Voltage reference circuit with micro power consumption
Technical field
The present invention relates to a kind of voltage reference circuit, particularly voltage reference circuit with micro power consumption.
Background technology
With reference to Fig. 2, document " a kind of design [J] of subthreshold type bootstrapping bandgap voltage reference; Chinese integrated circuit; 2008,109, p51-54 " discloses a kind of voltage reference circuit, this circuit is by enhancement mode PMOS transistor M1, enhancement mode PMOS transistor M2, enhancement mode PMOS transistor M3, enhancement mode nmos pass transistor M4, enhancement mode nmos pass transistor M5, enhancement mode nmos pass transistor M6, enhancement mode nmos pass transistor M7, positive-negative-positive triode Q1, resistance R 1, resistance R 2, resistance R 3 are formed.The source electrode of enhancement mode PMOS transistor M1, enhancement mode PMOS transistor M2, enhancement mode PMOS transistor M3 connects positive supply VDD, and grid connects together.The drain electrode of enhancement mode PMOS transistor M1 connects the upper end of resistance R 1, and the lower end of resistance R 1 connects the drain electrode of enhancement mode nmos pass transistor M4, and the grid of enhancement mode nmos pass transistor M4 is connected to the upper end of resistance R 1, and source electrode is connected to negative supply VSS.Grid and the drain electrode of enhancement mode PMOS transistor M2 link together, and drain electrode connects the drain electrode of enhancement mode nmos pass transistor M5.The grid of enhancement mode nmos pass transistor M5 is connected to the lower end of resistance R 1, and the source electrode of enhancement mode nmos pass transistor M5 is connected to negative supply VSS.The drain electrode of enhancement mode PMOS transistor M3 is connected with an end of resistance R 2, and the other end of resistance R 2 connects the emitter of positive-negative-positive triode Q1, and the base stage of positive-negative-positive triode Q1 and collector link together and be connected to negative supply VSS.The last termination positive supply VDD of resistance R 3, the drain electrode of following termination enhancement mode nmos pass transistor M7, grid and the drain electrode of enhancement mode nmos pass transistor M7 link together, and source electrode connects negative supply VSS.The drain electrode of enhancement mode nmos pass transistor M6 connects positive supply VDD, and grid connects the lower end of resistance R 3, and source electrode is connected to the upper end of resistance R 1.The upper end of resistance R 2 is the exit point of voltage reference.The transistorized substrate of all enhancement mode PMOS all is connected to positive supply VDD, and the substrate of all enhancement mode nmos pass transistors all is connected to negative supply VSS.
Enhancement mode PMOS transistor M1 and enhancement mode PMOS transistor M2 all are operated in the saturation region, and its breadth length ratio can be made as (W/L)
1: (W/L)
2=P: 1.Enhancement mode nmos pass transistor M4 and enhancement mode nmos pass transistor M5 are operated in sub-threshold region, and its breadth length ratio can be made as (W/L)
5: (W/L)
4=N: 1.Resistance R 1 both end voltage V
R1Provide by (1) formula:
V
R1=V
GS4-V
GS5 (1)
V in the formula
GS4The gate source voltage of expression enhancement mode nmos pass transistor M4, V
GS5The gate source voltage of expression enhancement mode nmos pass transistor M5.
Because enhancement mode nmos pass transistor M4 and enhancement mode nmos pass transistor M5 all are operated in sub-threshold region, so the gate source voltage of enhancement mode nmos pass transistor M4 and enhancement mode nmos pass transistor M5 uses (2) formula and (3) formula to represent respectively:
I in the formula
4, I
5Be respectively the drain current of enhancement mode nmos pass transistor M4, enhancement mode nmos pass transistor M5, V
TBe thermal voltage, n is the subthreshold value factor.Because I
4: I
5=P: 1 (enhancement mode PMOS transistor M1 and enhancement mode PMOS transistor M2 form current mirror), (W/L)
5: (W/L)
4=N: 1, can get resistance R 1 both end voltage V by (1) formula, (2) formula, (3) formula simultaneous
R1Satisfy the condition of (4) formula:
V
R1=nV
Tln(N·P) (4)
Electric current I on the resistance R 1
R1Satisfy the condition of (5) formula:
This electric current after enhancement mode PMOS transistor M2 and enhancement mode PMOS transistor M3 current mirror coupled, the electric current I among the enhancement mode PMOS transistor M3
3Satisfy the condition of (6) formula:
So, voltage reference V
RefSatisfy the condition of (7) formula:
V wherein
RefThe output voltage of expression voltage reference, V
BelThe base-emitter voltage of expression triode Q1.
Enhancement mode nmos pass transistor M6, enhancement mode nmos pass transistor M7 and resistance R 3 are formed start-up circuit.Before the circuit start, the electric current of enhancement mode PMOS transistor M1, enhancement mode PMOS transistor M2 and enhancement mode PMOS transistor M3 is zero, and the last terminal voltage of resistance R 1 is negative supply VSS.During circuit start, the branch road that resistance R 3 and enhancement mode nmos pass transistor M7 form provides current potential for the grid of enhancement mode nmos pass transistor M6, because the source potential of enhancement mode nmos pass transistor M6 is negative supply VSS, enhancement mode nmos pass transistor M6 conducting, provide noble potential, enhancement mode nmos pass transistor M4 conducting for the grid of enhancement mode nmos pass transistor M4.There has been current potential the upper end of resistance R 1 after the circuit balancing, causes the threshold voltage of the gate source voltage of enhancement mode nmos pass transistor M6 less than enhancement mode nmos pass transistor M6, enhancement mode nmos pass transistor M6 by, start-up course is finished, start-up circuit is ineffective.
By reasonably being worth for the relative parameters setting in (7) formula, can make V
RefAcquisition is near zero-temperature coefficient, but the shortcoming of this circuit is to need start-up circuit, and complex structure, and will consume the electric current of about 4.5uA, start-up circuit current sinking still after startup is finished can not well satisfy requirement simple in structure, little power consumption.
Summary of the invention
In order to overcome prior art voltage reference circuit power consumption height, baroque deficiency, the invention provides a kind of voltage reference circuit with micro power consumption, this circuit does not need start-up circuit, and depletion type nmos transistor M2 is at V
GS2Be conducting under=0 the situation, constant electric current is provided, this electric current enhancement mode nmos pass transistor M5 that flows through produces constant gate source voltage on enhancement mode nmos pass transistor M5, and this voltage is voltage reference.The main effect of enhancement mode nmos pass transistor M3 is electric current to be provided for when circuit start right half branch road, produces the grid voltage that enhancement mode nmos pass transistor M5 conducting needs.Circuitry consumes utmost point low current can satisfy the requirement of low power dissipation design.
The technical solution adopted for the present invention to solve the technical problems: a kind of voltage reference circuit with micro power consumption, enhancement mode nmos pass transistor M5, resistance R 2, it is characterized in that, also comprise depletion type nmos transistor M2, enhancement mode nmos pass transistor M3, the drain electrode of depletion type nmos transistor M2 connects positive supply VDD, and grid connects source electrode, source electrode connects the drain electrode of enhancement mode nmos pass transistor M5, and substrate connects source electrode.The grid of enhancement mode nmos pass transistor M5 connects the upper end of resistance R 2, and source electrode connects power supply negative terminal VSS, and substrate connects source electrode.The drain electrode of enhancement mode nmos pass transistor M3 connects positive supply VDD, and grid connects the grid of depletion type nmos transistor M2, and source electrode connects the upper end of resistance R 2, and substrate connects source electrode.The lower end of resistance R 2 connects negative supply VSS.Resistance R 2 upper ends are the exit point of voltage reference.
The invention has the beneficial effects as follows: 1) circuit power consumption is extremely low.This circuit utilizes depletion type nmos transistor at V
GSThe characteristic of steady current can be provided under=0 the situation, provide the steady current of nA level, produce stable voltage reference at the grid of enhancement mode nmos pass transistor M5 by depletion type nmos transistor M2.And general circuit can not produce the steady current of nA level, also just can not obtain the extremely low voltage reference circuit of power consumption.The about 850nA electric current of circuitry consumes of the present invention, and the about 4.5uA electric current of the circuitry consumes of prior art, circuit power consumption of the present invention has only 19% of prior art; 2) save chip area.This circuit structure is simple, does not need start-up circuit, can obviously reduce number of transistors.When circuit powers on, because depletion type NMOS is at V
GSBut yet conducting under=0 the situation, circuit do not need other start-up circuit can produce voltage reference, and the circuit of prior art must add start-up circuit, otherwise circuit can not reach matching point.
Below in conjunction with drawings and Examples the present invention is elaborated.
Description of drawings
Fig. 1 is the circuit diagram of the embodiment of the invention 1.
Fig. 2 is the circuit diagram of prior art voltage reference circuit.
Embodiment
Embodiment 1: with reference to Fig. 1, the present embodiment voltage reference circuit is made up of a depletion type nmos transistor M2, enhancement mode nmos pass transistor M5, enhancement mode nmos pass transistor M3 and resistance R 2.The drain electrode of depletion type nmos transistor M2 connects positive supply VDD, and grid connects source electrode, and source electrode connects the drain electrode of enhancement mode nmos pass transistor M5, and substrate connects source electrode.The grid of enhancement mode nmos pass transistor M5 connects the upper end of resistance R 2, and source electrode connects negative supply VSS, and substrate connects source electrode.The drain electrode of enhancement mode nmos pass transistor M3 connects positive supply VDD, and grid connects the grid of depletion type nmos transistor M2, and source electrode connects the upper end of resistance R 2, and substrate connects source electrode.The lower end of resistance R 2 connects negative supply VSS.Resistance R 2 upper ends are the exit point of voltage reference.
The source electrode of depletion type nmos transistor M2, enhancement mode nmos pass transistor M5 and enhancement mode nmos pass transistor M3 is connected with substrate, reducing bulk effect, thereby reduces the threshold voltage of metal-oxide-semiconductor.This voltage reference circuit does not need additional start-up circuit.When circuit powered on, enhancement mode nmos pass transistor M5 was in cut-off state, and depletion type nmos transistor M2 is at V
GS2But also conducting under=0 the situation, GuN1Chu is a noble potential, enhancement mode nmos pass transistor M3 conducting this moment, electric current by positive supply VDD through enhancement mode nmos pass transistor M3, resistance R 2 to negative supply VSS, on resistance R 2, produce pressure drop, V
RefBegin to rise from zero potential, also conducting thereupon of enhancement mode nmos pass transistor M5, circuit finally reaches stable duty.Exportable stable, the voltage reference V of temperature influence not of circuit
Ref
For depletion type nmos transistor M2, its saturated drain current I flows through
2Satisfy the condition of (11) formula:
I
2=K
2(V
GS2-V
TD)
2 (11)
K in the formula
2The conductivity of expression depletion type nmos transistor M2, V
GS2The grid of expression depletion type nmos transistor M2 and the voltage between the source electrode, V
TDThe threshold voltage of expression depletion type nmos transistor M2.The saturated drain current I of enhancement mode nmos pass transistor M5
5Satisfy the condition of (12) formula:
I
5=K
5(V
GS5-V
TE)
2 (12)
K in the formula
5The conductivity of expression enhancement mode nmos pass transistor M5, V
GS5The grid of expression enhancement mode nmos pass transistor M5 and the voltage between the source electrode, V
TEThe threshold voltage of expression enhancement mode nmos pass transistor M5.
Because I
2=I
5, V
GS2=0, so can get voltage reference V by (11) formula and (12) formula simultaneous
Ref=V
GS5Satisfy the condition of (13) formula:
By (13) formula as can be seen, the temperature characterisitic of voltage reference only is subjected to depletion type nmos transistor M2 and two transistorized parameter influences of enhancement mode nmos pass transistor M5, K
2, K
5, V
TD, V
TEAll be the function of temperature, V
TD, V
TEBy the process conditions decision, K is set
2And K
5Value can obtain the voltage reference of approximate zero temperature coefficient.V
RefSize directly by V
TD, V
TEDetermine.The V that in different technology, obtains
RefValue meeting change, this is because the V of different process correspondence
TD, V
TEAlso different.Depletion type nmos transistor M2 links to each other with substrate with the source electrode of enhancement mode nmos pass transistor M5, can reduce V
TD, V
TEThereby, obtain littler voltage reference.
Obtaining voltage reference V
RefThe time, also determined the electric current of right half branch road of circuit, the electric current I of enhancement mode nmos pass transistor M3
3Satisfy the condition of (14) formula:
Simultaneously by the saturated drain current formula of nmos pass transistor I as can be known
3Satisfy the condition of (15) formula:
I
3=K
3(V
GS3-V
TE)
2=K
3(V
N1-V
ref-V
TE)
2 (15)
K wherein
3The conductivity of expression enhancement mode nmos pass transistor M3, V
GS3The grid of expression enhancement mode nmos pass transistor M3 and the voltage between the source electrode, V
TEThe threshold voltage of expression enhancement mode nmos pass transistor M3.
The electric current of enhancement mode nmos pass transistor M3 is by V
RefDetermine with R2, work as V as can be known by (16) formula
RefAfter determining with R2, V
N1And K
3Inversely proportional relation.The precondition that obtains (11) formula is that depletion type nmos transistor M2 is in the operate in saturation district, also is the condition that three terminal voltages of depletion type nmos transistor M2 should satisfy (16) formula:
V
GS2-V
TD<VDD-V
N1 (16)
V
N1Must satisfy (16) formula, otherwise can cause depletion type nmos transistor M2 to be operated in linear zone, (13) formula is just incorrect to the derivation of voltage reference at this moment.So in circuit design, K
3Be provided with and must guarantee V
N1Current potential satisfies (16) formula.