CN101388650A - Nested type Miller active capacitor frequency compensation circuit - Google Patents

Abstract

The invention relates to a nested Miller active capacitance frequency compensating circuit, which is used in a three-level operation amplifier, which is composed of three CMOS amplifier stage circuits, two compensating capacitors, one positive phase current buffer and one reversed phase current buffer which are connected through nestings, wherein a three-level amplifier which is built can be expanded to high frequency on a non-main pole in frequency response characteristics, simultaneously, a zero point of a left half-plane is also introduced, which increases the phase margin and saves the power consumption. Compared with an existing three-level amplifier frequency compensation technique, the frequency compensation technique in the invention realizes high gain and has the advantages of low power consumption, small compensation capacitance, big driving, strong load capacity and the like.

Description

A kind of nested type Miller active capacitor frequency compensation circuit

Technical field

The invention belongs to technical field of integrated circuits, be specifically related to a kind of nested type Miller active capacitor frequency compensation circuit that is used for three-stage operational amplifier.

Background technology

Now, along with the development of integrated circuit technology, the characteristic size of metal-oxide-semiconductor is more and more littler and supply voltage is also more and more lower.In this case, it is no longer suitable to explain in words the cascade technology of system for amplifier.Obtaining high-gain just must the one-stage amplifier of cascade more than three grades or three grades.Have at output under the situation of heavy load electric capacity, develop and both to save area (building-out capacitor is little), consume the three-stage operational amplifier frequency compensation technology of extremely low power dissipation (bias current is little) again, this is people's a research focus [1-3] always.

In general, two big quefrency compensation methodes are arranged, be respectively nested type Miller capacitance compensation (NMC) [4-8] and anti-nested type Miller capacitance compensation (RNMC) [9], both structures as depicted in figs. 1 and 2.Wherein, mutual conductance and capacitive feedback frequency compensation (TCFC) [8] are arranged more typically in the NMC technology, it has been incorporated into an active capacitor in the middle of traditional NMC structure, thereby is able to produce in frequency response raising at the zero point phase margin of a RHP; Anti-active feedback frequency compensation (RAFFC) [9] are more typically arranged in the RNMC technology, and it has been incorporated into an active capacitor in the middle of traditional RNMC structure, is able to produce in frequency response the zero point of a RHP equally.In the middle of the design based on NMC and RNMC, they have all obtained best separately bandwidth power consumption ratio and slew rate power consumption ratio.

Yet all there is certain problem in this two classes circuit.RNMC is that with respect to the advantage of NMC structure it has only a building-out capacitor to load on output.But generally the third level of third stage amplifier always needs the bigger promptly bigger bias current of mutual conductance than preceding two-stage.RNMC has adopted the third level that positive amplifies, and the positive amplification needs the two-way current branch, as shown in Figure 3.This just means that it needs the branch of the bigger electric current of two-way, and this has consumed a lot of power consumptions.On the other hand, be one road current branch (as shown in Figure 4) though the NMC structure only needs the third level of an anti-phase amplification,, its two building-out capacitors all load on the output.Therefore, develop and only to consume half third level electric current of RNMC structure, only have a building-out capacitor to load on the circuit of output again simultaneously, have certain realistic meaning, meet the technical development trend.

List of references

[1]Leung?K?N，Mok?P?K?T.Nested?Miller?compensation?in?low-power?CMOS?design.IEEETrans.Circuits?Syst.II，Analog.Digit.Signal?Process.2001，48(4)，388

[2]Leung?K?N，Mok?P?K?T.Analysis?of?multistage?amplifier-frequency?compensation.IEEETrans.Circuits?Syst.I，Fundam.Theory?Appl.，2001，48(9)：1041

[3]Leung?K?N，Mok?P?K?T，Ki?W?H，et?al.Three-stage?large?capacitive?load?amplifier?withdamping-factor-control?frequency?compensation.IEEE?J.Solid-State?Circuits，2000，35(2)：221

[4]Lee?H，Mok?P?K?T.Active-feedback?frequency-compensation?technique?for?low-powermultistage?amplifiers.IEEE?J.Solid-State?Circuits，2003，38(3)：511

[5]Lee?H，Mok?P?K?T.Advances?in?active-feedback?frequency?compensation?with?poweroptimization?and?transient?improvement.IEEE?Trans.Circuits?Syst.I，2004，51(9)：1690

[6]Lee?H，Leung?K?N，Mok?P?K?T.A?dual-path?bandwidth?extension?amplifier?topology?withdual-loop?parallel?compensation.IEEE?J.Solid-State?Circuits，2003，38(10)：1739

[7]Peng?X，Sansen?W.AC?boosting?compensation?scheme?for?low-power?multistage?amplifiers.IEEE?J.Solid-State?Circuits，2004，39(11)：2074

[8]Peng?X，Sansen?W.Transconductance?with?capacitances?feed-back?compensation?formultistage?amplifiers.IEEE?J.Solid-State?Circuits，2005，40(7)：1515

[9]Grasso?A?D，Palumbo?G，Pennisi?S.Advances?in?reversed?nested?Miller?compensation.IEEE?Trans.Circuits?Syst.I，2007，54(7)：1459

[10]Fan?X，Mishra?C，Sanchez-Sinencio?E.Single?Miller?capacitor?frequency?compensationtechnique?for?low-power?multistage?amplifiers.IEEE?J.Solid-State?Circuits，2003，38(10)：1735

[11]Rincon-Mora?G?A.Active?capacitor?multiplier?in?miller-compensated?circuits.IEEE?J.Solid-State?Circuits，2000，35(1)：26

Summary of the invention

The objective of the invention is to propose a kind of nested type Miller active capacitor frequency compensation circuit that is used for three-stage operational amplifier, overcoming existing shortcoming based on NMC and RNMC technology, thereby realize better bandwidth power consumption than and slew rate power consumption ratio.

To achieve these goals, technology contents of the present invention is: a kind of nested type Miller active capacitor frequency compensation circuit, it is by third stage amplifier (1,2,3), building-out capacitor (4,5), based on the current buffer (6) of positive amplifier, based on current buffer (7) formation of inverting amplifier; Described third stage amplifier (1,2,3) is connected successively, to realize the amplification of signal; The output concurrent of the output of described positive current buffer (6) and negative-phase sequence curent buffer (7) also is connected to the output of amplifier (1); Described building-out capacitor (4) is connected between the input of the output of amplifier (3) and positive current buffer (6), thereby realizes active miller compensation; Described building-out capacitor (5) be connected the output of amplifier (2) and positive current buffer (7) thus input between realize the active miller compensation of nested type.Between the output of the output of amplifier (1) and amplifier (3), be provided with a feedforward transconductance level amplifier gmf, to improve large signal characteristic.

The constructed third stage amplifier non-dominant pole in frequency response characteristic that goes out of nested type Miller active capacitor frequency compensation circuit of the present invention can expand to very high frequency, simultaneously, also introduced the zero point of a left half-plane, this has increased phase margin and has saved power consumption.Therefore the present invention has advantages such as low in energy consumption, that building-out capacitor is little, driving heavy load ability is strong when realizing high-gain.

Description of drawings

Fig. 1 is the structural representation of typical NMC frequency compensation technology;

Fig. 2 is the structural representation of typical R NMC frequency compensation technology;

Fig. 3 is a positive amplifier architecture schematic diagram;

Fig. 4 is the inverting amplifier structural representation;

Fig. 5 is typical current buffer structural representation based on inverting amplifier;

Fig. 6 is based on the current buffer structural representation of positive amplifier;

Fig. 7 is based on the transistor level of the current buffer of positive amplifier and realizes electrical schematic diagram;

Fig. 8 is the structural representation of nested type Miller active capacitor frequency compensation circuit of the present invention;

Fig. 9 is that the transistor level of nested type Miller active capacitor frequency compensation circuit of the present invention is realized schematic diagram.

Label declaration: 1, the progression of the amplifier of 2,3 expression block diagram forms, 4,5,11,12 is building-out capacitor, 6 is the current buffer of positive, 7 is anti-phase current buffer, 8,9,10 be respectively 1,2,3 transistor level and realize, 13 is that the transistor level of the current buffer of positive is realized, 14 be the transistor level realization of anti-phase current buffer.

Concrete implementing measure

Further describe nested type Miller active capacitor frequency compensation circuit of the present invention below in conjunction with accompanying drawing.

Current buffer (Fig. 5) is used to improve performance, for example third stage amplifier [4-6,8,9] and the linear pressurizer of low pressure reduction [11] in a lot of occasions.But generally, an anti-phase amplifier needs.In fact, when the amplifier of a positive existed, we also can construct current buffer, this building method as shown in Figure 6, Fig. 7 is that its transistor level is realized schematic diagram.

Based on the structure of above current buffer, the block diagram of the nested Miller active capacitor compensating circuit of third stage amplifier of the present invention as shown in Figure 8, three amplifiers 1,2,3 are together in series successively, can obtain high-gain thereby constitute three amplifying stages like this.When realizing third stage amplifier frequency compensated, building-out capacitor 4,5 is connected to the output of first order amplifier by the current buffer 6 of positive, anti-phase current buffer 7 respectively, has constituted the nested type Miller active capacitor compensation that the present invention proposes like this.C _P1,2Represent parasitic capacitance at different levels, C _LThen represent load capacitance.In addition, added a feedforward transconductance level amplifier g _MfTo improve large signal characteristic.Suppose gain at different levels much larger than 1, simultaneously C _A,C _B,C _P1And C _P2Much smaller than C _L,The transfer function of system is,

$A\left(s\right)=\frac{A_{\mathrm{dc}}(1+s/{\mathrm{\&omega;}}_2)(1+s/{\mathrm{\&omega;}}_3)}{(1+\frac{s}{p_{-3\mathrm{dB}}})(1+\frac{s}{{\mathrm{\&omega;}}_1}+\frac{{\mathrm{<figure-callout\; id="2"\; label="s"\; filenames="A200810201177E00112.png"\; state="\{\{state\}\}">s</figure-callout>}}^2}{{\mathrm{\&omega;}}_1{\mathrm{\&omega;}}_2})}---\left(1\right)$

Wherein

$A_{\mathrm{dc}}=\frac{g_{m1}{g}_{m2}{g}_{\mathrm{mL}}}{g_{o1}{g}_{o2}{g}_{\mathrm{oL}}}---\left(2\right)$

$p_{-3\mathrm{dB}}=\frac{g_{o1}{g}_{o2}{g}_{\mathrm{oL}}}{k_a{C}_a{g}_{m2}{g}_{\mathrm{mL}}}---\left(3\right)$

${\mathrm{\&omega;}}_1=\frac{k_a{C}_a}{k_b{C}_b}\frac{g_{\mathrm{mL}}}{C_L}---\left(4\right)$

${\mathrm{\&omega;}}_2=\frac{g_{\mathrm{ma}}}{C_a}---\left(5\right)$

${\mathrm{\&omega;}}_3=\frac{g_{\mathrm{mb}}}{C_b}---\left(6\right)$

k _a＝g _maR _a (7)

k _b＝g _mbR _b (8)

Being implemented among Fig. 9 of transistor level of the present invention provides, and two nested Miller active capacitors are by M _B1,2, M _{1A, B}And C _a, C _bRealize; Wherein, the first order 8 is for adopting the amplifying stage of collapsible cascade, and the second level 9 is the positive amplifying stage, and the third level 10 is anti-phase amplifying stage; The transistor level of current buffer realizes that 13,14 is the biasing circuit of the first order, can utilize them to realize positive and anti-phase current buffer simultaneously.Building-out capacitor 11,12 is by current buffer 13,14 nesting formula Miller active capacitor compensating circuits.

The third stage amplifier circuit that constructs like this among the present invention non-dominant pole in frequency response characteristic can expand to very high frequency, shown in (4), (5).Simultaneously, also introduced the zero point of a left half-plane, as the formula (1), this has increased phase margin and has saved power consumption.This class circuit has advantages such as low in energy consumption, that building-out capacitor is little, driving heavy load ability is strong in the realization high-gain, have fabulous application prospect.

Claims (2)

1. nested type Miller active capacitor frequency compensation circuit is characterized in that: it is by third stage amplifier (1,2,3), and building-out capacitor (4,5) based on the current buffer (6) of positive amplifier, constitutes based on the current buffer (7) of inverting amplifier; Described third stage amplifier (1,2,3) is connected successively; The output concurrent of the output of described positive current buffer (6) and negative-phase sequence curent buffer (7) also is connected to the output of amplifier (1); Building-out capacitor (4) is connected between the input of the output of amplifier (3) and positive current buffer (6); Building-out capacitor (5) is connected between the input of the output of amplifier (2) and positive current buffer (7).

2. nested type Miller active capacitor frequency compensation circuit as claimed in claim 1 is characterized in that: be provided with a feedforward transconductance level amplifier g between the output of the output of amplifier (1) and amplifier (3) _Mf

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