplifier output signal compares;

4) error signal is amplified by common mode feedback circuit after, export the drain electrode that 2 tunnel common-mode feedback control signals feed back to amplifier biasing circuit offset, make whole common mode feedback circuit form an one-stage amplifier and guarantee that common mode feedback circuit has enough phase margins;

5) according to the negative feedback of common-mode feedback, the output common mode point of amplifier finally is stabilized on the desirable common mode value.

A kind of big bandwidth common mode feedback circuit continuous time that adopts the method for designing design of big bandwidth common mode feedback circuit continuous time, include first to the tenth offset, the described the 7th and the drain electrode of the drain electrode of the grid of the drain electrode of the grid of the 8th offset, the 8th offset, the 9th and the tenth offset, the 9th offset and the second and the 3rd offset all constitute the bias level of common mode feedback circuit to Vbp; The drain electrode of the drain electrode of the 7th offset and the tenth offset and first offset and the 4th offset constitutes the feedback signal of common mode feedback circuit output all to Vsense; The grid of first offset and the 4th offset constitutes the median level of output voltage V outn and Voutp all to Vcmfb; The grid of the second and the 3rd offset all constitutes desirable common mode electrical level value to Vcm; The grid of the 5th and the 6th offset is all to Vbn formation bias level; The source ground of the 5th and the 6th offset, the drain electrode of the 5th offset connects the source electrode of first and second offsets; The drain electrode of the 6th offset connects the source electrode of third and fourth offset.

The method for designing and the circuit thereof of big bandwidth common mode feedback circuit continuous time of the present invention, having overcome traditional continuous time common mode feedback circuit is casacade multi-amplifier, determining of common mode feedback circuit poor stability, by adjusting the feedback point of common-mode feedback, making common mode feedback circuit is the one-level common source and common grid amplifier, common mode feedback circuit has good stable, is applicable to big bandwidth ultrahigh speed fully differential analog circuit.

Description of drawings

Fig. 1 is the switching capacity common mode feedback circuit of prior art;

Fig. 2 is common mode feedback circuit continuous time of prior art;

Fig. 3 is traditional common mode feedback circuit continuous time;

Fig. 4 is the fully differential operational amplifier with traditional common mode feedback circuit;

Fig. 5 is a common mode feedback circuit structure of the present invention;

Fig. 6 is the fully differential operational amplifier with common-mode feedback of the present invention.

Embodiment

Make a detailed description below in conjunction with embodiment and accompanying drawing method for designing and circuit thereof big bandwidth common mode feedback circuit continuous time of the present invention.

The method for designing of big bandwidth common mode feedback circuit continuous time of the present invention includes following steps:

1) designs desirable common-mode signal (Vcm);

2), detect the common mode value (Vcmfb) of amplifier output signal by the common mode testing circuit;

3) the common mode value (Vcmfb) with detected amplifier output signal compares with desirable common-mode signal (Vcm);

4) error signal (Vcmfb-Vcm) is amplified by common mode feedback circuit after, export 2 tunnel common-mode feedback control signals (Vsense1, Vsense2) and feed back to the drain electrode of amplifier biasing circuit offset, make whole common mode feedback circuit form an one-stage amplifier and guarantee that common mode feedback circuit has enough phase margins;

5) according to the negative feedback of common-mode feedback, the output common mode point of amplifier finally is stabilized on the desirable common mode value (Vcm).

As shown in Figure 5, big bandwidth common mode feedback circuit continuous time of the present invention, include first to the tenth offset M1-M10, the drain electrode of the grid of the grid of the described the 7th and the 8th offset M7, M8, the drain electrode of the 8th offset M8, the 9th and the tenth offset M9, M10, the drain electrode of the 9th offset M9 and the second and the 3rd offset M2, M3 all constitutes the bias level of common mode feedback circuit to Vbp; The drain electrode of the drain electrode of the 7th offset M7 and the tenth offset M10 and the first offset M1 and the 4th offset M4 constitutes the feedback signal of common mode feedback circuit output all to Vsense; The grid of the first offset M1 and the 4th offset M4 constitutes the median level of output voltage V outn and Voutp all to Vcmfb; The grid of the second and the 3rd offset M2, M3 all constitutes desirable common mode electrical level value to Vcm; The grid of the 5th and the 6th offset M5, M6 is all to Vbn formation bias level; The source ground of the 5th and the 6th offset M5, M6, the drain electrode of the 5th offset M5 connect the source electrode of the first and second offset M1, M2; The drain electrode of the 6th offset M6 connects the source electrode of the third and fourth offset M3, M4.

Shown in Figure 6 is the fully differential operational amplifier that adopts big bandwidth common mode feedback circuit continuous time of the present invention, is preferred forms of the present invention.Wherein, Vbp, Vbn are bias level, and Vsense is the feedback signal of common mode feedback circuit output, and the grid of offset M1 pipe and offset M4 pipe meets Vcmfb, is the median level of output voltage V outn and Voutp, Vcm is the common mode electrical level value, when the intermediate value voltage deviation common mode electrical level Vcm of output voltage, if V Cmfb＞V CmThe electric current that flows through offset M1 and offset M4 increases, (because offset M7, M8, M9, M10 and offset M5, M6 have bias voltage Vbp fixed bias, therefore the electric current that flows through offset M7, M8, M9, M10 and offset M5, M6 is constant), therefore the electric current in Mp1 and the Mp2 pipe is understood among some offset M1 and offset M4 pipe that flows into the common-mode feedback part in the amplifier, thereby cause amplifier part output level Voutn and Voutp to reduce, vice versa.For the common-mode feedback path, error amplifier is the one-level common-source amplifier, from input V CmfbArriving amplifier output end vo utn and Voutp with Vcm, is the equal of the one-level folded common source and common grid amplifier, and this loop need not compensate and have bigger phase margin.

Claims (2)

1. the method for designing of one kind big bandwidth common mode feedback circuit continuous time is characterized in that, includes following steps:
1) designs desirable common-mode signal (Vcm);
2), detect the common mode value (Vcmfb) of amplifier output signal by the common mode testing circuit;
3) the common mode value (Vcmfb) with detected amplifier output signal compares with desirable common-mode signal (Vcm);
4) error signal (Vcmfb-Vcm) is amplified by common mode feedback circuit after, export 2 tunnel common-mode feedback control signals (Vsense1, Vsense2) and feed back to the drain electrode of amplifier biasing circuit offset, make whole common mode feedback circuit form an one-stage amplifier and guarantee that common mode feedback circuit has enough phase margins;
5) according to the negative feedback of common-mode feedback, the output common mode point of amplifier finally is stabilized on the desirable common mode value (Vcm).
2. big bandwidth common mode feedback circuit continuous time of a method for designing design of adopting described big bandwidth common mode feedback circuit continuous time of claim 1, include first to the tenth offset (M1-M10), it is characterized in that: the drain electrode of the grid of the grid of the described the 7th and the 8th offset (M7, M8), the drain electrode of the 8th offset (M8), the 9th and the tenth offset (M9, M10), the drain electrode of the 9th offset (M9) and the second and the 3rd offset (M2, M3) all constitutes the bias level of common mode feedback circuit to Vbp; The drain electrode of the drain electrode of the 7th offset (M7) and the tenth offset (M10) and first offset (M1) and the 4th offset (M4) constitutes the feedback signal of common mode feedback circuit output all to Vsense; The grid of first offset (M1) and the 4th offset (M4) constitutes the median level of output voltage V outn and Voutp all to Vcmfb; The grid of the second and the 3rd offset (M2, M3) all constitutes desirable common mode electrical level value to Vcm; The grid of the 5th and the 6th offset (M5, M6) is all to Vbn formation bias level; The source ground of the 5th and the 6th offset (M5, M6), the drain electrode of the 5th offset (M5) connects the source electrode of first and second offsets (M1, M2); The drain electrode of the 6th offset (M6) connects the source electrode of third and fourth offset (M3, M4).
CN 201010146364 2010-04-14 2010-04-14 Large-bandwidth continuous time common-mode feedback circuit and design method thereof CN101807893A (en)

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Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102651642A (en) * 2011-02-25 2012-08-29 佳能株式会社 Filter circuit
CN103354443A (en) * 2013-06-20 2013-10-16 华侨大学 CTCMFB (continuous time common-mode feedback) circuit applied to high-speed fully differential operational amplifier
CN103414441A (en) * 2013-08-21 2013-11-27 中国电子科技集团公司第二十四研究所 Open loop amplifier with stable output common-mode voltage
CN103546105A (en) * 2012-07-17 2014-01-29 美国亚德诺半导体公司 Apparatus and methods for amplifier power supply control
CN105391409A (en) * 2015-11-11 2016-03-09 深圳大学 Low-ripple switched-capacitor common-mode feedback structure
CN105634521A (en) * 2014-11-26 2016-06-01 成都振芯科技股份有限公司 MLVDS receiving circuit
CN109546972A (en) * 2019-02-14 2019-03-29 锐迪科微电子（上海）有限公司 Common-mode feedback control circuit and sound output device

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* Cited by examiner, † Cited by third party
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US20040189392A1 (en) * 2003-03-28 2004-09-30 Nec Electronics Corporation Voltage control circuit for common mode voltage and method for controlling the same
US6965268B2 (en) * 2003-08-26 2005-11-15 Intel Corporation Common mode feedback circuit for fully differential two-stage operational amplifiers

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20040189392A1 (en) * 2003-03-28 2004-09-30 Nec Electronics Corporation Voltage control circuit for common mode voltage and method for controlling the same
US6965268B2 (en) * 2003-08-26 2005-11-15 Intel Corporation Common mode feedback circuit for fully differential two-stage operational amplifiers

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102651642A (en) * 2011-02-25 2012-08-29 佳能株式会社 Filter circuit
CN103546105B (en) * 2012-07-17 2016-08-24 美国亚德诺半导体公司 The equipment controlled for APS amplifier power supply and method
CN103546105A (en) * 2012-07-17 2014-01-29 美国亚德诺半导体公司 Apparatus and methods for amplifier power supply control
CN103354443B (en) * 2013-06-20 2016-08-10 华侨大学 It is applied to the continuous time common-mode feedback of high speed Full differential operational amplifier
CN103354443A (en) * 2013-06-20 2013-10-16 华侨大学 CTCMFB (continuous time common-mode feedback) circuit applied to high-speed fully differential operational amplifier
CN103414441A (en) * 2013-08-21 2013-11-27 中国电子科技集团公司第二十四研究所 Open loop amplifier with stable output common-mode voltage
CN105634521A (en) * 2014-11-26 2016-06-01 成都振芯科技股份有限公司 MLVDS receiving circuit
CN105634521B (en) * 2014-11-26 2018-01-23 成都振芯科技股份有限公司 A kind of MLVDS receiving circuits
CN105391409A (en) * 2015-11-11 2016-03-09 深圳大学 Low-ripple switched-capacitor common-mode feedback structure
CN109546972A (en) * 2019-02-14 2019-03-29 锐迪科微电子（上海）有限公司 Common-mode feedback control circuit and sound output device

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Open date: 20100818