CN203012575U - Current source circuit - Google Patents

Abstract

The utility model discloses a current source circuit, which comprises a positive temperature coefficient voltage generating sub-circuit, a threshold value voltage generating sub-circuit and a current generating sub-circuit, wherein the current generating sub-circuit comprises an amplifier and a first field effect tube; the positive temperature coefficient voltage generating sub-circuit is used for generating a first voltage which is the same as a temperature change trend; the first voltage is input into the reverse input end of the amplifier; the threshold value voltage generating sub-circuit is used for generating a second voltage having a fixed voltage value; the second voltage is input into the positive input end of the amplifier; the output end of the amplifier is connected with the grid of the first field effect tube; the source of the first field effect tube is connected with an external power supply; the drain of the first field effect tube is used for outputting the generated current; and the electron mobility of the first field effect tube is a process parameter which is opposite to the temperature change trend. Due to the adoption of the current source circuit disclosed by the utility model, the influences of temperature, voltage, processing technic, procedures and the like on the output current can be reduced effectively, and the stability and the accuracy of the output current are enhanced.

Description

Current source circuit

Technical field

The utility model relates to integrated circuit fields, relates more specifically to a kind of current source circuit.

Background technology

Current source is the elementary cell in integrated circuit, is widely used in various simulations and integrated digital circuit.The structure species of current source is various, but be all the voltage that adopts in most integrated circuit divided by resistance again the mode of mirror image produce the needed electric current of integrated circuit.The resistance of the current source that produces in this way is owing to being subject to temperature, voltage, the impact of processing technology and processing procedure etc., especially temperature is very large to the influence of peak current that produces, can produce the variation of 20% left and right, field effect transistor also exists variation in the parameter on different process border in addition, makes same circuit output current value have difference more than 30%.Therefore when producing in enormous quantities, the yield rate of product can be greatly affected, and the precision of the electric current of this current source generation does not reach the industry requirement yet.

Therefore, be necessary to provide a kind of improved current source circuit to overcome defects.

The utility model content

The purpose of this utility model is to provide a kind of current source circuit, and this current source circuit can effectively reduce temperature, voltage, the impact on output current such as processing technology and processing procedure, the stability and the accuracy that have improved output current.

for achieving the above object, the utility model provides a kind of current source circuit, it comprises that positive temperature coefficient voltages produces electronic circuit, threshold voltage produces electronic circuit and electric current produces electronic circuit, described electric current produces electronic circuit and comprises amplifier and the first field effect transistor, described positive temperature coefficient voltages produces electronic circuit and produces first voltage identical with temperature changing trend, and described the first voltage is inputed to the reverse input end of described amplifier, described threshold voltage produces electronic circuit and is connected with external power source, and produce the second voltage with fixed voltage value, and described second voltage is inputed to the positive input of described amplifier, the output terminal of described amplifier is connected with the grid of described the first field effect transistor, the source electrode of described the first field effect transistor is connected with external power source, the electric current that the drain electrode output of described the first field effect transistor produces, and the electron mobility of described the first field effect transistor is the technological parameter opposite with temperature changing trend.

Preferably, described electric current produces electronic circuit and also comprises the first resistance and the second resistance, described the first resistance is connected in described positive temperature coefficient voltages and produces between the reverse input end of electronic circuit and described amplifier, and described the second resistance is connected between the positive input of described threshold voltage generation electronic circuit and described amplifier.

Preferably, described current source circuit also comprises the 3rd resistance and the 4th resistance, and described the 3rd resistance is connected between the reverse input end and output terminal of described amplifier, and described the 4th resistance one end is connected with the positive input of described amplifier, other end ground connection.

preferably, described threshold voltage produces electronic circuit and comprises the second field effect transistor, the 3rd field effect transistor, the 4th field effect transistor, the first current source and the second current source, the grid of described the second field effect transistor, the grid of drain electrode and described the 3rd field effect transistor all is connected with an end of described the first current source, the other end ground connection of described the first current source, the source electrode of described the second field effect transistor, the grid of the drain electrode of the 3rd field effect transistor and described the 4th field effect transistor all is connected with an end of described the second current source, the other end ground connection of described the second current source, the drain electrode of described the 4th field effect transistor is connected with the source electrode of described the 3rd field effect transistor, the source electrode of described the 4th field effect transistor is connected with external power source, and second voltage is exported in the drain electrode of the source electrode of described the 3rd field effect transistor and described the 4th field effect transistor jointly.

Preferably, the breadth length ratio of described the second field effect transistor is identical with the breadth length ratio of described the 3rd field effect transistor, the breadth length ratio of described the first field effect transistor is identical with the breadth length ratio of described the 4th field effect transistor, and the breadth length ratio of described the first field effect transistor is 3 times of described the second field effect transistor breadth length ratio.

Preferably, the resistance of described the first resistance equates with the resistance of the 4th resistance, and the resistance of described the second resistance equates with the resistance of the 3rd resistance.

Preferably, described the first field effect transistor, the second field effect transistor, the 3rd field effect transistor and the 4th field effect transistor are P type field effect transistor.

Compared with prior art, current source circuit of the present utility model produces first voltage identical with temperature changing trend because described positive temperature coefficient voltages produces electronic circuit, and described the first voltage is inputed to the reverse input end of described amplifier, described the first field effect transistor is connected with described amplifier, and the electron mobility of described the first field effect transistor is the technological parameter opposite with temperature changing trend, and exports by the drain electrode of described the first field effect transistor the electric current that produces; Make electron mobility and described first voltage of described the first field effect transistor can mutually weaken or offset the other side because of the influence of peak current of temperature variation to output, the stability and the accuracy that have improved output current.

By following description also by reference to the accompanying drawings, it is more clear that the utility model will become, and these accompanying drawings are used for explaining the utility model.

Description of drawings

Fig. 1 is the structured flowchart of the utility model current source circuit.

Fig. 2 is the circuit theory diagrams of the utility model current source circuit.

Fig. 3 is the circuit theory diagrams that threshold voltage of the present utility model produces electronic circuit.

Embodiment

With reference now to accompanying drawing, describe embodiment of the present utility model, in accompanying drawing, similar element numbers represents similar element.As mentioned above, the utility model provides a kind of current source circuit, and this current source circuit can effectively reduce temperature, voltage, the impact on output current such as processing technology and processing procedure, the stability and the accuracy that have improved output current.

Please refer to Fig. 1, Fig. 1 is the structured flowchart of the utility model current source circuit.as shown in the figure, current source circuit of the present utility model comprises that positive temperature coefficient voltages produces electronic circuit, threshold voltage produces electronic circuit and electric current produces electronic circuit, described positive temperature coefficient voltages produces electronic circuit and produces first voltage identical with temperature changing trend, described threshold voltage produces electronic circuit and is connected with external power source, and produce the second voltage with fixed voltage value, and described the first voltage and second voltage input to respectively described electric current and produce electronic circuit, described electric current produces electronic circuit and is connected with external power source, described the first voltage with input, the voltage of second voltage and external power source input is converted into corresponding electric current output, and the electric current of output is met the requirements.

Particularly, please again in conjunction with reference to figure 2 and Fig. 3.

Described positive temperature coefficient voltages produces electronic circuit and produces first a voltage V identical with temperature changing trend _REF, it is that general positive temperature coefficient voltages commonly used produces circuit that wherein said positive temperature coefficient voltages produces electronic circuit, and is well known to those skilled in the art, and is not described in detail at this.

Described threshold voltage produces electronic circuit and comprises the second field effect transistor M _P1, the 3rd field effect transistor M _P2, the 4th field effect transistor M _P3, the first current source I1 and the second current source I2, described the second field effect transistor M _P1Grid, drain electrode and described the 3rd field effect transistor M _P2Grid all be connected with the end of described the first current source I1, the other end ground connection of described the first current source I1, described the second field effect transistor M _P1Source electrode, the 3rd field effect transistor M _P2Drain electrode and described the 4th field effect transistor M _P3Grid all be connected with the end of described the second current source I2, the other end ground connection of described the second current source I2, described the 4th field effect transistor M _P3Drain electrode and described the 3rd field effect transistor M _P2Source electrode connect, described the 4th field effect transistor M _P3Source electrode be connected with external power source VDD, and described the 3rd field effect transistor M _P2Source electrode and described the 4th field effect transistor M _P3Drain electrode jointly export second voltage V0; In preferred implementation of the present utility model, described the second field effect transistor M _P1Breadth length ratio and described the 3rd field effect transistor M _P2Breadth length ratio identical, and described the 4th field effect transistor M _P3Breadth length ratio be described the 3rd field effect transistor M _P23 times of breadth length ratio; Wherein, the electric current of described the second current source I2 output is 2 times of electric current of described the first current source I1 output, and the electric current that defines described the first current source I1 output is I, I ₂=2I ₁=2I.Produce in electronic circuit described the second field effect transistor M at threshold voltage of the present utility model _P1, the 3rd field effect transistor M _P2And the 4th field effect transistor M _P3Cooperatively interact, can make described the 4th field effect transistor M _P3The voltage of drain electrode output be outer power voltage VDD and any one field effect transistor (the second field effect transistor M _P1, the 3rd field effect transistor M _P2And the 4th field effect transistor M _P3In any one) threshold voltage V _THPDifference, i.e. V _O=V _DD-| V _THP|; And described the first current source I1, the second current source I2 are respectively the second field effect transistor M _P1, with the 3rd field effect transistor M _P2Electric current is provided.

Described electric current produces electronic circuit and comprises amplifier AMP and the first field effect transistor M _P, the reverse input end of described amplifier AMP produces electronic circuit with described positive temperature coefficient voltages and is connected, and its positive input produces electronic circuit with described threshold voltage and is connected, thus described the first voltage V _REFWith second voltage V0 respectively corresponding reverse input voltage and forward input voltage as described amplifier AMP input to described amplifier AMP, and amplify output terminal output voltage V by described amplifier AMP by described amplifier AMP _OUTDescribed the first field effect transistor M _PGrid be connected with the output terminal of described amplifier AMP, the source electrode of described the first field effect transistor is connected with external power source VDD, its drain electrode output design electric current I _REFIn preferred implementation of the present utility model, described electric current produces electronic circuit and also comprises the first resistance R ₁, the second resistance R ₂, the 3rd resistance R ₃With the 4th resistance R ₄And described amplifier AMP, the first resistance R 1, the second resistance R 2, the 3rd resistance R 3 and the 4th resistance R 4 have formed differential amplifier circuit jointly, thereby described amplifier AMP forward input voltage and reverse input voltage are subtracted each other, to obtain the output voltage V of described amplifier AMP in the designing requirement ratio _OUT, in addition, the resistance of described the first resistance R 1 equates with the resistance of the 4th resistance R 4, the resistance of the second resistance R 2 equates with the resistance of the 3rd resistance R 3, i.e. and R1=R4, R2=R3, therefore

Particularly, described the first resistance R ₁Be connected in described positive temperature coefficient voltages and produce between the reverse input end of electronic circuit and described amplifier AMP, described the 3rd resistance R ₃Be connected between the reverse input end and output terminal of described amplifier AMP, thus described the first resistance R ₁With described and three resistance R ₃Coordinate and regulate magnitude of voltage and described the first voltage V that is added on described amplifier AMP reverse input end _REFBetween proportionate relationship; Correspondingly, described the second resistance R ₂Be connected between the positive input of described threshold voltage generation electronic circuit and described amplifier AMP described the 4th resistance R ₄One end is connected with the positive input of described amplifier AMP, other end ground connection, thereby described the second resistance R ₂And the 4th resistance R ₄Can coordinate and regulate the magnitude of voltage be added on described amplifier AMP positive input and the proportionate relationship between described second voltage V0; Thereby in the utility model, can be by selecting the first resistance R of suitable big or small resistance ₁, the second resistance R ₂, the 3rd resistance R ₃With the 4th resistance R ₄, the output voltage V of regulating described amplifier AMP _OUTSize, and then make the electric current I of output _REFSize satisfy design requirement.Wherein, described the first field effect transistor M _PElectron mobility be the technological parameter opposite with temperature changing trend, thereby can partly or entirely offset the first voltage V that described positive temperature coefficient voltages produces electronic circuit output _REFBecause of temperature to output current I _REFImpact, guaranteed output current I _REFStability and accuracy.

In addition, in preferred implementation of the present utility model, described the first field effect transistor, the second field effect transistor, the 3rd field effect transistor and the 4th field effect transistor are P type field effect transistor.

The principle of work of the utility model current source circuit is described below in conjunction with Fig. 2 and Fig. 3.

The production process that produces the second voltage V0 of its output in electronic circuit at described threshold voltage is:

Described the second field effect transistor M _P1Source gate voltage V _SGP1For:

$V_{\mathrm{SGP}1}=V_{\mathrm{THP}}\sqrt{\frac{2I}{{\mathrm{\μ}}_p{c}_{\mathrm{ox}}{\left(\frac{W}{L}\right)}_1}}---\left(1\right)$

Wherein (W/L) ₁Be the first field effect transistor M _P1Breadth length ratio, μ _p, c _oxWith V _THPBe respectively the second field effect transistor M _P1Carrier mobility, gate oxide unit-area capacitance amount and threshold voltage are due in the field effect transistor of same batch, its carrier mobility, gate oxide unit-area capacitance amount and threshold voltage are all identical, or difference is very little, therefore described the 3rd field effect transistor M _P2With the 4th field effect transistor M _P3Carrier mobility, gate oxide unit-area capacitance amount and threshold voltage also all correspond to respectively μ _p, c _oxWith V _THP

For the 3rd field effect transistor M _P2:

$3I=\frac{1}{2}{\mathrm{\μ}}_p{c}_{\mathrm{ox}}{\left(\frac{W}{L}\right)}_2[2(V_{\mathrm{SGP}2}-|V_{\mathrm{THP}}\left|\right)V_{\mathrm{SDP}2}-{V_{\mathrm{SDP}2}}^2]---\left(2\right)$

Wherein (W/L) ₂, V _SGP2, V _SDP2Be the 3rd field effect transistor M _P2Breadth length ratio, source gate voltage, source-drain voltage.

For the 4th field effect transistor M _P3:

$V_{\mathrm{SGP}3}=V_{\mathrm{THP}}+\sqrt{\frac{6I}{{\mathrm{\μ}}_p{c}_{\mathrm{ox}}{\left(\frac{W}{L}\right)}_3}}---\left(3\right)$

Wherein (W/L) ₃Be the 4th field effect transistor M _P3Breadth length ratio, V _SGP3Be the 4th field effect transistor M _P3The source gate voltage.

Again due to

V _SGP3=V _SDP2+V _SGP1 （4）

V _O=V _DD-V _SGP3+V _SDP2 （5）

Separately, due to described the second field effect transistor M _P1Breadth length ratio and described the 3rd field effect transistor M _P2Breadth length ratio identical, and described the 4th field effect transistor M _P3Breadth length ratio be described the 3rd field effect transistor M _P23 times of breadth length ratio,

Convolution (1), (2), (3), (4), (5) can draw:

V _O=V _DD-|V _THP| （6）

The magnitude of voltage that namely draws second voltage V0 is V _DD-| V _THP|.

Due to R1=R4, therefore R2=R3 is the voltage V of described amplifier AMP output _OUTFor:

$V_{\mathrm{OUT}}=V_0-\frac{R_3}{R_1}{V}_{\mathrm{REF}}=V_{\mathrm{DD}}-\left|V_{\mathrm{THP}}\right|-\frac{R_3}{R_1}{V}_{\mathrm{REF}}---\left(7\right)$

Wherein, V _THPBe the first field effect transistor M _PThreshold voltage.

Described the first field effect transistor M _PThe electric current I of drain electrode output _REPFor:

$I_{\mathrm{REF}}=\frac{1}{2}{\mathrm{\μ}}_p{c}_{\mathrm{ox}}\frac{W}{L}{(V_{\mathrm{SGP}}-|V_{\mathrm{THP}}\left|\right)}^2=\frac{1}{2}{\mathrm{\μ}}_p{c}_{\mathrm{ox}}\frac{W}{L}{(V_{\mathrm{DD}}-V_{\mathrm{OUT}}-|V_{\mathrm{THP}}\left|\right)}^2---\left(8\right)$

μ wherein _p, c _oxWith V _THPBe respectively the first field effect transistor M _PCarrier mobility, gate oxide unit-area capacitance amount and threshold voltage; W/L, V _SGPBe respectively the first field effect transistor M _PBreadth length ratio, the source gate voltage.

In conjunction with (7) formula, (8) formula can draw:

$I_{\mathrm{REF}}=\frac{1}{2}{\mathrm{\μ}}_p{c}_{\mathrm{ox}}\frac{W}{L}{\left(\frac{R_3}{R_1}{V}_{\mathrm{REF}}\right)}^2---\left(9\right)$

(9) carrier mobility μ in formula _pIt is a technological parameter opposite with the variation tendency of temperature.And (9) gate oxide unit-area capacitance amount c in formula _ox, (W/L) ₂Be constant, and carrier mobility μ _pProduce voltage V with the positive temperature coefficient (PTC) voltage source _REFBe and the amount of temperature correlation, irrelevant for making output current and technique and temperature, (9) formula is necessary for zero to the partial derivative of temperature, thereby draws

$\frac{2}{V_{\mathrm{REF}}}\×\frac{\∂V_{\mathrm{REF}}}{\∂T}=-\frac{1}{(1/2){\mathrm{\μ}}_p{c}_{\mathrm{ox}}{(W/L)}_2}\×\frac{\∂\left[(1/2){\mathrm{\μ}}_p{c}_{\mathrm{ox}}{(W/L)}_2\right]}{\∂T}---\left(10\right)$

Again because

${\mathrm{\μ}}_p={\mathrm{\μ}}_0\×{\left(\frac{T}{T_0}\right)}^{-3/2}---\left(11\right)$

Wherein, T is the real work thermal voltage, T0=300K, μ ₀Be the carrier mobility at the T0 temperature.

In conjunction with (10) (11) two formulas, can draw

$\frac{{\∂V}_{\mathrm{REF}}}{\∂T}=\frac{1.5}{T_0\×V_{\mathrm{REF}}}---\left(12\right)$

Thereby only need positive temperature coefficient (PTC) voltage to produce the first voltage V of electronic circuit output _REFSatisfy (12) formula, the electric current I that draws from (9) formula _REFBe a temperature independent constant.Therefore the electric current of the utility model current source circuit generation not with technique and temperature variation, has improved output current I _REFStability and accuracy.

Abovely in conjunction with most preferred embodiment, the utility model is described, but the utility model is not limited to the embodiment of above announcement, and should contains various modification, equivalent combinations of carrying out according to essence of the present utility model.

Claims (7)

1. current source circuit, it is characterized in that comprising that positive temperature coefficient voltages produces electronic circuit, threshold voltage produces electronic circuit and electric current produces electronic circuit, described electric current produces electronic circuit and comprises amplifier and the first field effect transistor, described positive temperature coefficient voltages produces electronic circuit and produces first voltage identical with temperature changing trend, and described the first voltage is inputed to the reverse input end of described amplifier, described threshold voltage produces electronic circuit and is connected with external power source, and produce the second voltage with fixed voltage value, and described second voltage is inputed to the positive input of described amplifier, the output terminal of described amplifier is connected with the grid of described the first field effect transistor, the source electrode of described the first field effect transistor is connected with external power source, the electric current that the drain electrode output of described the first field effect transistor produces, and the electron mobility of described the first field effect transistor is the technological parameter opposite with temperature changing trend.

2. current source circuit as claimed in claim 1, it is characterized in that, described electric current produces electronic circuit and also comprises the first resistance and the second resistance, described the first resistance is connected in described positive temperature coefficient voltages and produces between the reverse input end of electronic circuit and described amplifier, and described the second resistance is connected between the positive input of described threshold voltage generation electronic circuit and described amplifier.

3. current source circuit as claimed in claim 2, it is characterized in that, also comprise the 3rd resistance and the 4th resistance, described the 3rd resistance is connected between the reverse input end and output terminal of described amplifier, described the 4th resistance one end is connected with the positive input of described amplifier, other end ground connection.

4. current source circuit as claimed in claim 1, it is characterized in that, described threshold voltage produces electronic circuit and comprises the second field effect transistor, the 3rd field effect transistor, the 4th field effect transistor, the first current source and the second current source, the grid of described the second field effect transistor, the grid of drain electrode and described the 3rd field effect transistor all is connected with an end of described the first current source, the other end ground connection of described the first current source, the source electrode of described the second field effect transistor, the grid of the drain electrode of the 3rd field effect transistor and described the 4th field effect transistor all is connected with an end of described the second current source, the other end ground connection of described the second current source, the drain electrode of described the 4th field effect transistor is connected with the source electrode of described the 3rd field effect transistor, the source electrode of described the 4th field effect transistor is connected with external power source, and second voltage is exported in the drain electrode of the source electrode of described the 3rd field effect transistor and described the 4th field effect transistor jointly.

5. current source circuit as claimed in claim 4, it is characterized in that, the breadth length ratio of described the second field effect transistor is identical with the breadth length ratio of described the 3rd field effect transistor, the breadth length ratio of described the first field effect transistor is identical with the breadth length ratio of described the 4th field effect transistor, and the breadth length ratio of described the first field effect transistor is 3 times of described the second field effect transistor breadth length ratio.

6. current source circuit as claimed in claim 4, is characterized in that, the resistance of described the first resistance equates with the resistance of the 4th resistance, and the resistance of described the second resistance equates with the resistance of the 3rd resistance.

7. current source circuit as claimed in claim 4, is characterized in that, described the first field effect transistor, the second field effect transistor, the 3rd field effect transistor and the 4th field effect transistor are P type field effect transistor.

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