CN102340284B - Low power voltage transconductance adjustable transconductance-constant rail-to-rail input operational amplifier - Google Patents

Abstract

The invention relates to a low-power voltage transconductance adjustable transconductance-constant rail-to-rail input operational amplifier, which comprises a transconductance-constant control circuit, a rail-to-rail input stage and an output stage, wherein the transconductance-constant control circuit makes the transconductance of the rail-to-rail input operational amplifier approximate to twice a reciprocal of a resistance value of a reference resistor by feeding back and controlling the tail current of the rail-to-rail input stage. Simultaneously, the transconductance of the rail-to-rail input operational amplifier can be changed by changing the resistance value of the reference resistor. The rail-to-rail input operational amplifier can work under a low power voltage, and has the advantages of rail-to-rail common mode input range, transconductance adjustability, constant transconductance and the like.

Description

The rail-to-rail input operational amplifier of the constant transconductance that a kind of low supply voltage mutual conductance is adjustable

Technical field

The present invention relates to operational amplifier technical field, relate in particular to a kind of rail-to-rail input operational amplifier of low supply voltage constant transconductance.

Background technology

Operational amplifier is an important module in analog integrated circuit.Along with the high speed development of microelectronics Manufacturing Techniques, the characteristic size of device is more and more less, and the supply voltage can bear is also more and more lower, and this can limit the performance of operational amplifier, such as the common-mode input range of operational amplifier.When operational amplifier is used as buffer, common-mode input range that need to be same large with input reference signal.At this moment just need to use rail-to-rail input operational amplifier to obtain large dynamic range.

Rail-to-rail input operational amplifier is a kind of amplifier of specific type, and its common-mode input voltage range is from negative supply voltage rail to positive voltage rail.Its input stage is inputted inputting forming with a pair of nmos differential by a pair of PMOS difference.When input common mode voltage is near negative supply voltage rail, PMOS difference is inputted conducting, and nmos differential input is to cut-off; When input common mode voltage is near positive voltage rail, the input of PMOS difference is to cut-off, and nmos differential is inputted conducting; When input common mode voltage is in the middle of positive voltage and negative supply voltage, the input of PMOS difference is to inputting all conductings with nmos differential.The problem that rail-to-rail input operational amplifier exists is that its mutual conductance meeting has greatly changed along with the variation of input common mode voltage (in some cases, its mutual conductance changes can reach 100%), and this likely can make circuit vibrate.Mutual conductance feedback is at present for realizing one of the method for the rail-to-rail input operational amplifier of constant transconductance.Existing mutual conductance feedback method is all to adopt a difference input to being used as with reference to mutual conductance, by the nmos differential in input stage, input inputting copying to obtain the mutual conductance of input stage with PMOS difference, by feedback, the two is equated, thereby make the mutual conductance of input stage constant.But in existing circuit implementing method, because the nmos differential of input stage is inputted, to the nmos differential input with copying, to having different input common mode voltages, (the former is rail-to-rail input common mode voltage, and the latter is a fixing input common mode voltage), this makes the two when input common mode voltage is lower, its mutual conductance has larger difference, also require to work under higher supply voltage simultaneously, otherwise can cause mutual conductance in whole common-mode input range to there is larger fluctuation (such as under the working power voltage of 3V, its mutual conductance fluctuation is in 3～4% left and right, and when 1V, its mutual conductance fluctuation is in 11% left and right).

Summary of the invention

Main purpose of the present invention is to overcome the deficiencies in the prior art, and the rail-to-rail input operational amplifier of the adjustable constant transconductance of a kind of low supply voltage mutual conductance is provided.

In order to achieve the above object, technical scheme of the present invention is: the rail-to-rail input operational amplifier (as shown in Figure 1) of the constant transconductance that a kind of low supply voltage mutual conductance is adjustable, is comprised of constant transconductance control circuit (1), rail-to-rail input stage (2) and output stage (3);

The Vinp input of described constant transconductance control circuit (1) is connected with Vinn with outside analog input signal Vinp respectively with Vinn input; Its V _bnoutput and V _bpoutput respectively with the V of described rail-to-rail input stage (2) _bninput and V _bpinput is connected;

The Vinp input of described rail-to-rail input stage (2) is connected with Vinn with outside analog input signal Vinp respectively with Vinn input; Its pOp, pOn, tetra-outputs of nOp and nOn are connected with I_pinp, I_pinn, tetra-inputs of I_ninp and I_ninn of described output stage (3) respectively;

The Output rusults of the vout output output amplifier of described output stage (3).

In the present invention, constant transconductance control circuit (as shown in Figure 2) is by biasing circuit (1.1), and current operator circuit (1.2) and mutual conductance feedback circuit (1.3) form; For generation of output signal V _bpand V _bn, control respectively the input of nmos differential in rail-to-rail input stage (2) to inputting right tail current with PMOS difference, make the mutual conductance of rail-to-rail input stage (2) be approximately 2 times reciprocal of reference resistance resistance.Wherein:

Described biasing circuit (1.1) has 2 outputs, for bias voltage V being provided to the metal-oxide-semiconductor of mutual conductance feedback circuit (1.3) _b3with reference voltage DeltaV; V _b3nMOS pipe M in output and mutual conductance feedback circuit (1.3) ₁₈with NMOS pipe M ₁₉grid be connected; PMOS pipe M in DeltaV output and mutual conductance feedback circuit (1.3) ₇with PMOS pipe M ₁₇grid be connected.

Current operator circuit (1.2) has four outputs, for bias voltage being provided to the metal-oxide-semiconductor of mutual conductance feedback circuit (1.3); V _b4pMOS pipe M in output and mutual conductance feedback circuit (1.3) ₈grid be connected; V _b5nMOS pipe M in output and mutual conductance feedback circuit (1.3) ₁₃grid be connected; V _b6pMOS pipe M in output and mutual conductance feedback circuit (1.3) ₁grid be connected; V _b7nMOS pipe M in output and mutual conductance feedback circuit (1.3) ₂grid be connected; Its function is to make NMOS pipe M ₁₃with PMOS pipe M ₁the electric current flowing through and nmos differential input in rail-to-rail input stage (2) become certain proportionate relationship to the tail current flowing through, and make NMOS pipe M ₂with PMOS pipe M ₈the electric current flowing through and PMOS difference input in rail-to-rail input stage (2) become certain proportionate relationship to the tail current flowing through.

Mutual conductance feedback circuit (1.3) is comprised of 23 metal-oxide-semiconductors and 5 current sources; PMOS manages M ₁drain electrode and current source I ₁one end, NMOS manage M ₂drain electrode, NMOS manage M ₃drain and gate, NMOS manage M ₅grid concurrent; NMOS manages M ₅drain electrode and PMOS pipe M ₄drain and gate, PMOS manage M ₆grid, PMOS manage M ₁₄grid concurrent; PMOS manages M ₆drain electrode and PMOS pipe M ₇source electrode, PMOS manage M ₁₁drain and gate, NMOS manage M ₉drain and gate concurrent; PMOS manages M ₁₄drain electrode and PMOS pipe M ₁₅source electrode, PMOS manage M ₁₂drain and gate, NMOS manage M ₁₀drain and gate concurrent; PMOS manages M ₈drain electrode and PMOS pipe M ₁₁source electrode, PMOS manage M ₁₂source electrode concurrent; NMOS manages M ₁₃drain electrode and NMOS pipe M ₉source electrode, NMOS manage M ₁₀source electrode concurrent; PMOS manages M ₇drain electrode and PMOS pipe M ₁₆drain electrode, NMOS manage M ₂₀drain electrode, NMOS manage M ₁₈source electrode concurrent; PMOS manages M ₁₅drain electrode and PMOS pipe M ₁₇drain electrode, NMOS manage M ₂₁drain electrode, NMOS manage M ₁₉source electrode concurrent; PMOS manages M ₁₅grid and PMOS pipe M ₁₆grid concurrent, and be connected with ground GND; PMOS manages M ₁₆source electrode and reference resistance R ₁one end, current source I ₂one end concurrent; PMOS manages M ₁₇source electrode and reference resistance R ₁the other end, current source I ₃one end concurrent; NMOS manages M ₁₈drain electrode and NMOS pipe M ₂₀grid, NMOS manage M ₂₁grid, current source I ₄one end concurrent; NMOS manages M ₁₉drain electrode and PMOS pipe M ₂₂grid, current source I ₅one end concurrent, and with described output V _bpbe connected; PMOS manages M ₂₂drain electrode and NMOS pipe M ₂₃grid and drain electrode concurrent and with described output V _bnbe connected; PMOS manages M ₁source electrode, PMOS manage M ₄source electrode, PMOS manage M ₆source electrode, PMOS manage M ₁₄source electrode, PMOS manage M ₂₂source electrode, current source I ₁the other end, current source I ₂the other end, current source I ₃the other end, current source I ₄the other end, current source I ₅other end concurrent and with supply voltage V _dDbe connected; NMOS manages M ₂source electrode, NMOS manage M ₃source electrode, NMOS manage M ₅source electrode, NMOS manage M ₂₀source electrode, NMOS manage M ₂₁source electrode, NMOS manage M ₂₃source electrode concurrent and be connected with ground GND.

In the present invention, when the input common mode voltage of rail-to-rail input operational amplifier changes, described constant transconductance control circuit (1), by feedback, is adjusted the nmos differential input of rail-to-rail input stage (2) to inputting right tail current with PMOS difference, makes NMOS pipe M ₉with PMOS pipe M ₁₁the inverse of mutual conductance sum approximate with reference resistance R ₁half of resistance equate.And NMOS pipe M ₉with NMOS pipe M ₁₀, PMOS manages M ₁₁with PMOS pipe M ₁₂respectively that in rail-to-rail input stage (2), nmos differential is inputted inputting right copying with PMOS difference, therefore NMOS pipe M ₉with PMOS pipe M ₁₁mutual conductance sum equate with the mutual conductance of rail-to-rail input stage (2), thereby make rail-to-rail input operational amplifier there is the characteristic of constant transconductance.Meanwhile, change reference resistance R ₁resistance, can change the mutual conductance of rail-to-rail input operational amplifier, thereby realize the adjustable function of mutual conductance.

The rail-to-rail input operational amplifier of the constant transconductance that low supply voltage mutual conductance of the present invention is adjustable has following beneficial effect:

1, the rail-to-rail input operational amplifier that utilizes the present invention to realize, when supply voltage is 1V, when common mode input changes to 1V from 0, its mutual conductance fluctuation can be in 1.2% left and right.Therefore the present invention, when realizing the rail-to-rail input operational amplifier of constant transconductance under low supply voltage, can reach reasonable compromise in power consumption and aspect of performance.

2, utilize the present invention, can change by the resistance of reference resistance in Circuit tuning the mutual conductance of rail-to-rail input operational amplifier, thereby it is adjustable to realize its mutual conductance.

Accompanying drawing explanation

Fig. 1 is the system assumption diagram of the rail-to-rail input operational amplifier of the adjustable constant transconductance of low supply voltage mutual conductance of the present invention

Fig. 2 is the circuit diagram of constant transconductance control circuit of the present invention

Embodiment

Below in conjunction with accompanying drawing, the present invention is described in more detail.

Figure 1 shows that the system assumption diagram of the rail-to-rail input operational amplifier of the constant transconductance that low supply voltage mutual conductance provided by the invention is adjustable, comprise constant transconductance control circuit (1), rail-to-rail input stage (2) and output stage (3).

Fig. 2 is the circuit diagram of constant transconductance control circuit of the present invention.

Biasing circuit (1.1) is used for producing common bank tube M ₁₈and M ₁₉bias voltage.Current source I ₄with current source I ₅as by M ₁₈, M ₁₉, M ₂₀and M ₂₁the active load of the trans-impedance amplifier forming.

Current operator circuit (1.2) is used for producing metal-oxide-semiconductor M ₁, M ₂, M ₈and M ₁₃bias voltage, make to flow through M ₁, M ₂, M ₈and M ₁₃electric current meet formula (1):

$I_{{\mathrm{<figure-callout\; id="1"\; label="M"\; filenames="HSA00000204042700011.png"\; state="\{\{state\}\}">M</figure-callout>}}_1}=0.5*K_1{I}_n,$ $I_{{\mathrm{<figure-callout\; id="2"\; label="M"\; filenames="HSA00000204042700011.png"\; state="\{\{state\}\}">M</figure-callout>}}_2}=0.5*K_1{I}_p,$ $I_{M_8}=I_p,$ $I_{M_{13}}=I_n---\left(1\right)$

I in formula (1) _nand I _pbe respectively the tail current of the NMOS pipe in rail-to-rail input stage (2) and the tail current of PMOS pipe, K ₁for scale factor, its value can equal 1, also can be less than 1.

If current source I ₂and I ₃the electric current flowing through is I, current source I ₁electric current be:

$I_{{\mathrm{<figure-callout\; id="1"\; label="I"\; filenames="HSA00000204042700011.png"\; state="\{\{state\}\}">I</figure-callout>}}_1}=K_{1}I---\left(2\right)$

M ₄pipe, M ₆pipe and M ₁₄the ratio of the breadth length ratio of pipe is: 1: 1/K ₁: 1/K ₁; Like this, flow through M ₄, M ₆pipe and M ₁₄the electric current of pipe is respectively:

$I_{M_4}=K_1(I-0.5I_p+0.5I_n),$ $I_{M_6}=(I-0.5I_p+0.5I_n),$ $I_{M_{14}}=(I-0.5I_p+0.5I_n)---\left(3\right)$

M ₉and M ₁₀pipe has identical breadth length ratio, and the electric current that flows through them is respectively 0.5I _n; M ₁₁and M ₁₂pipe has identical breadth length ratio, and the electric current that flows through them is respectively 0.5I _p; M ₇pipe, M ₁₅pipe, M ₁₆and M ₁₇pipe has identical breadth length ratio.Known according to KCL theorem and formula (1), flow through M ₇pipe, M ₁₅pipe, M ₁₆pipe and M ₁₇the electric current of pipe is (when difference is input as zero):

$I_{M_7}=I_{M_{15}}=I$ $I_{M_{16}}=I_{M_{17}}=I---\left(4\right)$

M ₇pipe, M ₁₅pipe, M ₆pipe, M ₁₄pipe, M ₈pipe, M ₉pipe, M ₁₀pipe, M ₁₃pipe, M ₁₁pipe and M ₁₂pipe forms a trsanscondutance amplifier, and establishing its mutual conductance is Gm1; M ₁₆pipe, M ₁₇pipe, R ₁, I ₂and I ₃another trsanscondutance amplifier forming, establishing its mutual conductance is Gm2.Input at these two trsanscondutance amplifiers adds an identical little differential voltage (DeltaV-0) (wherein DeltaV is produced by biasing circuit (1.1)) respectively, the current change quantity that they is produced separately by negative feedback is equal, that is: Δ i ₁=Gm1*DeltaV=Δ i ₂=Gm2*DeltaV, thus make these two trsanscondutance amplifiers there is identical mutual conductance, i.e. Gm1=Gm2.

Suppose:

gm1 and Gm2 are respectively suc as formula shown in (5) and formula (6):

$\mathrm{<figure-callout\; id="1"\; label="Gm"\; filenames="HSA00000204042700011.png"\; state="\{\{state\}\}">Gm</figure-callout>}1=\mathrm{gm}/(2+\frac{2}{\mathrm{gmn}+\mathrm{gmp}+\mathrm{gdsn}+\mathrm{gdsp}}\mathrm{gm})---\left(5\right)$

Gm2＝gm/(2+R ₁gm) (6)

By formula (5) and formula (6), can be obtained:

$R_1=\frac{2}{\mathrm{gmn}+\mathrm{gmp}+\mathrm{gdsn}+\mathrm{gdsp}}---\left(7\right)$

Due to gdsn, gdsp is conventionally much smaller than gmn, gmp, and formula (7) can be write as:

${\mathrm{<figure-callout\; id="1"\; label="R"\; filenames="HSA00000204042700011.png"\; state="\{\{state\}\}">R</figure-callout>}}_1\&ap;\frac{2}{\mathrm{gmn}+\mathrm{gmp}}---\left(8\right)$

Due to M ₉pipe and M ₁₀pipe and nmos differential in rail-to-rail input stage (2) are inputted identical and have identical tail current, a M ₁₁pipe and M ₁₂pipe and PMOS difference in rail-to-rail input stage (2) are inputted identical and have identical tail current, and the mutual conductance gm_opa of rail-to-rail input stage is:

gm_opa＝gmn+gmp (9)

From formula (8) and formula (9): the mutual conductance of rail-to-rail input stage, i.e. the mutual conductance of rail-to-rail input operational amplifier is:

gm_opa≈2/R ₁ (10)

From formula (10), the mutual conductance of rail-to-rail input stage is approximately reference resistance R ₁2 times reciprocal, if change reference resistance R ₁value, just can change the mutual conductance of rail-to-rail input stage.

It is little that the rail-to-rail input operational amplifier of the constant transconductance that low supply voltage mutual conductance provided by the invention is adjustable has advantages of that working power voltage is low, mutual conductance is fluctuateed.Simulation result shows, when supply voltage is 1V, when common mode input changes to 1V from 0, its mutual conductance fluctuation can be in 1.2% left and right.And can change by the resistance of reference resistance in Circuit tuning the mutual conductance of rail-to-rail input operational amplifier, thereby it is adjustable to realize its mutual conductance.

Claims (1)

1. a rail-to-rail input operational amplifier for the adjustable constant transconductance of low supply voltage mutual conductance, is characterized in that: this circuit is comprised of constant transconductance control circuit (1), rail-to-rail input stage (2) and output stage (3);

The Vinp input of described constant transconductance control circuit (1) is connected with Vinn with outside analog input signal Vinp respectively with Vinn input; Its V _bnoutput and V _bpoutput respectively with the V of described rail-to-rail input stage (2) _bninput and V _bpinput is connected;

The Vinp input of described rail-to-rail input stage (2) is connected with Vinn with outside analog input signal Vinp respectively with Vinn input; Its pOp, pOn, tetra-outputs of nOp and nOn are connected with I_pinp, I_pinn, tetra-inputs of I_ninp and I_ninn of described output stage (3) respectively;

The Output rusults of the vout output output amplifier of described output stage (3);

Described constant transconductance control circuit (1) is by biasing circuit (1.1), and current operator circuit (1.2) and mutual conductance feedback circuit (1.3) form;

The input of described mutual conductance feedback circuit (1.3) is V _b3, V _b4, V _b5, V _b6, V _b7and DeltaV, output is V _bpand V _bn; By 23 metal-oxide-semiconductors, 5 current sources and a resistance form; PMOS manages M ₁drain electrode and current source I ₁one end, NMOS manage M ₂drain electrode, NMOS manage M ₃drain and gate, NMOS manage M ₅grid concurrent; PMOS manages M ₁grid and described input V _b6be connected; NMOS manages M ₂grid and described input V _b7be connected; NMOS manages M ₅drain electrode and PMOS pipe M ₄drain and gate, PMOS manage M ₆grid, PMOS manage M ₁₄grid concurrent; PMOS manages M ₆drain electrode and PMOS pipe M ₇source electrode, PMOS manage M ₁₁drain and gate, NMOS manage M ₉drain and gate concurrent; PMOS manages M ₁₄drain electrode and PMOS pipe M ₁₅source electrode, PMOS manage M ₁₂drain and gate, NMOS manage M ₁₀drain and gate concurrent; PMOS manages M ₈drain electrode and PMOS pipe M ₁₁source electrode, PMOS manage M ₁₂source electrode concurrent; PMOS manages M ₈grid and described input V _b4be connected; PMOS manages M ₈source electrode and supply voltage V _dDbe connected; NMOS manages M ₁₃drain electrode and NMOS pipe M ₉source electrode, NMOS manage M ₁₀source electrode concurrent; NMOS manages M ₁₃grid and described input V _b5be connected; NMOS manages M ₁₃source electrode be connected with ground GND; PMOS manages M ₇drain electrode and PMOS pipe M ₁₆drain electrode, NMOS manage M ₂₀drain electrode, NMOS manage M ₁₈source electrode concurrent; PMOS manages M ₇grid and PMOS pipe M ₁₇grid concurrent, and be connected with described input DeltaV; PMOS manages M ₁₅drain electrode and PMOS pipe M ₁₇drain electrode, NMOS manage M ₂₁drain electrode, NMOS manage M ₁₉source electrode concurrent; PMOS manages M ₁₅grid and PMOS pipe M ₁₆grid concurrent, and be connected with ground GND; PMOS manages M ₁₆source electrode and reference resistance R ₁one end, current source I ₂one end concurrent; PMOS manages M ₁₇source electrode and reference resistance R ₁the other end, current source I ₃one end concurrent; NMOS manages M ₁₈drain electrode and NMOS pipe M ₂₀grid, NMOS manage M ₂₁grid, current source I ₄one end concurrent; NMOS manages M ₁₉drain electrode and PMOS pipe M ₂₂grid, current source I ₅one end concurrent, and with described output V _bpbe connected; NMOS manages M ₁₈grid and NMOS pipe M ₁₉grid concurrent, and with described input V _b3be connected; PMOS manages M ₂₂drain electrode and NMOS pipe M ₂₃grid and drain electrode concurrent and with described output V _bnbe connected; PMOS manages M ₁source electrode, PMOS manage M ₄source electrode, PMOS manage M ₆source electrode, PMOS manage M ₁₄source electrode, PMOS manage M ₂₂source electrode, current source I ₁the other end, current source I ₂the other end, current source I ₃the other end, current source I ₄the other end, current source I ₅other end concurrent and with supply voltage V _dDbe connected; NMOS manages M ₂source electrode, NMOS manage M ₃source electrode, NMOS manage M ₅source electrode, NMOS manage M ₂₀source electrode, NMOS manage M ₂₁source electrode, NMOS manage M ₂₃source electrode concurrent and be connected with ground GND;

Described biasing circuit (1.1) has 2 outputs, for bias voltage V being provided to the metal-oxide-semiconductor of mutual conductance feedback circuit (1.3) _b3with reference voltage DeltaV; V _b3the input V of output and mutual conductance feedback circuit (1.3) _b3be connected; DeltaV output is connected with the input DeltaV of mutual conductance feedback circuit (1.3);

Described current operator circuit (1.2) has four outputs, for bias voltage being provided to the metal-oxide-semiconductor of mutual conductance feedback circuit (1.3); V _b4the input V of output and mutual conductance feedback circuit (1.3) _b4be connected; V _b5input V in output and mutual conductance feedback circuit (1.3) _b5be connected; V _b6input V in output and mutual conductance feedback circuit (1.3) _b6be connected; V _b7input V in output and mutual conductance feedback circuit (1.3) _b7be connected, make the NMOS pipe M in mutual conductance feedback circuit (1.3) ₁₃with PMOS pipe M ₁the electric current flowing through and nmos differential input in rail-to-rail input stage (2) become certain proportionate relationship to the tail current flowing through, and make the NMOS pipe M in mutual conductance feedback circuit (1.3) ₂with PMOS pipe M ₈the electric current flowing through and PMOS difference input in rail-to-rail input stage (2) become certain proportionate relationship to the tail current flowing through;

Described constant transconductance control circuit (1) is for generation of output signal V _bpand V _bn, the nmos differential of controlling respectively in rail-to-rail input stage (2) is inputted inputting right tail current with PMOS difference, makes the mutual conductance of rail-to-rail input stage (2) be approximately the reference resistance R in mutual conductance feedback circuit (1.3) ₁2 times reciprocal of resistance;

When the input common mode voltage of rail-to-rail input operational amplifier changes, described constant transconductance control circuit (1) is by feedback, adjust the nmos differential input of rail-to-rail input stage (2) to inputting right tail current with PMOS difference, make the NMOS pipe M in mutual conductance feedback circuit (1.3) ₉with PMOS pipe M ₁₁the inverse of mutual conductance sum approximate with mutual conductance feedback circuit (1.3) in reference resistance R ₁half of resistance equate; And NMOS in mutual conductance feedback circuit (1.3) pipe M ₉with NMOS pipe M ₁₀, PMOS manages M ₁₁with PMOS pipe M ₁₂respectively that in rail-to-rail input stage (2), nmos differential input, to inputting right copying with PMOS difference, makes the NMOS pipe M in mutual conductance feedback circuit (1.3) ₉with PMOS pipe M ₁₁mutual conductance sum equate with the mutual conductance of rail-to-rail input stage (2), make rail-to-rail input operational amplifier there is the characteristic of constant transconductance; Meanwhile, change the reference resistance R in mutual conductance feedback circuit (1.3) ₁resistance, to change the mutual conductance of rail-to-rail input operational amplifier, realize the adjustable function of mutual conductance.

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