CN100527609C - Variable gain amplifying circuit and relative method - Google Patents
Variable gain amplifying circuit and relative method Download PDFInfo
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- CN100527609C CN100527609C CNB2005101181630A CN200510118163A CN100527609C CN 100527609 C CN100527609 C CN 100527609C CN B2005101181630 A CNB2005101181630 A CN B2005101181630A CN 200510118163 A CN200510118163 A CN 200510118163A CN 100527609 C CN100527609 C CN 100527609C
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Abstract
This invention provides a variable gain amplifying circuit and its related method, which provides a variable reference current according to the value of a control-signal, then divides the reference current into a load current and an input control current based on the differential drive between the control-signal and the constant value reference signal to bias the input circuit and the load circuit of the amplifier to control the gain with the ratio between the two currents, therefore, the control signal value can be used to regulate the gain.
Description
Technical field
The present invention provides a kind of variable-gain amplification circuit and related methods, refer to especially a kind of at the bias voltage amplifier input stage and can strengthen variable-gain amplification circuit and the correlation technique of bias voltage difference during active load to realize preferable variable gain characteristic.
Background technology
In modern information-intensive society, various files, data, data and audio and video information can both be exchanged in the mode of electronic signal, handle, transmit.Therefore, be used for handling the various signal processing circuits of electronic signal, also just become one of most important hardware foundation of advanced information society.
And even in many communications, medium/electronic signaling systems such as transmission broadcast medical image, suitably keeping the signal magnitude amplitude is one of key of signal processing, and variable-gain amplification circuit also just arises at the historic moment.Variable-gain amplification circuit can be exported input signal gain back originally as an amplifier, and its gain size then can be controlled by another control signal (for example being to control voltage).Utilize variable-gain amplification circuit, just can carry out suitable adjustment to the magnitude of size of signal, for example be to form an automatic gain control circuit (AGC, Automobile-Gain Control), with the magnitude of size of conditioning signal automatically with variable-gain amplification circuit.
Since the gain of variable-gain amplification circuit can be controlled by the value of control signal, the situation that its gain changes with control signal is the variable gain characteristic of this variable-gain amplification circuit.In general, when design/manufacturing variable-gain amplification circuit, can wish that all its variable gain characteristic has the gain ranging of broad, preferable controlled characteristic (similarly being to have high linear degree) also will be arranged, and can suitably resist the characteristic drift that the variation of processing procedure or operating temperature is caused.Wherein, gain ranging is meant the scope of gain-variable, just the scope between least gain and maximum gain in the variable gain.In same control signal excursion, if degree and scope that gain-variable moves are big more, gain ranging is also just big more.Variable-gain amplification circuit with higher gain scope can change its gain significantly, so can adapt to the signal of more kinds of different amplitudes, has higher using value.As for the controlled characteristic of variable gain, then Available Gain is represented with the indicatrix that control signal changes.This indicatrix can meet certain default specific curves (for example being the straight line of approaching more linearity) more, just represents the situation of its change in gain to be controlled more explicitly, also just can realize out preferable variable gain characteristic.In addition, just as all electronic circuits, the ambient temperature of process variation and circuit running also can change the characteristic of each circuit element in the variable-gain amplification circuit, and it is floated from original design load.Therefore, the variable-gain amplification circuit practical manifestation variable gain characteristic of coming out also may be subjected to the influence of processing procedure, these undesirable factors of temperature and not as original expection.Preferable variable-gain amplification circuit should suitably be resisted processing procedure, characteristic drift that temperature caused, and its variable gain characteristic can not changed significantly because of these undesirable factors.
Yet in known various variable-gain amplification circuits, Chang Wufa takes above-mentioned all considerations fully into account.For example, some known variable gain amplifying technique has preferable controlled characteristic, undesirable factors such as processing procedure, temperature also had to a certain degree resistivity, but its gain ranging is less, often to be connected in series (cascade) a plurality of identical variable-gain amplification circuits and could realize out bigger gain ranging, will take more layout area and be connected in series a plurality of variable-gain amplification circuits, power consumption also can be bigger, frequency range that also can the shrinkage limit amplifying signal.In addition, also have some known variable gain amplifying techniques can realize out the gain ranging of broad, but its resistivity to undesirable factor is relatively poor, makes its variable gain characteristic be easier to float from former design load because of factors such as process temperatures.
Summary of the invention
Therefore, purpose of the present invention promptly is to propose a kind of variable-gain amplification circuit and correlation technique with novelty, to realize out having broad gain ranging, preferable controlled characteristic, and can suitably resist the variable-gain amplification circuit of undesirable factor, to overcome the shortcoming of prior art.
Variable-gain amplification circuit of the present invention mainly can be provided with gain control circuit and gain unit, is output signal so that input signal is gained, and makes gain can be controlled by control signal.Can be provided with variable current circuit and differential current circuit in the gain control circuit.Variable current circuit can provide the corresponding reference electric current according to control signal, makes the value of the size of current of this reference current corresponding to control signal.The differential current circuit then can be according to control signal and reference current is split into load current and input Control current, makes load current and imports the value that current difference between Control current is controlled by this control signal.Owing to this load current and input Control current are to be gone out by reference current shunting, thus load current and input Control current with also just be equivalent to reference current.
As for gain unit, then can include load circuit and input circuit (and other relevant auxiliary circuit).Wherein, load circuit is used to provide active load.This load circuit can come bias voltage according to load current, makes the equivalent load value of active load can be controlled by the size of load current.Input circuit then is used for receiving the input signal of variable-gain amplification circuit, and power conversions can be provided (similarly is transduction, transconductance) input signal is converted to corresponding electric power (similarly be with voltage form input signal be converted to electric current).This electric power is injected into load circuit, just can set up output signal on load circuit, as the output of variable-gain amplification circuit.Be similar to the bias relation between load current and the load circuit, this input circuit then can give bias voltage according to the input Control current, makes the power conversions degree (similarly being the value of transduction) of input circuit can be controlled by the size of current of importing Control current.
By above-mentioned gain unit configuration as can be known, the power conversions degree of input circuit and the active load that load circuit is provided are just depended in the gain of variable-gain amplification circuit of the present invention.If realize input circuit and load circuit with metal oxide semiconductor transistor, then the power conversions degree of input circuit (similarly being the transduction value) can depend on input Control current size, and the resistive equivalent load value that load circuit provides then is relevant to the inverse of load current value.Therefore, the gain between input signal and output signal will be controlled by the ratio of input Control current to load current.If the input Control current changes to some extent to the ratio of load current, gain also will relatedly change.Because the size of current of load current and input Control current all is controlled by the value of control signal in gain control circuit, also therefore, the value of control signal can change load current and the value of importing Control current, changes gain jointly, to realize out variable gain.
By above-mentioned discussion as can be known, in certain control signal excursion (just when the value of control signal changes within the specific limits), if can make the mutual degree of variation between input Control current and load current big more, the intensity of variation of gain also will become greatly thereupon, and then realizes out the gain ranging of broad.And in the gain control circuit of variable-gain amplification circuit of the present invention, not only can in the differential current circuit, make the difference of input Control current and load current be controlled by control signal, also additionally utilized variable current circuit and make this two electric current and (being reference current) also be controlled by control signal, so just can strengthen the mutual difference degree between input Control current and load current, make variable-gain amplification circuit of the present invention have the gain ranging of broad.In one embodiment of this invention, the function that a pair of p type of available complementation and n-type metal oxide semiconductor transistor realize variable current circuit, control signal can be distinguished the conducting electric current on the two transistor of this a pair of complementary structure, and totalling becomes reference current.
In one embodiment of the invention, drive out input Control current and load current respectively in can in the differential current circuit of gain control circuit, coming differentially by reference current with two homotype metal oxide semiconductor transistors (two p type metal oxide semiconductor transistors for example).Because the circuit of differential driving has preferable resistance to undesirable factors such as temperature, process variation, jointly, the variable gain characteristic of variable-gain amplification circuit of the present invention also can preferably be resisted these undesirable factors.In the differential current circuit, shunt the controlled characteristic that also can make variable-gain amplification circuit of the present invention have preferable (comparatively linearity) with differential driving.
Technical spirit of the present invention can be widely used in the variable-gain amplification circuit that variable-gain amplification circuit that single-ended output goes into or differential output are gone into.If will be used for realizing the variable-gain amplification circuit that differential output is gone into, the common mode feedback circuit of also can arranging in pairs or groups in addition in the variable-gain amplification circuit of the present invention is adjusted common mode (common mode) level in the differential output signal.
Description of drawings
The 1st figure is the desirable variable gain characteristic of a variable-gain amplification circuit.
The 2nd figure, the 3rd figure are respectively two kinds of different known variable gain amplifying circuits.
The 4th figure is the function block schematic diagram of variable-gain amplification circuit of the present invention.
The 5th figure is a kind of embodiment of amplifying circuit among the 4th figure.
The 6th figure is a kind of embodiment of variable current circuit among the 5th figure.
The 7th figure is the situation that each correlation properties is controlled by control signal in the 6th figure amplifying circuit.
[main element label declaration]
10,20,30 amplifying circuits, 12,22,32 gain units
14,24,34 common mode feedback circuits
16,26,36 gain control circuits
18,19a-19b, 28a-28b, 29a-29b, 39a-39b current source
38 variable current circuit, 40 differential current circuit
42 auxiliary circuits, 50 input circuits
52 load circuit Vdd, G direct voltage
Io, It0, Ii0, Ip0, In0, It, Ii, Ir, IiT, ItT, Ip, In electric current
T1-T20, Q1-Q18, M1-M26 transistor
Vref, Vcm voltage
Vi+, Vi-, Vo+, Vo-signal Cc electric capacity
Vc control signal Ns node
Embodiment
Please refer to the 1st figure, what it was illustrated is the desirable variable gain characteristic of variable-gain amplification circuit, and its transverse axis is the value of control signal, and the longitudinal axis is the gain (with decibel represent) of output signal to input signal.Just indicate as the 1st figure, the scope of change in gain is gain ranging in the control signal excursion.If the may command gain changes more significantly in fixing control signal excursion, just can realize out the gain ranging of broad.In addition, shown in the 1st figure, desirable variable gain characteristic can have linear controlled characteristic between controlled signal and gain, that is to say control signal and the corresponding indicatrix that is rendered as skew lines that closes that gains between the decibel value.Therefore, if the slope of this linear controlled characteristic is increased, just can go out broad, bigger gain ranging at the control signal excursion intramedullary expansion of fixing.
Please refer to the 2nd figure, it is the variable-gain amplification circuit 10 (hereinafter to be referred as amplifying circuit 10) of traditional design, its design concept can be with reference to P.Huang, " A 3.3-VCMOS Wideband Exponential Control Variable-Gain-Amplifier " (the inter.Sym.On Cir.and Sys., May 1998) of L.Y Chiou and C.K.Wang.The variable-gain amplification circuit that amplifying circuit 10 is gone into for differential output, voltage signal Vi+, Vi-are differential input signal, and voltage signal Vo+, Vo-just are the differential output signal after the gain, and voltage signal Vc then is the control signal of ride gain.Amplifying circuit 10 is biased between direct voltage Vdd and the G (for example being the ground terminal voltage), can be provided with gain unit (gaincell) 12, common-mode feedback (common-mode feed back) circuit 14 and gain control circuit 16 in it.Be provided with constant current source 18 in the gain control circuit 16 and be used to provide definite value direct current Io, and the p type metal oxide semiconductor transistor Q15 that links to each other with two source electrodes, that Q16 forms differential driving is right.The grid of this two transistor Q15, Q16 just is controlled by control signal Vc and definite value direct voltage Vref respectively, so that the electric current I o on the common source is split into electric current I t0 and Ii0 respectively, just makes Io=It0+Ii0.And the n-type metal oxide semiconductor transistor Q18 in gain control circuit 16 just can form current mirror with the corresponding transistor Q2 in the gain unit 12, with electric current I t0 Mirroring Mapping to transistor Q2.In like manner, the n-type metal oxide semiconductor transistor Q17 in the gain control circuit 16 can form another current mirror with the corresponding transistor Q1 in the gain unit 12, with electric current I i0 Mirroring Mapping to transistor Q1.
In gain unit 12, it then is n-type metal oxide semiconductor transistor Q3, Q4 formation input stage (input stage) with two couplings, and n-type metal oxide semiconductor transistor Q5, the Q6 of two couplings just can provide active load to this input stage in addition, and p type metal oxide semiconductor transistor Q7, the Q8 of two couplings then can be as the bias voltage auxiliary circuit of input stage and active load.In input stage, the grid of two transistor Q3, Q4 is used for receiving inputted signal Vi+ and Vi-respectively, and, because these two transistor Q3, Q4 are connected in transistor Q1 via common source electrode, so two transistorized operation situations will be controlled by the bias voltage of electric current I i0.In active load, the drain electrode of two transistor Q5, Q6 then is used for output signal Vo+ and Vo-respectively, similarly, because these two transistor Q5, Q6 are connected in transistor Q2 via common source electrode, so two transistorized operation situations will be controlled by the bias voltage of electric current I t0.In addition, in common mode feedback circuit 14, then be provided with capacitor C c, the p type metal oxide semiconductor transistor Q13 of two couplings, Q14, the n-type metal oxide semiconductor transistor Q9 of two couplings, Q10, two grid biases are in the coupling n-type metal oxide semiconductor transistor Q11 of definite value direct voltage Vcm, the current source 19a of Q12 and two couplings, 19b, to realize the function of common-mode feedback compensation, just by transistor Q9, the grid of Q10 is the output signal Vo+ of receiving gain unit 12 outputs respectively, Vo-, and FEEDBACK CONTROL transistor Q7, the grid bias of Q8 is suitably to adjust differential output signal Vo+, the common mode electrical level of Vo-.
Amplifying circuit 10 realizes that the principle of variable gain can be described below.In gain unit 12, the input stage that is formed by transistor Q3, Q4 can be an output current with the voltage transduction of input signal Vi+, Vi-, and the transduction coefficient between output current and input voltage just depend on this two transistor bias current Ii0 (in fact be the evolution value that is proportional to Ii0, Ii0
0.5).The output current of input stage can flow into transistor Q5, the Q6 of active load, setting up output signal Vo+, Vo-on active load, and the resistive equivalent load size of this active load just depends on the bias current It0 (in fact being inversely proportional to the evolution value of It0) of transistor Q5, Q6.Comprehensive transduction and equivalent load as can be known, output signal (Vo+, Vo-) will depend on that with respect to the gain of input signal (Vi+, Vi-) electric current I i0 (is proportional to (Ii0/It0) to the ratio of electric current I t0
0.5).And can find out that by the configuration of gain control circuit 16 control signal Vc can change the difference between electric current I t0 and Ii0 via the shunting of transistor Q15, Q16, and then the gain of ride gain unit 12, realize out variable gain.For example, when the voltage of control signal Vc rises, electric current I t0 will reduce, and electric current I i0 then can relatively increase (because electric current I t0 with Ii0's and be constant definite value electric current I o), also makes the gain increasing of gain unit 12 jointly.On the contrary, if the voltage of control voltage Vc descends, electric current I t0 and Ii0 will increase respectively/reduce, and then make the gain controlled minimizing of gain unit 12.
But, the amplifying circuit 10 among the 2nd figure also has shortcoming.One of shortcoming lacks the gain ranging of broad exactly.Because the gain control circuit 16 in this amplifying circuit 10 is to distribute electric current I i0 and It0 by differential driving among the constant definite value electric current I o, so two electric current I t0, Ii0 only can change (one of them increase mutually in linear relationship, another just can only reduce linearly), make that the mutual difference degree of this two electric current I i0, It0 is limited, the difficult gain ranging that expands broadness.Also therefore, this traditional amplifying circuit often need be connected in series a plurality of gain units could realize being combined into bigger gain ranging, need take more layout area, consumes more power, also can reduce the frequency range of output signal.
Please refer to the 3rd figure, it is the variable-gain amplification circuit 20 (hereinafter to be referred as amplifying circuit 20) of another kind of traditional design, its design principle can be with reference to Q-H Duong, " An A11CMOS 84dB-Linear Low-Power Variable Gain Amplifier " (Sym.On VLSICircuits Digest of Technical Papers, 2005) of L-Quan and S-G Lee.Amplifying circuit 20 is biased between direct voltage Vdd and the G (for example being the ground terminal voltage), is differential output signal Vo+, Vo-so that differential input signal Vi+, Vi-are gained, and makes its big I that gains be controlled by the value of control signal Vc.Also be provided with gain unit 22, common mode feedback circuit 24 and gain control circuit 26 in the amplifying circuit 20.
Be similar to the gain unit 12 among the 2nd figure, gain unit 22 among the 3rd figure also forms input stage with receiving inputted signal Vi+, Vi-with n-type metal oxide semiconductor transistor T3, the T4 of two couplings, and forms active load to set up output signal Vo+, Vo-with n-type metal oxide semiconductor transistor T5, the T6 of two couplings.Transistor T 1 is with the bias current of electric current I i0 control input stage, and 2 bias currents with electric current I t0 control active load of transistor T, two transistor T7, the T8 of coupling then are used for the bias voltage of auxiliary input stage, active load.Similarly, be similar to the common mode feedback circuit 14 among the 2nd figure, in common mode feedback circuit 24, promptly realize the function of common-mode feedback compensation with current source 29a, the 29b of capacitor C c, each transistor T 9 to T14 and two couplings, just by output signal Vo+, the Vo-of the grid receiving gain unit 22 of transistor T 9, T10, suitably to adjust the common mode electrical level of differential output signal Vo+, Vo-via transistor T 7, T8.
By the circuit structure of gain unit 22 as can be known, amplifying circuit 20 also is to utilize the difference of electric current I i0, It0 to realize variable gain, makes its gain corresponding to the ratio of electric current I i0 to It0.But, different with the 2nd figure is, the gain control circuit 26 among the 3rd figure is to come difference between Control current Ii0, It0 in the mode of complementary drive.In gain control circuit 26, be provided with the p type metal oxide semiconductor transistor T 15 and n-type metal oxide semiconductor transistor T16 of complementary configured, these two transistorized grids all are controlled by control signal Vc, form the structure of complementary drive.The electric current I p0 of conducting can form electric current I t0 with the electric current I o addition that definite value current source 28a is provided on the transistor T 15, and n-type metal oxide semiconductor transistor T19 and transistor T 2 formed current mirrors just can provide bias current It0 with the active load in gain unit 22 with this electric current I t0 Mirroring Mapping to transistor T 2.In like manner, the electric current I n0 of conducting can add up to electric current I i0 with the electric current I o that another definite value current source 28b is provided on the transistor T 16, p type metal oxide semiconductor transistor T 17, T18 and the formed current mirror of n-type metal oxide semiconductor transistor T20, T1 just can provide bias current Ii0 with the input stage in gain unit 22 with this electric current I i0 Mirroring Mapping to transistor T 1.Therefore, when control signal Vc changed, the conducting degree of transistor T 15, T16 also can complementally change thereupon, and electric current I i0, It0 are changed, and then changed the gain of gain unit 22, realized out variable gain.
For example, when the voltage of control signal Vc raises, transistor T 16 can conductings multiple current and electric current I i0 is increased more, relatively 15 of transistor Ts can complementally reduce its conducting degree, make electric current I t0 reduce, therefore, cooperate the electric current I i0 of increase and the electric current I t0 of minimizing, the gain of gain unit 22 also will increase.
But, the amplifying circuit 20 among the 3rd figure also has shortcoming.One of its shortcoming, be exactly to the resistance of undesirable factor a little less than.By the structure of gain control circuit 26 as can be known, the difference between electric current I i0, It0 is to be controlled by the complementary drive of control signal Vc to transistor T 15, T16.Yet, because transistor T 15, T16 are respectively p type and n-type metal oxide semiconductor transistor, its circuit layout structure, related elements parameter (similarly are carrier mobility, mobility) and the step that is experienced in the processing procedure all inequality, so when undesirable factors such as experience process variation or variations in temperature, the degree of transistor T 15, the drift of T16 element characteristic can be not identical yet.Will make the situation of complementary drive depart from the situation of original design easily because of undesirable factor like this, the variable gain characteristic that makes amplifying circuit 20 is easier to be subjected to the influence of undesirable factor and the expection characteristic that can't meet original design.
In order to overcome the shortcoming of above-mentioned each amplifying circuit, the present invention will propose a variable-gain amplification circuit with preferred construction.Please refer to the 4th figure, it is the function block schematic diagram of amplifying circuit 30 of the present invention.Amplifying circuit 30 is a variable-gain amplification circuit, and it can be output signal with the input signal gain, and gain between the two can be adjusted by the value of control signal.For realizing variable gain, can be provided with gain unit 32 and gain control circuit 36 in the amplifying circuit 30 of the present invention.Can be provided with variable current circuit 38 and differential current circuit 40 in the gain control circuit 36.Then can be provided with input circuit 50 and load circuit 52 in the gain unit 32; If necessary, also can set up auxiliary circuit 42.In addition, amplifying circuit 30 also can design other relevant auxiliary circuit, for example, if will realize the amplifying circuit of differential I/O, just can optionally set up common mode feedback circuit 34 in amplifying circuit 30, to adjust the common mode electrical level in the differential output signal.
In gain control circuit 36 of the present invention, variable current circuit 38 can provide corresponding reference electric current I r according to control signal, makes the size of current of this reference current Ir be controlled by the value of control signal.40 in differential current circuit can split into load current It and input Control current Ii with reference current Ir according to control signal, makes load current It and imports the value that current difference between Control current Ii is controlled by this control signal.Owing to this load current It and input Control current Ii are gone out by reference current Ir shunting, thus electric current I i and electric current I t with also just be equivalent to reference current Ir.
In gain unit 32, load circuit 52 is used to provide active load, and this load circuit 52 can come bias voltage according to load current It, makes the equivalent load value of active load can be controlled by the size of load current It.50 input signals that are used for receiving variable-gain amplification circuit of input circuit, and can provide power conversions (similarly be the transduction, transconductance) input signal is converted to corresponding electric power (similarly be with input signal voltage transitions be electric current), this electric power is injected into load circuit 52, just can on load circuit 52, set up output signal, as the output of variable-gain amplification circuit 30.This input circuit 50 then can give bias voltage according to input Control current Ii, makes the power conversions degree (similarly being the value of transduction) of input circuit 50 can be controlled by the size of current of importing Control current Ii.
By above-mentioned discussion as can be known, the power conversions degree of input circuit 50 and the active load that load circuit 52 is provided are just depended in the gain of amplifying circuit 30 of the present invention, and these two factors are controlled by input Control current Ii and load current It respectively, therefore, change input Control current Ii and load current It, just can realize variable gain.And by gain control circuit 36 of the present invention as can be known, the present invention not only can make the difference of input Control current Ii and load current It is controlled by control signal in differential current circuit 40, also additionally utilized variable current circuit 38 and make this two electric current also be controlled by control signal with (being reference current Ir).So, not only can realize variable gain, also can further strengthen the mutual difference degree between input Control current and load current, make variable-gain amplification circuit of the present invention have the gain ranging of broad.
Continue the 4th figure, please continue with reference to the 5th figure, the 5th figure is to be a kind of execution mode that example illustrates amplifying circuit 30 of the present invention with the differential amplifier circuit.The amplifying circuit 30 of the 5th figure is biased between direct voltage Vdd and the G (for example being the ground terminal voltage), it can receive differential output signal Vo+, Vo-behind differential input signal Vi+, Vi-and the output gain, and the gain that differential output is gone between signal then can be adjusted by the value (similarly being magnitude of voltage) of control signal Vc.In the embodiment of the 5th figure, variable current circuit 38 can provide corresponding reference electric current I r according to the value of control signal Vc, and p type metal oxide semiconductor transistor M23, M24 and n-type metal oxide semiconductor transistor M25, M26 then are used for realizing differential current circuit 40 (please in the lump with reference to the 4th figure) in the mode of differential driving.Wherein, the grid of common source transistor M23, M24 is controlled by control signal Vc and another definite value direct voltage Vref as the reference signal respectively, splits into load current It and input Control current Ii with the reference current Ir that variable current circuit 38 is provided.For example, when the magnitude of voltage of control signal Vc was equivalent to definite value direct voltage Vref, electric current I t equated that with electric current I i both can divide equally reference current Ir.If the magnitude of voltage of control signal Vc is lower than voltage Vref, the conducting degree of transistor M23 will be higher than the conducting degree of transistor M24, from electric current I r more parts is branched to transistor M23, and relatively, the electric current that branches to transistor M24 will reduce.After the shunting via transistor M23, M24, transistor M25 can form current mirror with n-type metal oxide semiconductor transistor M2 in the gain unit 32, with load current It Mirroring Mapping to transistor M2, become load tail current ItT.In like manner, transistor M26 then with gain unit 32 in n-type metal oxide semiconductor transistor M1 form current mirror, will import Control current Ii Mirroring Mapping to transistor M1, on transistor M1, form input and control tail current IiT.
In the embodiment of the 5th figure, 32 of gain units are the input stage functions that two n-type metal oxide semiconductor transistor M3, M4 with coupling realize input circuit 50 (please in the lump with reference to the 4th figure), and the bias current of transistor M3, M4 just is controlled by the input control tail current IiT of conducting on the transistor M1 via the source electrode of interconnection.N-type metal oxide semiconductor transistor M5, the M6 of two couplings then are used for realizing load circuit 52 (with reference to the 4th figure) in addition, and the continuous transistorized bias current of these two source electrodes is just controlled by the load tail current ItT of the last conducting of transistor M2.In the gain unit 32 two coupling p type metal oxide semiconductor transistor M7, M8 then can be as auxiliary circuits 42, with the bias voltage of auxiliary input circuit 50 (transistor M3, M4), load circuit 52 (transistor M5, M6).In addition, in common mode feedback circuit 34, then realize the function of common-mode feedback compensation with capacitor C c, each transistor M9 to M14 and current source 39a, the 39b of two couplings, just by output signal Vo+, the Vo-of the grid receiving gain unit 22 of transistor M9, M10, suitably to adjust the common mode electrical level of differential output signal Vo+, Vo-via transistor M7, M8, voltage Vcm wherein is the definite value constant voltage.
The operating principle of amplifying circuit 30 can be described below among the 5th figure.When input signal Vi+, Vi-are imported by the grid of transistor M3, M4, the input circuit of being realized by these two transistors 50 changes applied signal voltage into electric current with regard to available transduction (mainly being the transduction value gm3 of transistor M3 or M4), and this transduction will be depended on the size of input control tail current IiT.The electric current of input circuit 50 transductions can be set up output signal Vo+, Vo-on the resistive equivalent load that transistor M5, M6 are provided, the value of this equivalent load (being mainly the inverse of the transduction gm5 of transistor M5, M6) then is controlled by the inverse of load current ItT.Therefore, the gain between input signal and output signal can be proportional to gm3/gm5.(in fact, the gm3 that transduces is proportional to (IiT) because transduction gm3, gm5 can be controlled by input control tail current IiT and load tail current ItT respectively
0.5Transduction gm5 is proportional to (ItT)
0.5), so gain just (that is to say that gain is proportional to (IiT/ItT) corresponding to importing the ratio I iT/ItT of control tail current IiT to load tail current ItT
0.5).Current mirror by transistor M1, M26 and M2, M25 concerns that as can be known input control tail current IiT also just is controlled by the ratio of input Control current Ii to load current It to the ratio of load tail current IiT.That is to say that the difference of adjusting between input Control current Ii and load current It is imported the ratio of Control current Ii to load current It to change, and just can adjust the gain of gain unit 32, realizes variable gain.
By above-mentioned discussion as can be known, as long as the mutual degree of variation of input Control current Ii and load current It enlarges, just can expand the gain ranging of broad.And the present invention not only can adjust difference between electric current I i and It according to the difference between control signal Vc and reference signal Vref in differential current circuit 40, can also be in variable current circuit 38 according to control signal Vc adjust electric current I i and It and, so the present invention can utilize more polynary mode to adjust the mutual degree of variation of electric current I i and It, and then expands the gain ranging of broad.
Please refer to the 6th figure.Continue the example of the 5th figure, further illustrated a kind of execution mode of variable current circuit 38 of the present invention among the 6th figure.Shown in the 6th figure, variable current circuit 38 of the present invention can realize with the complementary drive structure.In this embodiment, variable current circuit 38 can include the p type metal oxide semiconductor transistor M15 and the n-type metal oxide semiconductor transistor M16 of a pair of complementary configured, and the grid of two transistor is controlled by control signal Vc to form the structure of complementary drive; N-type metal oxide semiconductor transistor M19, M20 and p type metal oxide semiconductor transistor M18, M21 form current mirror, with the electric current I p Mirroring Mapping of transistor M15 institute conducting to transistor M21; P type metal oxide semiconductor transistor M17, M22 then form another current mirror, with the electric current I n Mirroring Mapping of transistor M16 institute conducting to transistor M22.At node Ns, the electric current I p of transistor M21, M22 Mirroring Mapping will collaborate to be in the same place with In, forms the reference current Ir that variable current circuit 38 is provided.Differential current circuit 40 just can split into input Control current Ii and load current It with this reference current Ir according to control signal Vc.
By the embodiment of the 6th figure as can be known, in the present invention, control signal Vc not only can control the poor of input Control current Ii and load current It via differential current circuit 40, also can be additionally by variable current circuit 38 control import Control current Ii, load current It's and (reference current Ir just).By this kind configuration, the present invention just can adjust mutual degree of variation between electric current I i and It in more polynary mode.About this situation, please continue with reference to the 7th figure (and in the lump with reference to the 6th figure), what it was illustrated is the control situation of control signal Vc to amplifying circuit 30 among the 6th figure.At first, by the variable current circuit 38 of complementary drive among the 6th figure as can be known, when control signal Vc increased progressively in rational control signal excursion, the curve that electric current I p roughly can follow second-degree parabola successively decreased, and electric current I n roughly can follow the curve of another second-degree parabola and increases progressively.Therefore, just as shown in the figure 7, reference current Ir (electric current that variable current circuit 38 provided just) will follow parabolic curve and change in the control signal excursion.In other words, in the present invention, input Control current Ii, load current It's and (electric current I r just) can change with control signal Vc.In comparison, in the amplifying circuit 10 in the 2nd figure, its input Control current Ii0, load current be It0's and be a constant definite value electric current I o only just.
Because reference current Ir also can change with control signal Vc, so the present invention can cause than the more electric current variation of prior art (similarly being the amplifying circuit 10 among the 2nd figure) at electric current I i, It, in identical control signal excursion, to expand the electric current range of variation of broad, just as shown in the figure 7.By previous discussion as can be known, amplifying circuit 30 of the present invention makes a variation by electric current and realizes variable gain, so the electric current range of variation increases, just can expand the gain ranging of broad jointly.Also therefore, the present invention is achieved out more broad gain ranging.
In addition, because the present invention has adopted the differential current circuit 40 of differential driving in gain control circuit 36, so amplifying circuit 36 of the present invention also can be kept the variable gain controlled characteristic of preferable (comparatively linear), and also has a preferable resistance to process variation, variations in temperature etc. are undesirable.Because differential current circuit 40 is to utilize two (being all the p type) of the same type transistor M23, M24 to drive out electric current I t, Ii respectively, so available comparatively linear curve is realized the controlled characteristic of variable gain.On the other hand, drive current It, Ii also can promote the resistivity of variable gain characteristic to undesirable factor to utilize two transistor M23 of the same type, M24 to come respectively.For example, when undesirable factor affecting amplifying circuit 30 of the present invention, the reference current Ir that variable current circuit 38 produces may depart from original design load, but, gain itself is to depend on the ratio I i/It of electric current I i to It, and when distributing electric current I i, It, because the component type of transistor M23, M24 is identical, so the element characteristic drift of equal extent can take place in both, so the drift of electric current I i, It can be repealed by implication when being converted to gain to a certain degree, reduces the influence of undesirable factor to the variable gain characteristic.
In summary, in variable-gain amplification circuit of the present invention, control signal Vc can via variable current circuit and differential current circuit influence respectively input Control current, load current and with poor, so can expand the difference of importing between Control current, load current in more polynary mode, realize out broad gain ranging, also can keep the controlled characteristic of preferable (linearity), and undesirable factors such as process temperatures are had preferable resistivity.Be stressed that at this variable current circuit 38 that the present invention illustrates in the 6th figure only is a kind of embodiment, the present invention also can adopt other kind to realize this variable current circuit 38 by controlled current source, to realize technical spirit of the present invention.
The above only is preferred embodiment of the present invention, and all equalizations of being done according to claim scope of the present invention change and modify, and all should belong to covering scope of the present invention.
Claims (9)
1. variable-gain amplification circuit, it includes:
Gain control circuit, it includes:
Variable current circuit, it can provide the corresponding reference electric current according to control signal, makes the value of the current value of this reference current corresponding to this control signal; And
The differential current circuit, it can split into load current and input Control current with this reference current according to this control signal, make this load current and this input Control current and be equivalent to this reference current, and make current difference between this load current and this input Control current be controlled by the value of this control signal; And
Described variable-gain amplification circuit also includes gain unit, and it includes:
Load circuit, in order to active load to be provided, this load circuit is to be biased in the load tail current, and the current value of this load tail current is the current value corresponding to this load current; And
Input circuit, be connected in this load circuit, this input circuit is in order to receiving inputted signal, and sets up output signal on this load circuit, this input circuit is to be biased in input control tail current, and the current value of this input control tail current is the current value corresponding to this input Control current.
2. variable-gain amplification circuit according to claim 1, wherein this load circuit is the load size that changes this active load according to the current value of this load tail current, and this input circuit to be current value according to this input control tail current provide transduction, transfer to this load circuit to change this output signal into electric current, and on the active load that this load circuit provides, set up this output signal according to this transduction.
3. variable-gain amplification circuit according to claim 1, wherein this input circuit can be set up differential output signal on this load circuit, and this variable-gain amplification circuit also includes:
Common mode feedback circuit is used for adjusting the common mode electrical level of this differential output signal.
4. variable-gain amplification circuit according to claim 1, this variable current circuit includes:
P type metal oxide semiconductor transistor, its grid is controlled by this control signal, makes this p type metal oxide semiconductor transistor that first electric current can be provided according to the value of this control signal; And
N-type metal oxide semiconductor transistor, its grid is controlled by this control signal, makes this n-type metal oxide semiconductor transistor that second electric current can be provided according to the value of this control signal;
Wherein this variable current circuit be according to this first electric current and this second electric current and this reference current is provided.
5. according to the variable-gain amplification circuit of claim 1, wherein this differential current circuit includes:
Two interconnected common source metal oxide semiconductor transistors of source electrode, its grid is controlled by this control signal and definite value reference signal respectively;
Wherein these two metal oxide semiconductor transistors are to receive this reference current jointly by the source electrode that is connected, with difference this load current of conducting in the drain electrode of each metal oxide semiconductor transistor and this input Control current.
6. method that realizes the variable gain amplifying technique, it is in order to adjust the gain between output signal and input signal according to control signal, and it includes this method:
Value according to this control signal provides reference current, makes the value of the current value of this reference current corresponding to this control signal;
According to this control signal this reference current is split into load current and input Control current, make this load current and this input Control current and be equivalent to this reference current, and make current difference between this load current and this input Control current be controlled by the value of this control signal; And
Value according to this input Control current and this load current gains this input signal so that this output signal to be provided accordingly.
7. method according to claim 6, wherein when gaining this input signal so that this output signal to be provided accordingly, be according to this input signal that gains of the ratio between this input Control current and this load current according to this value of importing Control current and this load current.
8. method according to claim 6 wherein in the time will providing this reference current according to this control signal, includes the following step:
This p type metal oxide semiconductor transistor make the transistorized grid of p type metal oxide semiconductor be controlled by this control signal, so that can provide first electric current according to the value of this control signal;
This n-type metal oxide semiconductor transistor make the grid of n-type metal oxide semiconductor transistor be controlled by this control signal, so that can provide second electric current according to the value of this control signal; And
According to this first electric current and this second electric current and this reference current is provided.
9. method according to claim 6 wherein in the time this reference current will being split into this load current and this input Control current, includes the following step:
In two interconnected common source metal oxide semiconductor transistors of source electrode, the source electrode input that is connected by these two metal oxide semiconductor transistors receives this reference current; And
Make the grid of one of them metal oxide semiconductor transistor be controlled by this control signal, and make the grid of another metal oxide semiconductor transistor then be controlled by the definite value reference signal, with difference this load current of conducting in the drain electrode of each metal oxide semiconductor transistor and this input Control current.
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| CNB2005101181630A CN100527609C (en) | 2005-10-26 | 2005-10-26 | Variable gain amplifying circuit and relative method |
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| CN100527609C true CN100527609C (en) | 2009-08-12 |
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| TWI462496B (en) | 2007-10-03 | 2014-11-21 | Airoha Tech Corp | The biasing circuit of the wireless transceiver |
| CN101150329B (en) * | 2007-10-16 | 2011-03-16 | 络达科技股份有限公司 | Radio transceiver bias circuit |
| US10236851B2 (en) * | 2016-11-17 | 2019-03-19 | Mediatek Inc. | Wide bandwidth variable gain amplifier and exponential function generator |
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| A 3.3-V CMOS wideband exponential controlvariable-gain-amplifier. Po-Chiun Huang, Li-Yu Chiou, Chorng-Kuang Wang.Circuits and Systems,Vol.vol.1 . 1998 * |
| An all CMOS 84dB-linear low-power variable gain amplifier. Quoc-Hoang Duong, Le-Quan, Sang-Gug Lee.VLSI Circuits. 2005 * |
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