CN102722205A - A low-voltage band-gap reference generating circuit - Google Patents

Abstract

The invention relates to a low-voltage band-gap reference generating circuit, comprising resistors R2 and R3 that are connected with a current output end of a current mirror module, a bipolar transistor Q3 with an emitting electrode connected with R2, a positive temperature rate current generating module that generates positive temperature coefficient current and connects a current input end of the current mirror module, and a bipolar transistor Q3 with the emitting electrode connected to R2, wherein a sum of a voltage between two ends of R2 and the voltage between a base electrode and an emitting electrode of Q3 does not change along with temperature due to resistance of R2; a voltage input end of the current mirror module is connected to supply voltage; the other end of the positive temperature rate current generating module, the base electrode and a collector electrode of Q3, and the other end of R3 are all grounded; the supply voltage is less than 1.5 Volt; and the voltage between two ends of R3 are output voltage. The circuit can generate band-gap reference voltage satisfying requirements of zero temperature coefficient with supply voltage less than 1.5 Volt.

Description

A kind of low pressure band gap reference generating circuit

Technical field

The present invention relates to the reference circuit field, particularly relate to a kind of low pressure band gap reference generating circuit.

Background technology

The main effect of reference circuit is reference voltage or the reference current that in integrated circuit, provides stable; This just requires reference circuit insensitive to the variation and the variation of temperature of supply voltage; It is the variation of the supply voltage of reference circuit; And the variation of ambient temperature, can the reference voltage or the reference current of this reference circuit output do not exerted an influence.In all benchmark; Band-gap reference is most popular a kind of; It has and the almost irrelevant outstanding advantage of supply voltage, technology, temperature variation, thereby is widely used in high-precision comparer, A/D or D/A converter, LDO voltage stabilizer and other the many Analogous Integrated Electronic Circuits.

Existing band-gap reference generation circuit has certain requirement to the minimum of supply voltage; Promptly have only to use and be higher than 1.5 volts supply voltage; Just might produce the bandgap voltage reference that not influenced by temperature and mains voltage variations; If supply voltage is lower than 1.5 volts, then the voltage of output will not meet the requirement of zero-temperature coefficient (zero TC), and promptly output voltage will change along with the variation of ambient temperature; Such output voltage just can not satisfy the basic demand of reference voltage, has also just limited the application of this band-gap reference generation electric current under the low supply voltage condition in the prior art.

Summary of the invention

Technical matters to be solved by this invention provides a kind of low pressure band gap reference generating circuit, can utilize the supply voltage that is lower than 1.5 volts to produce and meet the bandgap voltage reference that zero-temperature coefficient requires.

The technical scheme that the present invention solves the problems of the technologies described above is following: a kind of low pressure band gap reference generating circuit, and this circuit comprises: current mirror module, positive temperature rate current generating module, No. two resistance R 2, the 3rd transistor Q3, No. three resistance R 3, wherein,

Said current mirror module comprises: voltage input end, current input terminal and current output terminal;

Said positive temperature rate current generating module has No. seven ends and No. eight ends, and its No. seven end links to each other with the current input terminal of said current mirror module; Said positive temperature rate current generating module is used to produce the electric current with positive temperature coefficient (PTC);

R2 has No. three ends and No. four ends, and its No. three end links to each other with the current output terminal of current mirror module;

Q3 is a bipolar transistor; The emitter of Q3 links to each other with No. four ends of R2; The resistance of R2 satisfies does not change the voltage at R2 two ends and the base stage of Q3 and the voltage sum between the emitter with variation of temperature;

R3 has No. five ends and No. six ends; No. five ends of R3 link to each other with No. three ends of R2;

The voltage input end of said current mirror module is as the supply voltage input end; No. six ends of No. eight ends of said positive temperature rate current generating module, the base stage of Q3 and collector, R3 all are connected with the ground end; Voltage between said supply voltage input end and the ground end is lower than 1.5 volts; The voltage at R3 two ends is the reference voltage of output.

The invention has the beneficial effects as follows: among the present invention; Because positive temperature rate current generating module can produce the electric current with positive temperature coefficient (PTC); This electric current is connected to the current input terminal of current mirror module, can obtains onesize and output current direction at the current output terminal of current mirror module, like this; After R2 and the Q3 series connection again with the circuit of R3 parallel connection owing to link to each other with the current output terminal of current mirror module, the electric current I that its input current is promptly produced with positive temperature rate current generating module _PTATIdentical, and, though the electric current that flows through R2 compares I through shunting _PTATSmaller, but also have positive temperature coefficient (PTC), thereby the voltage at R2 two ends just has positive temperature coefficient (PTC); According to transistor working principle, the base stage of bipolar transistor Q3 and the voltage V between the emitter _BE3Has negative temperature coefficient; The resistance of R2 also satisfies does not change the voltage at R2 two ends and the base stage of Q3 and the voltage sum between the emitter with variation of temperature; Therefore; The voltage at R3 two ends, be that the output voltage of this circuit has not just changed with variation of temperature yet; Be lower than at the supply voltage that the voltage input end of current mirror module inserts under 1.5 volts the situation, output voltage of the present invention just is the bandgap voltage reference that meets the zero-temperature coefficient condition.

On the basis of technique scheme, the present invention can also do following improvement:

Further, said current mirror module further has control end and No. two current output terminals;

Said positive temperature rate current generating module comprises: big gain operational amplifier, the first transistor Q1, transistor seconds Q2, a resistance R 1 that has an end and hold for No. two; Wherein, Q1 and Q2 are bipolar transistor; The end of R1 links to each other with the emitter of Q1; No. two ends of R1 link to each other with the positive input of big gain operational amplifier and the current input terminal of current mirror module respectively; The emitter of Q2 links to each other with the negative input of big gain operational amplifier and No. two current output terminals of current mirror module respectively; The emitter current density of Q2 be Q1 emitter current density n doubly, n is the natural number greater than 1; The output of said big gain operational amplifier links to each other with the control end of said current mirror module, is used to make the electric current of No. two current output terminals of said current mirror module to equal the electric current of its current input terminal; The base stage of the base stage of Q1 and collector, Q2 all is connected with the ground end with collector.

Further, the resistance of R2 is satisfied makes the voltage at R2 two ends and base stage and the voltage sum between the emitter of Q3 with the method that variation of temperature changes not be: the base stage of Q3 and the voltage V between the emitter _BE3, Q1 and Q2 thermoelectrical potential V _T, satisfy relational expression between absolute temperature T and R1, R2, the n:

Wherein,

Be V _BE3T is asked the resulting local derviation value of local derviation.

Further, the voltage at R3 two ends is

Further, said current mirror module comprises: the first FET MP1, the second FET MP2, the 3rd FET MP3;

MP1, MP2 and MP3 are the PMOS FET;

The source electrode of MP1, MP2 and MP3 all links to each other, as the voltage input end of said current mirror module;

The grid of MP1, MP2 and MP3 all links to each other, as the control end of said current mirror module;

The drain electrode of MP1 is as No. two current output terminals of said current mirror module;

The drain electrode of MP2 is as the current input terminal of said current mirror module, and the drain electrode of MP3 is the current output terminal of said current mirror module.

Further, T is between 233.15 Kelvin to 358.15 Kelvins.

Description of drawings

Fig. 1 is the structural drawing of low pressure band gap reference generating circuit provided by the invention;

Fig. 2 is the structural drawing of an embodiment of low pressure band gap reference generating circuit provided by the invention;

Fig. 3 is the synoptic diagram that is operated in the bipolar transistor under the unequal current density;

Fig. 4 produces the output voltage of circuit and the graph of a relation between the temperature for the band-gap reference provided by the invention that scanning emulation obtains;

Fig. 5 produces the output voltage of circuit and the graph of a relation between the supply voltage for the band-gap reference provided by the invention that scanning emulation obtains;

Fig. 6 is the structural drawing of another embodiment of low pressure band gap reference generating circuit provided by the invention.

Embodiment

Below in conjunction with accompanying drawing principle of the present invention and characteristic are described, institute gives an actual example and only is used to explain the present invention, is not to be used to limit scope of the present invention.

Fig. 1 is the structural drawing of low pressure band gap reference generating circuit provided by the invention.As shown in Figure 1, this circuit comprises: current mirror module, positive temperature rate current generating module, No. two resistance R 2, the 3rd transistor Q3, No. three resistance R 3, wherein,

Current mirror module comprises: voltage input end, current input terminal and current output terminal;

Positive temperature rate current generating module has No. seven ends and No. eight ends, and its No. seven end links to each other with the current input terminal of current mirror module; Positive temperature rate current generating module is used to produce the electric current with positive temperature coefficient (PTC);

R2 has No. three ends and No. four ends, and its No. three end links to each other with the current output terminal of current mirror module;

Q3 is a bipolar transistor; The emitter of Q3 links to each other with No. four ends of R2; The resistance of R2 satisfies does not change the voltage at R2 two ends and the base stage of Q3 and the voltage sum between the emitter with variation of temperature;

R3 has No. five ends and No. six ends; No. five ends of R3 link to each other with No. three ends of R2;

The voltage input end of current mirror module is as the supply voltage input end; No. six ends of No. eight ends of positive temperature rate current generating module, the base stage of Q3 and collector, R3 all are connected with the ground end; Voltage between supply voltage input end and the ground end is lower than 1.5 volts; The voltage at R3 two ends is the reference voltage of output.

Here, current mirror module is the module with current mirror function, and it is one of element circuit the most basic in the Analogous Integrated Electronic Circuits.Current mirror module is the circuit that a kind of electric current of the current input terminal with this module reappears or duplicates at current output terminal; Be that the current input terminal of current mirror module and the electric current of current output terminal are identical; This means if the direction of current of the current input terminal of current mirror module flows out from current input terminal; The direction of current of that current output terminal also flows out from current output terminal; And the size of current of the two equates, otherwise, if the direction of current of the current input terminal of current mirror module flows into to current input terminal; The direction of current of that current output terminal also flows into to current output terminal, and the size of current of the two also equates.Therefore; The electric current at No. seven end places of positive temperature rate current generating module that current input terminal connected of current mirror module is that the electric current at No. three end places of R2 that are connected with its current output terminal is identical, is equal to the electric current I with positive temperature coefficient (PTC) that positive temperature rate current generating module is produced _PTAT

As shown in Figure 1, R2 is with after Q3 connects, and is parallelly connected with R3 again, the voltage at these circuit two ends, i.e. the voltage V at R3 two ends _BG, be the output voltage of whole low pressure band gap reference generating circuit.At the electric current output point of current mirror module, i.e. R2 No. three ends or No. five of R3 ends, electric current I _PTATShunt, flow to R2 place branch road and R3 respectively, at this moment, the electric current that flows into the R2 branch road belongs to I _PTATA part, thereby this electric current also has positive temperature coefficient (PTC), like this, the voltage at R2 two ends has just had positive temperature coefficient (PTC).

If the voltage and one at R2 two ends is had the voltage addition of negative temperature coefficient, promptly might obtain a temperature independent bandgap voltage reference, among Fig. 1, the base stage of bipolar transistor Q3 and the voltage V between the emitter _BE3Just be a voltage with negative temperature coefficient; Be lower than at supply voltage under 1.5 volts the situation,, make it satisfy voltage and the base stage of Q3 and the voltage sum between the emitter that makes the R2 two ends through the resistance of R2 accurately is set; Do not change with variation of temperature; Just can make the output voltage at R3 two ends, the output voltage of promptly whole low pressure band gap reference generating circuit meets the requirement of zero-temperature coefficient, does not change with variation of temperature.Like this, be lower than at supply voltage under 1.5 volts the situation, output voltage of the present invention is just for to have met the bandgap voltage reference of zero-temperature coefficient condition.

Fig. 2 is the structural drawing of an embodiment of low pressure band gap reference generating circuit provided by the invention.As shown in Figure 2, this embodiment aligns temperature rate current generating module to have carried out further qualification on the basis of Fig. 1, and among this embodiment, current mirror module has control end and No. two current output terminals;

Positive temperature rate current generating module comprises: big gain operational amplifier, the first transistor Q1, transistor seconds Q2, a resistance R 1 that has an end and hold for No. two; Wherein, Q1 and Q2 are bipolar transistor; The end of R1 links to each other with the emitter of Q1; No. two ends of R1 link to each other with the positive input of big gain operational amplifier and the current input terminal of current mirror module respectively; The emitter of Q2 links to each other with the negative input of big gain operational amplifier and No. two current output terminals of current mirror module respectively; The emitter current density of Q2 be Q1 emitter current density n doubly, n is the natural number greater than 1; The output of big gain operational amplifier links to each other with the control end of current mirror module, is used to make the electric current of No. two current output terminals of current mirror module to equal the electric current of its current input terminal; The base stage of the base stage of Q1 and collector, Q2 all is connected with the ground end with collector.

Operational amplifier among Fig. 2 is big gain operational amplifier, and therefore, its positive input and negative input are in empty disconnected state; Be that the two voltage is identical, but do not have electric current from passing through between the two, like this; The emitter of Q2 is identical with the voltage of No. two ends of R1; And do not have electric current to pass through between the two, No. two ends of R1 are equivalent to No. seven ends of positive temperature rate current generating module among Fig. 1, and the base stage of Q1 and collector; And the base stage of Q2 and collector, then be equivalent to just hold for No. eight of temperature rate current generating module among Fig. 1.The output of big gain operational amplifier links to each other with the control end of current mirror module; Can make the electric current of No. two current output terminals of current mirror module equal the electric current of its current input terminal; Like this; Among Fig. 2, the electric current at the electric current at the electric current at the emitter place of Q2, No. two end places of R1 and No. three end places of R2 is just identical, is equal to I _PTAT, and because the positive input of big gain operational amplifier and negative input are emptyly to lack, thereby the voltage at voltage and No. two end places of R1 at the emitter place of Q2 also is identical among Fig. 2.

If the base stage of Q1, Q2 and the voltage between the emitter are respectively V _BE1And V _BE2, the voltage at R1 two ends is (V so _BE2-V _BE1), and the voltage of No. two of R1 ends will be higher than the voltage of an end, therefore, and I _PTATSize do

Flow to one of which number end from No. two ends of R1.

Q1 and Q2 are bipolar transistor, therefore, according to transistor working principle, under the emitter current density condition of different of Q1 and Q2, the voltage difference (V between its base stage and the emitter _BE2-V _BE1) just having positive temperature coefficient (PTC), its principle can reflect through Fig. 3.

Fig. 3 is the synoptic diagram that is operated in the bipolar transistor under the unequal current density.As shown in Figure 3, Q _BBe a bipolar transistor Q, its base stage and earth terminal again after collector links to each other, Q _ABe the parallel connection of n bipolar transistor Q, n is the natural number greater than 1, and promptly the emitter of n Q all links to each other, and collector links to each other respectively with base stage and then links to each other with the ground end.

Among Fig. 3, at Q _BAnd Q _AEmitter current identical and be under the situation of I because Q _ABy n and Q _BIdentical bipolar transistor Q is formed in parallel, therefore, and Q _BEmitter current density be Q just _AN doubly, according to the principle of work of bipolar transistor, can obtain Q _BWith Q _ABase stage and the voltage V between the emitter _BE-BAnd V _BE-ADifference do

$\mathrm{\Δ}{V}_{\mathrm{BE}}=(V_{\mathrm{BE}-B}-V_{\mathrm{BE}-A})=V_T\ln \left(\frac{n{I}_C}{I_S}\right)-V_T\left(\frac{I_C}{I_S}\right)=V_T\ln n---\left(1\right)$

In the formula (1), V _TBe the thermoelectrical potential of bipolar transistor Q, it is directly proportional with absolute temperature T; I _cCollector current for bipolar transistor Q; I _sSaturation current for bipolar transistor Q.

Local derviation is asked to T in formula (1) two ends, can get

$\frac{\∂\mathrm{\Δ}{V}_{\mathrm{BE}}}{\∂T}=\frac{\∂V_T}{\∂T}\·\ln n=\frac{V_T}{T}\·\ln n---\left(2\right)$

In the formula (2), because V _TBe directly proportional with T, therefore, V _TT is asked local derviation, be equivalent to use V _TDivided by T.Can find out by expression formula (2), the value of this formula gained be on the occasion of, this means the difference Δ V of the voltage of the base stage that is operated in two bipolar transistors under the different electric current density and emitter _BEIncrease along with the increase of absolute temperature T,, promptly have positive temperature coefficient (PTC) along with reducing of T.

Therefore, the difference of the voltage between the Q2 among Fig. 2 and the base stage of Q1 and the emitter just has positive temperature coefficient (PTC), through the electric current I of R1 _PTATAnd the electric current I that flows out from the current output terminal of current mirror module _PTATAlso all have positive temperature coefficient (PTC), and have following formula to set up:

$I_{\mathrm{PTAT}}=\frac{V_{\mathrm{BE}2}-V_{\mathrm{BE}1}}{{\mathrm{<figure-callout\; id="1"\; label="R"\; filenames="HDA0000052581080000022.png,HDA0000052581080000031.png"\; state="\{\{state\}\}">R</figure-callout>}}_1}=\frac{V_T\ln n}{R_1}---\left(3\right)$

In the formula (3), V _TThermoelectrical potential for bipolar transistor Q1 and Q2.

Like Fig. 1, shown in 2, R2 is with after Q3 connects, and parallelly connected with R3 again, the output voltage of this circuit is the output voltage V of whole low pressure band gap reference generating circuit _BGAt the electric current output point of current mirror module, i.e. R2 No. three ends or No. five of R3 ends, electric current I _PTATShunt, flow to R2 and R3 respectively, at this moment, the one part of current that flows into R2 belongs to I _PTATA part, thereby this electric current also has positive temperature coefficient (PTC), like this, the voltage at R2 two ends has just had positive temperature coefficient (PTC).

Supply voltage in input is lower than under the situation of 1.5V; The voltage and one that the R2 two ends are had a positive temperature coefficient (PTC) has the voltage addition by a certain percentage of negative temperature coefficient; Through the resistance of R2 accurately is set, be to obtain one with the irrelevant bandgap voltage reference of absolute temperature T.Among Fig. 1 and Fig. 2, the base stage of bipolar transistor Q3 and the voltage V between the emitter _BE3Just be the voltage with negative temperature coefficient, can explain through following formula: the principle of work by bipolar transistor can be known V _BE3Ask local derviation to be to absolute temperature T:

$\frac{\&PartialD;V_{\mathrm{BE}3}}{\&PartialD;T}=\frac{V_{\mathrm{BE}3}-(m+4)V_T-(E_g/q)}{T}---\left(4\right)$

In the formula (4), m is the humidity index of mobility, is one and is about 1.5 constant; V _TThermoelectrical potential for Q3; E _gFor making the semi-conductive band-gap energy of Q3, process by silicon usually like Q3, then its E _gBe about 1.12 electron volts; Q is the quantity of electric charge of electronics, also is constant.

The value that formula (4) calculates is a negative value, below with absolute temperature T=300 Kelvins, promptly 27 degrees centigrade situation is an example, this moment V _TBe about 26 millivolts, the base stage of the Q3 of silicon system and the voltage V between the emitter _BE3=750 millivolts, then the result of calculation of formula (4) is about-1.5mV/K, is negative value.

The result of calculation of formula (4) is negative value, means the base stage of bipolar transistor Q3 and the voltage V between the emitter _BE3Just reduce, increase, be a voltage with negative temperature coefficient along with reducing of T along with the increase of T.

Down in the face of the current output terminal of current mirror module, be No. three ends of R2 or No. five end row node current equations of R3, can get:

$\frac{{\mathrm{<figure-callout\; id="3"\; label="V\; BG\; R"\; filenames="HDA0000052581080000011.png,HDA0000052581080000022.png"\; state="\{\{state\}\}">V</figure-callout>}}_{\mathrm{BG}}}{R_{}}+\frac{V_{\mathrm{BG}}-V_{\mathrm{BE}3}}{{\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="HDA0000052581080000031.png"\; state="\{\{state\}\}">R</figure-callout>}}_2}=I_{\mathrm{PTAT}}---\left(5\right)$

With formula (3) substitution formula (5), and be out of shape:

$V_{\mathrm{BG}}=\frac{R_3}{{\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="HDA0000052581080000031.png"\; state="\{\{state\}\}">R</figure-callout>}}_2+R_3}(V_{\mathrm{BE}3}+I_{\mathrm{PTAT}}\&CenterDot;R_2)=\frac{R_3}{{\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="HDA0000052581080000031.png"\; state="\{\{state\}\}">R</figure-callout>}}_2+R_3}(V_{\mathrm{BE}3}+\frac{V_T{R}_2}{{\mathrm{<figure-callout\; id="1"\; label="R"\; filenames="HDA0000052581080000022.png,HDA0000052581080000031.png"\; state="\{\{state\}\}">R</figure-callout>}}_1}\ln n)---\left(6\right)$

In the formula (6), V _BE3Can know for having the voltage of negative temperature coefficient by formula (4), and

For being proportional to V _TThe voltage with positive temperature coefficient (PTC); Therefore; Emitter current density that can be through Q2 reasonably is set is to the value of multiple n and the R1 and the R2 of the emitter current density of Q1, makes that the result of gained is the voltage with zero-temperature coefficient after these two voltage additions, and promptly this voltage does not change with variation of temperature; At this moment, the output voltage V of this circuit _BGAlso for having the voltage of zero-temperature coefficient.Further, can be through R3 reasonably be set, the voltage V that formula (6) is calculated _BGLess than the resulting output bandgap voltage reference of prior art, so just can reduce requirement to supply voltage, make the employed supply voltage of this circuit be lower than 1.5 volts.

Local derviation is asked to T in formula (6) two ends, can get:

$\frac{\&PartialD;V_{\mathrm{BG}}}{\&PartialD;T}=\frac{R_3}{{\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="HDA0000052581080000031.png"\; state="\{\{state\}\}">R</figure-callout>}}_2+R_3}(\frac{\&PartialD;V_{\mathrm{BE}3}}{\&PartialD;T}+\frac{{\mathrm{<figure-callout\; id="2"\; label="V\; T\; R"\; filenames="HDA0000052581080000031.png"\; state="\{\{state\}\}">V</figure-callout>}}_T{R}_{}{}_2\ln n}{T{R}_1})---\left(7\right)$

In the formula (7),

Be V _BE3T is asked the resulting local derviation value of local derviation.

For making V _BGHas zero-temperature coefficient; Then formula (7) should equal 0; Like this, the part in formula (7) bracket also just should equal 0, therefore; The resistance of R2 satisfies voltage and the base stage of Q3 and the method that the voltage sum between the emitter does not change with variation of temperature that makes the R2 two ends, the output voltage V of the low pressure band gap reference generating circuit that the present invention just proposes _BGCondition with zero-temperature coefficient is:

$\frac{\&PartialD;V_{\mathrm{BE}3}}{\&PartialD;T}+\frac{{\mathrm{<figure-callout\; id="2"\; label="V\; T\; R"\; filenames="HDA0000052581080000031.png"\; state="\{\{state\}\}">V</figure-callout>}}_T{R}_{}{}_2\mathrm{<figure-callout\; id="1"\; label="ln\; n\; TR"\; filenames="HDA0000052581080000022.png,HDA0000052581080000031.png"\; state="\{\{state\}\}">ln</figure-callout>}n}{{\mathrm{TR}}_{}}=0---\left(8\right)$

In the formula (8), V _BE3Be the base stage of Q3 and the voltage between the emitter, V _TBe the thermoelectrical potential of Q1 and Q2, T is an absolute temperature,

Be V _BE3T is asked the resulting local derviation value of local derviation.

Again with T=300K, be example promptly 27 degrees centigrade situation, at this moment, Q1, Q2 and three transistorized thermoelectrical potential V of Q3 _TBe 26 millivolts, V _BE3=750 millivolts, Be about-1.5mV/K, R2 gets 5 with the ratio of the resistance of R1, and n gets 31, and then formula (8) is just set up, and formula (7) just equals 0, utilizes the output voltage V of this circuit that formula (6) calculates _BGJust for having the bandgap voltage reference of zero-temperature coefficient.

Under the situation that has satisfied above-mentioned zero-temperature coefficient condition, the voltage at R 3 two ends, the output voltage of low pressure band gap reference generating circuit promptly proposed by the invention is shown in the formula (6) just

$V_{\mathrm{BG}}=\frac{R_3}{{\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="HDA0000052581080000031.png"\; state="\{\{state\}\}">R</figure-callout>}}_2+R_3}(V_{\mathrm{BE}3}+\frac{V_T{R}_2}{{\mathrm{<figure-callout\; id="1"\; label="R"\; filenames="HDA0000052581080000022.png,HDA0000052581080000031.png"\; state="\{\{state\}\}">R</figure-callout>}}_1}\ln n).$

Choose R3, it is satisfied

Carry it into formula (6) and calculate, can get: V _BGBe about 0.9V, obviously required here supply voltage has reduced widely.

Fig. 4 produces the output voltage of circuit and the graph of a relation between the temperature for the band-gap reference provided by the invention that scanning emulation obtains.As shown in Figure 4, horizontal ordinate is the temperature that unit is degree centigrade, can be scaled absolute temperature through common practise, and ordinate is the output voltage V BG that band-gap reference provided by the invention produces circuit.Can find out through simulation result shown in Figure 4; The output voltage V BG of this circuit is zero with the variation of temperature rate near the normal temperature of 20 deg.c basically; In-40 degrees centigrade to 85 degrees centigrade temperature range, its temperature coefficient is about 8ppm/ ℃, and the ppm in the unit represents 1,000,000/; In range of application of the present invention, can think that output voltage V BG has zero-temperature coefficient.Above-mentioned Celsius temperature is scaled absolute temperature, can knows: in the scope of absolute temperature T of the present invention between 233.15 Kelvin to 358.15 Kelvins, can guarantee output voltage V _BGHas zero-temperature coefficient.

Fig. 5 produces the output voltage of circuit and the graph of a relation between the supply voltage for the band-gap reference provided by the invention that scanning emulation obtains.As shown in Figure 5, horizontal ordinate is supply voltage VDD, and ordinate is the output voltage V BG that band-gap reference provided by the invention produces circuit; Can be known that by Fig. 5 the present invention is minimum to be operated under the supply voltage of 0.95V, the benchmark output voltage of generation is about 0.75V; This shows; The present invention greatly reduces band-gap reference and produces the requirement of circuit to supply voltage, even supply voltage is low to moderate below 1 volt, its output voltage is still for satisfying the bandgap voltage reference of zero-temperature coefficient condition.

This shows; Among the present invention,, this electric current is connected to the current input terminal of current mirror module because positive temperature rate current generating module can produce the electric current with positive temperature coefficient (PTC); Can obtain onesize at the current output terminal of current mirror module and output current direction; Like this, after R2 and the Q3 series connection again with the circuit of R3 parallel connection owing to link to each other with the current output terminal of current mirror module, the electric current I that its input current is promptly produced with positive temperature rate current generating module _PTATIdentical, and, though the electric current that flows through R2 compares I through shunting _PTATSmaller, but also have positive temperature coefficient (PTC), thereby the voltage at R2 two ends just has positive temperature coefficient (PTC); According to transistor working principle, the base stage of bipolar transistor Q3 and the voltage V between the emitter _BE3Has negative temperature coefficient; The resistance of R2 also satisfies does not change the voltage at R2 two ends and the base stage of Q3 and the voltage sum between the emitter with variation of temperature; Therefore; The voltage at R3 two ends, be that the output voltage of this circuit has not just changed with variation of temperature yet; Be lower than at the supply voltage that the voltage input end of current mirror module inserts under 1.5 volts the situation, output voltage of the present invention just is the bandgap voltage reference that meets the zero-temperature coefficient condition.

Fig. 6 is the structural drawing of another embodiment of low pressure band gap reference generating circuit provided by the invention.As shown in Figure 6, this embodiment further limits the current mirror module among Fig. 2 embodiment, and this current mirror module comprises: the first FET MP1, the second FET MP2, the 3rd FET MP3;

MP1, MP2 and MP3 are the PMOS FET;

The source electrode of MP1, MP2 and MP3 all links to each other, as the voltage input end of current mirror module;

The grid of MP1, MP2 and MP3 all links to each other, as the control end of current mirror module;

The drain electrode of MP1 is as No. two current output terminals of current mirror module;

The drain electrode of MP2 is as the current input terminal of current mirror module, and the drain electrode of MP3 is the current output terminal of current mirror module.

Among Fig. 6, current mirror module is by three PMOS FETs, and promptly MP1, MP2 and MP3 constitute; The source electrode of these three FETs all links to each other, and grid also all links to each other, and has only the connection of drain electrode to have nothing in common with each other; Like this, MP1 and MP2 have just constituted a current mirror, and MP2 and MP3 have also constituted a current mirror; The drain electrode of MP2 is as the current input terminal of current mirror module among Fig. 1 and Fig. 2; The drain electrode of MP3 is as the current output terminal of current mirror module among Fig. 1 and Fig. 2, and the drain electrode of MP1 is as No. two current output terminals of current mirror module among Fig. 2, and the grid of MP1, MP2 and MP3 just becomes the control end of current mirror module shown in Figure 2.Therefore, the drain current of MP1, MP2 and MP3 is identical, is above-mentioned I with positive temperature coefficient (PTC) _PTAT

Only need be set to n the form that the bipolar transistor identical with Q2 is parallelly connected by Q1 among Fig. 6; The emitter current density that can accurately guarantee Q2 is n times of Q1; Like this, the present invention just can reduce the difficulty that parameter n is set through MP1 being set and MP2 sets up current mirror module; Improve the precision that is provided with of n, improve accuracy of the present invention.

Certainly, the n method doubly that the emitter current density of Q2 is set to Q1 also has a lot, repeats no more at this.

Among Fig. 6; MP1 also uses as the negative feedback of big gain operational amplifier; If when promptly the voltage of the positive input of big gain operational amplifier and negative input had had difference, its output promptly changed, thereby the drain voltage of MP1 is changed; And the drain voltage that MP1 has changed is linked into the negative input of gain operational amplifier greatly, the voltage of its negative input is reverted to the voltage of positive input equate.

In addition, MP1 is also through constituting current mirror with MP2, thereby electric current is provided for Q2.

This shows that the present invention has the following advantages:

(1) among the present invention; Because positive temperature rate current generating module can produce the electric current with positive temperature coefficient (PTC); This electric current is connected to the current input terminal of current mirror module, can obtains onesize and output current direction at the current output terminal of current mirror module, like this; After R2 and the Q3 series connection again with the circuit of R3 parallel connection owing to link to each other with the current output terminal of current mirror module, the electric current I that its input current is promptly produced with positive temperature rate current generating module _PTATIdentical, and, though the electric current that flows through R2 compares I through shunting _PTATSmaller, but also have positive temperature coefficient (PTC), thereby the voltage at R2 two ends just has positive temperature coefficient (PTC); According to transistor working principle, the base stage of bipolar transistor Q3 and the voltage V between the emitter _BE3Has negative temperature coefficient; The resistance of R2 also satisfies does not change the voltage at R2 two ends and the base stage of Q3 and the voltage sum between the emitter with variation of temperature; Therefore; The voltage at R3 two ends, be that the output voltage of this circuit has not just changed with variation of temperature yet; Be lower than at the supply voltage that the voltage input end of current mirror module inserts under 1.5 volts the situation, output voltage of the present invention just is the bandgap voltage reference that meets the zero-temperature coefficient condition.

(2) under the minimum supply voltage that is operated in 0.95V of the present invention, produce the benchmark output voltage of 0.75V, with respect to prior art, the present invention has had significant reduction to the requirement of supply voltage.

(3) output voltage of low pressure band gap reference generating circuit provided by the invention; Near normal temperature, can realize zero-temperature coefficient; In the temperature range between 233.15 Kelvin to 358.15 Kelvins, the temperature coefficient of output voltage is about 8ppm/ ℃, can think the zero-temperature coefficient condition that meets.

The above is merely preferred embodiment of the present invention, and is in order to restriction the present invention, not all within spirit of the present invention and principle, any modification of being done, is equal to replacement, improvement etc., all should be included within protection scope of the present invention.

Claims (6)

1. low pressure band gap reference generating circuit is characterized in that this circuit comprises: current mirror module, positive temperature rate current generating module, No. two resistance R 2, the 3rd transistor Q3, No. three resistance R 3, wherein,

Said current mirror module comprises: voltage input end, current input terminal and current output terminal;

Said positive temperature rate current generating module has No. seven ends and No. eight ends, and its No. seven end links to each other with the current input terminal of said current mirror module; Said positive temperature rate current generating module is used to produce the electric current with positive temperature coefficient (PTC);

R2 has No. three ends and No. four ends, and its No. three end links to each other with the current output terminal of current mirror module;

Q3 is a bipolar transistor; The emitter of Q3 links to each other with No. four ends of R2; The resistance of R2 satisfies does not change the voltage at R2 two ends and the base stage of Q3 and the voltage sum between the emitter with variation of temperature;

R3 has No. five ends and No. six ends; No. five ends of R3 link to each other with No. three ends of R2;

The voltage input end of said current mirror module is as the supply voltage input end; No. six ends of No. eight ends of said positive temperature rate current generating module, the base stage of Q3 and collector, R3 all are connected with the ground end; Voltage between said supply voltage input end and the ground end is lower than 1.5 volts; The voltage at R3 two ends is the reference voltage of output.

2. circuit according to claim 1 is characterized in that, said current mirror module further has control end and No. two current output terminals;

Said positive temperature rate current generating module comprises: big gain operational amplifier, the first transistor Q1, transistor seconds Q2, a resistance R 1 that has an end and hold for No. two; Wherein, Q1 and Q2 are bipolar transistor; The end of R1 links to each other with the emitter of Q1; No. two ends of R1 link to each other with the positive input of big gain operational amplifier and the current input terminal of current mirror module respectively; The emitter of Q2 links to each other with the negative input of big gain operational amplifier and No. two current output terminals of current mirror module respectively; The emitter current density of Q2 be Q1 emitter current density n doubly, n is the natural number greater than 1; The output of said big gain operational amplifier links to each other with the control end of said current mirror module, is used to make the electric current of No. two current output terminals of said current mirror module to equal the electric current of its current input terminal; The base stage of the base stage of Q1 and collector, Q2 all is connected with the ground end with collector.

3. circuit according to claim 2 is characterized in that, the resistance of R2 satisfies makes the voltage at R2 two ends and base stage and the voltage sum between the emitter of Q3 with the method that variation of temperature changes not be: the base stage of Q3 and the voltage V between the emitter _BE3, Q1 and Q2 thermoelectrical potential V _T, satisfy relational expression between absolute temperature T and R1, R2, the n:

Wherein,

Be V _BE3T is asked the resulting local derviation value of local derviation.

4. circuit according to claim 3 is characterized in that the voltage at R3 two ends does

$V_{\mathrm{BG}}=\frac{R_3}{R_2+R_3}(V_{\mathrm{BE}3}+\frac{V_T{R}_2}{R_1}\ln n).$

5. circuit according to claim 2 is characterized in that, said current mirror module comprises: the first FET MP1, the second FET MP2, the 3rd FET MP3;

MP1, MP2 and MP3 are the PMOS FET;

The source electrode of MP1, MP2 and MP3 all links to each other, as the voltage input end of said current mirror module;

The grid of MP1, MP2 and MP3 all links to each other, as the control end of said current mirror module;

The drain electrode of MP1 is as No. two current output terminals of said current mirror module;

The drain electrode of MP2 is as the current input terminal of said current mirror module, and the drain electrode of MP3 is the current output terminal of said current mirror module.

6. according to claim 1,2,3,4 or 5 described circuit, it is characterized in that T is between 233.15 Kelvin to 358.15 Kelvins.

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