TW200803131A - Generation circuit of reference voltage - Google Patents

Abstract

The present invention is a generation circuit of reference voltage to supply a reference voltage almost independent of the temperature variation, which comprises: a resistor connected to the output end of the generation circuit of reference voltage and a bipolar transistor; a first current source supplying a first current having a positive temperature coefficient to the resistor; a second current source supplying a second current having a negative temperature coefficient to the resistor. By adjusting the first and second currents and the resistor, the required output reference voltage can be obtained.

Description

200803131 » IX. Description of the Invention: [Technical Field] The present invention relates to a reference voltage generating circuit which is a reference voltage generating circuit capable of adjusting an output voltage as needed and having almost no temperature change. 5 [Prior Art] In electronic electricity, it is often necessary to supply a reference voltage generator—a stable reference voltage. 1 is a conventional reference voltage generator 10, which includes a bandgap reference voltage circuit 12 for supplying an irrelevant temperature change voltage Vbg, and a resistor connected in series between the reference voltage Vref and the ground GND, when the PM0S is electrically When the crystal 16 operates in the saturation region, the operational amplifier 14 forms a negative feedback through the resistor R1, so the voltage Vfb is equal to the voltage Vbg'. Therefore, the magnitude of the reference voltage vref depends on the resistors R1 and R2 and the voltage Vbg. In the reference voltage generator 1 ,, the magnitude of the reference voltage Vref can reach (VDD - Vsd), where VDD is the supply voltage and Vsd is the voltage difference between the source 15 and the drain of the PMOS transistor 16, but The source of the PM0S transistor 16 is connected to the power supply voltage VDD ' because of the following phenomenon between the source and the gate. Therefore, when there is noise in the power supply voltage, the signal Vg on the gate of the PM0 transistor 16 is also Under the influence of noise, the PM0S transistor 16 enters the triode region, thereby affecting the reference voltage Vref. In other words, the reference voltage generator 10 has a poor Power Supply Rejection Ratio (PSRR). In order to improve the PSRR capability of the reference voltage generator 10, the reference voltage generator 20 shown in FIG. 2 generally replaces the PMOS transistor 16 with the NMOS transistor 22, and the power supply voltage VDD is connected to the immersed transistor of the NM0S transistor 22. Therefore, the noise in the power supply voltage vdd does not affect the signal Vg on the gate of the NMOS transistor 22, so that the reference voltage generator 20 has a better PSRR. However, since the signal Vg has a follow-up relationship with the reference voltage Vref, Vg=Vref+Vth, where Vth is the threshold voltage of the NM0S transistor 22, therefore, if the NMOS transistor 22 is to be maintained in the saturation region, the reference voltage

Vref must be smaller than (face-Vsd-Vth). If the minimum operating voltage of the voltage VDD is 3V and the required reference voltage Vref is 2·5ν, the reference voltage generator is not applicable. 3 is a circuit designed according to the reference voltage generator 10 using a computer software, wherein the bandgap reference voltage circuit 30 corresponds to the bandgap reference voltage circuit 12 in FIG. 1, and the proportional voltage generator 32 corresponds to the operational amplifier 14, PM0S in FIG. Amplifier circuit composed of transistor 16, resistors R1 and R2, and circuits 34 and 36 are output buffers. 15 is a PSRR simulation diagram of the output voltage Vbg of the band gap reference voltage circuit 30 at different frequencies, wherein the χ axis frequency and the γ axis voltage 诎 value. Figure 5 is the proportional voltage generated in Figure 3! The output voltage of 32 is the same as that of the different frequency linings, in which the X-axis frequency, the γ-axis voltage DB value, and the curve 38-series voltage vim' curve 39-series voltage job. In Fig. 6, the modulo _ of the reference voltage vrt output from the buffer material is taken out, wherein the χ-axis frequency and the DB value of the γ-axis voltage. Figure 7 is the output buffer in Figure 3.

The output of the reference voltage is Sonic's PSRR simulation plot, where the χ axis is the frequency, and the γ axis is the DB value of your argon. <<4 Display Energy Gap Parameter 6 20 200803131 • 1 The DB value of the voltage Vbg outputted by the test voltage circuit 30 is at most about -28, and the voltage Vbg is amplified by the proportional voltage generator 32 and the voltages VRT1 and VRM are amplified. The maximum is about -4 and -6, as shown in FIG. 5, therefore, the PSRR of the bandgap reference voltage circuit 30 produces a good ||32, so if it can be directly provided by the 5-band reference voltage circuit 3G The voltage and the Nab should be able to get the reference voltages VRT and 雠 with good and good. However, although the bandgap reference voltage circuit has the advantages of a better PSRR and a stable voltage that can provide an irrelevant temperature, the conventional bandgap reference voltage circuit uses a bipolar transistor to generate a voltage, even if appropriate. Designing a bipolar transistor can provide a voltage that is independent of temperature changes. A conventional gap-free reference voltage circuit can only supply a voltage of about 1.23V. — Therefore, a reference voltage generating circuit that can adjust the output voltage as needed is what it is. SUMMARY OF THE INVENTION The purpose of the present invention is to provide a reference voltage generating circuit for adjusting the output voltage as needed. According to the present invention, the reference voltage generating circuit includes a bipolar transistor connected to a body, and is electrically coupled between the output of the reference generating circuit and the bipolar transistor. Supplying - a first current having a positive temperature coefficient to the resistor, and - a second current source, supplying a second having a negative temperature coefficient: flowing to the resistor. 7 200803131 Since the present invention increases the second current having a negative temperature coefficient to the resistor, the present invention can obtain a reference voltage that is required and hardly related to temperature changes by adjusting the first and second currents and resistances. [Embodiment] FIG. 8 is an embodiment of the present invention. In the reference voltage generating circuit 4, the self-biasing circuit 401 supplies a current Iptat 'PM0S transistor 402 and a bipolar transistor in series with the power supply voltage VDD and the ground GND. The pm 〇S transistor 404, the resistor R3 and the bipolar transistor Q4 are connected in series between the power supply voltage vdd and the ground GND. The PMOS transistor 10 414 is connected to a capacitor and connected to the output of the reference voltage generating circuit 40 for stabilization. The reference voltage Vref, wherein the PM0S transistor 402 and the 404 mirror current Iptat generate currents 12 and II, respectively. In the self-biasing circuit 401, the PMOS transistors 406 and 408 form two cascode current mirrors with the NMOS transistors 410 and 412, and the bipolar transistor Q1 is connected to the NM0S transistor 412 via the resistor R1. The bipolar transistor Q2 u is connected to the NM0S transistor 410, and the NM0S transistors 410 and 412 form a current mirror, so the potentials of the nodes A and B are equal, so the current through the resistor w can be obtained.

Iptat=(Veb2-Vebl)/Rl Equation 1 20 where Veb is the differential pressure between the emitter and the base of the bipolar transistor qi, and Veb2 is the voltage between the emitter and the base of the bipolar transistor Q2. difference. Bipolar transistor Q1 8 200803131

And Q2 are each connected to a diode, according to the diode current formula 15 of the PNP bipolar crystal

Id=IseffxeVeb/nVt

Iseff=AREA&gt;&lt;Is Equation 3

Vt=kxT/q Equation 4 where ' Iseff is the saturation current' The PN of the AREA bipolar transistor is the saturation current per unit area of the bipolar transistor, Vt is the 埶n voltage, and the k-system is the Boltzman constant. q is a charge of 1 electron, and τ is a constant between 1 and 2. According to formula 2, the product can be obtained.

Veb2-Vebl = nVtxln(Iseffl/Iseff2) where Iseffl is the saturation current of transistor Q1 and Iseff2 is the saturation current of transistor Q2. Substituting formulas 3 and 4 into formula 5

Veb2-Vebl=[nxkxTx 1 n(AREA1 /AREA2)]/q Equation 6 200803131 where 'AREA1 is the size of bipolar transistor Q1, the size of ARea2 bipolar transistor Q2, the parameter of two bipolar transistors Is Are the same. Substituting Equation 6 into Equation 1 gives current 5

Iptat=[nxkxTxln(AREAl/AREA2)]/(qxRl) Equation 7 where n, k, ln(AREAl/AREA2), q and R1 are fixed values, therefore, when the absolute hunger T rises, the current iptat will As it increases, the current iptat has a positive 10 degree coefficient. On the other hand, the PMOS transistors 404 and 408 are connected to form a current mirror, and the mirror current Iptat generates a current II to a resistor R3, wherein the size ratio of the PM〇s transistors 4〇4 to 4〇8 is N:1. The current iLlptat, the PM0S transistors 402 and 408 are connected to a current mirror, and the current η is generated by the mirror current Iptat, wherein the size ratio of the pM〇s 15 transistors 402 and 408 is Μ: 1, so the current i2=MxIptat, The resistor R2 is connected between the emitter and the base of the bipolar transistor Q3, and the current on the resistor is

Intat=Veb3/R2, ^. Equation 8 20 wherein Veb3 is the pressure difference between the emitter and base of the bipolar transistor q3. According to the characteristics of the bipolar transistor, the voltage between the emitter and the base of the PNP bipolar transistor Q3 is 200803131. The difference Veb3 decreases with temperature rise. In other words, the voltage Veb3 has a negative temperature coefficient, so the current Intat also has a negative temperature coefficient. . According to the current formula of the bipolar transistor, the base current of the bipolar transistor q3 can be known.

Ib=(I2-Intat)/(/3+l) Equation 9 Substituting Equation 8 into Equation 9

Ib=Mx Iptat/(β +1 )-Veb3/ [ (/3 +1 )xR2 ] Equation 10 where is the current gain of the /5-system bipolar transistor Q3. Reference voltage generated by the reference voltage generating circuit

Vref=VR3+Veb4 15 where VR3 is the voltage across the resistor R3 and the voltage difference between the emitter and the base of the veb4 bipolar transistor q4. Equation 12 VR3=ItotalxR3 and the current through resistor R3 11 20 200803131 I total=11+Intat+ Ib=Nx Iptat+ Intat+ lb Equation 13 Substituting Equations 7, 8 and 10 into Equation 13

nxkxTxlnC

Itotal = Nx AREA1AREA2 qxRl

Veb3 formula 14

MxIptat__Jeb3^ + ~^+T_ (^ + 1)xR2 Substituting the formulas 12 and 14 into the formula 11 gives the reference voltage nxkxTxlnC^M)

Vref = Veb4 + [N x--4EEA2 ( Veb3

QxRl R2 formula 15

+ Mxlptat Veb3 β + l C^ + l)xR2J As can be seen from Equation 15, the reference voltage Vref can be adjusted by adjusting the resistance, the ridge and the rib and the size ratio. Figure 9 shows a circuit designed using computer software, wherein circuit 5 is designed in accordance with reference voltage generating circuit 40 of Figure 815, and circuits 52 and 54 are output buffers. 10 and 11 are simulation diagrams made according to the circuit of Fig. 9. Fig. 1〇 The top of the ^^1212 0303131 shows the curve 6G is the simulation of the reference voltage output from the circuit 5G of Fig. 9 in different fields, Kawasaki _ (four) is · 5Q round (four) simulation of reference electricity at different temperatures The lowermost curve 64 of the figure is the curve 6. The _ line obtained after subtracting the curve 62, wherein the χ axis represents temperature and the γ axis represents lag. As can be seen from the simulation of Figure 10, the reference voltage is about 1.5V and the reference voltage is about 2.4V, both of which are higher than the known 123V, and are almost immune to temperature. In the upper curve 7 in FIG. 11 (the PSRR simulation diagram of the reference voltage side outputted by the H-system 50 at different frequencies, the lower curve 72 is the pSRR simulation diagram of the reference voltage VRT1 outputted by the circuit 5〇 at different frequencies, Among them, the χ axis is the frequency, and the γ axis is the DB value of the voltage. As can be seen from the figure η, the reference voltage surface and the deleted dina are at least -28 dB. Therefore, the 'this _ reference voltage generating circuit not only has a good PSRR. Capability, and can adjust the reference voltage that is transmitted (4) almost irrelevant to temperature changes. 15 [Simplified Schematic] FIG. 1 is a conventional reference voltage generator; FIG. 2 is another conventional reference voltage generator; Figure 3 shows the circuit designed with computer software; Figure 4 is the simulation diagram of the output voltage (4) of the bandgap reference voltage circuit 3 in the ® 3; Figure 5 is the voltage VRT1 output by the proportional voltage generator 32 in Figure 3. Figure 13 is a PSRR simulation diagram of the reference voltage VRT in Figure 3; Figure 7 is a PSRR simulation diagram of the reference voltage VRB in Figure 3; Figure 8 is an embodiment of the present invention; a circuit designed using computer software; Figure 1 0 is a simulation diagram of the reference voltages VRB and VRT at different temperatures in FIG. 9; and FIG. 11 is a psRR diagram of the reference voltages VRB and VRT at different frequencies in FIG. 9. 10 [Remarks of main components] 10 Reference voltage Generator 12 Bandgap Reference Voltage Circuit 14 Operational Amplifier 15 16 PM0S Transistor 20 Reference Voltage Generator 22 Transistor 30 Bandgap Reference Voltage Circuit 32 Proportional Voltage Generator 20 34 Output Buffer 36 Output Buffer 200803131 38 Curve of Voltage VRT1 39 Voltage VRB1 curve 40 Reference voltage generation circuit 401 Self-biasing circuit 5 402 PMOS transistor 404 PMOS transistor 406 PMOS transistor 408 PMOS transistor 410 NM0S transistor ί 412 MOS transistor 414 PMOS transistor 50 reference voltage generation circuit 52 Output Buffer 54 Output Buffer is 60 Curve of Reference Voltage VRB1 - 62 Curve of Reference Voltage VRT1 Curve of Curve 60 after subtraction of Curve 62 Curve of Reference Voltage VRB1 72 Curve of Reference Voltage VRT1

Claims (1)

200803131 X. Patent application scope: “The test voltage generation circuit, (4) Supply – the reference voltage of the domain temperature change at the output terminal, the reference voltage generation circuit includes: 5 bipolar transistor 'connected into a diode| Connected between the wheel end and the bipolar transistor; 'supply—the first current having a positive temperature coefficient to the resistive element; and the first current source, supplying a second current having a negative temperature coefficient Resistive component. The reference voltage generating circuit of Wei 1 is the first current source of the first bipolar transistor, which is connected to a diode, and the second bipolar transistor is irradiated. a first differential pressure is formed between the pole and the base; a second bipolar transistor is connected to form a diode, and a second differential pressure is formed between the emitter and the base of the third bipolar transistor; a second resistive element, generating a third current having the positive temperature coefficient according to a difference between the first and second differential pressures; and a current mirror mirroring the third current to generate the first Current. 3. If the request is 丨a reference voltage generating circuit, wherein the second current source comprises: a second bipolar transistor having an emitter, a collector and a base connection 20; the resistive element; and a second resistive element connected The second current is generated between the emitter and the base of the second bipolar transistor according to a voltage difference between the emitter and the base of the second bipolar transistor.