CN102622031A - Low-voltage high-precision band-gap reference voltage source - Google Patents

Abstract

The invention relates to the technical field of BJT and CMOS transistor circuits, in particular to a low-voltage high-precision bandgap reference voltage source. The voltage source includes a first current generating circuit, a second current generating circuit, a third current generating circuit and a current superposition circuit; the first current generating circuit is used to generate a current that is directly proportional to the temperature change; the second current A generating circuit for generating a current with a negative first-order temperature coefficient and a positive second-order temperature coefficient; a third current generating circuit for generating a current with a negative first-order temperature coefficient and a negative second-order temperature coefficient; The superposition circuit is used to superimpose the generated three currents, and the superimposed current provides the reference voltage required for output through the resistance. The invention improves the precision of the bandgap reference voltage source, enables the output reference voltage to be adjusted according to actual needs, and enables the entire bandgap reference voltage circuit to work normally at a lower power supply voltage.

Description

A low-voltage high-precision bandgap reference voltage source

technical field

The invention relates to the technical field of BJT and CMOS transistor circuits, in particular to a low-voltage high-precision bandgap reference voltage source.

Background technique

In the prior art, there is a traditional bandgap reference voltage source circuit as shown in Figure 1, which includes triode transistors Q1 and Q2, error amplifier OP, feedback resistors R1 and R2, and adjustment resistor R3; the emitters of transistors Q1 and Q2 The analog ground is AVSS, the two input terminals of the amplifier are connected to nodes A and B respectively, the output terminal is connected to V _OUT , and resistors R1 and R2 are connected at the same time. The working principle of the bandgap reference circuit shown in Figure 1 is as follows:

The amplifier OP works in deep negative feedback. The two input terminals are respectively connected to nodes A and B, so that the voltages of the two points are equal. The output terminal of the amplifier OP is connected to V _OUT . and the two currents of Q2 are equal, so as to obtain:

V _BE1 -V _BE2 =I ₂ R ₃ =V _T InN(1);

If the voltages of nodes A and B are not completely equal, the error amplifier OP compares the voltages of nodes A and B, and amplifies the difference ΔV to obtain ΔVmax, which causes the currents flowing through transistors Q1 and Q2 to vary in different degrees Change, the voltage drop of resistor R3 also changes accordingly, so that the voltages of node A and node B are approximately equal, and then the voltage value of the output voltage V _OUT tends to be constant as:

${\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; REF</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; BE</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; T</span>}}\mathrm{<span\; class="notranslate">\; ln</span>}\mathrm{<span\; class="notranslate">\; N</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\frac{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ,</span>$

The first-order temperature coefficient of the first term in formula (2) is -1.5mV/℃, and the second term V _T has a positive temperature coefficient of 0.086mV/℃. By properly selecting N and the ratio of resistors R2 and R3, a zero temperature coefficient can be obtained output voltage VREF.

The circuit shown in Figure 1 has the following two problems. First, V _REF is usually about 1.25V, which cannot be used in low-voltage circuits. Second, this method does not compensate the second-order temperature coefficient of V _BE , and its temperature coefficient is usually limited to several Ten ppm/°C.

In the prior art, there is also a bandgap circuit as shown in Figure 2. In this bandgap circuit, M1, M2 and M3 form a current mirror, and the amplifier OP1 is in a deep negative feedback state, so that the voltages of AB and AB are equal, which is V _BE , That is, the current flowing through R2 is V _BE /R2, which has a negative temperature coefficient, and the current passing through the resistor R1 is a current proportional to V _T. The sum of the two currents flows through M2 and is copied to I3, then the resistor R3 The voltage across is:

${\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; REF</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}}{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; BE</span>}}<span\; class="notranslate">\; +</span>\frac{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}}{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; T</span>}}\mathrm{<span\; class="notranslate">\; ln</span>}\mathrm{<span\; class="notranslate">\; N</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ;</span>$

Proper selection of N, R1, R2 and R3 can obtain the output voltage V _REF with zero temperature coefficient, and the temperature coefficient of the output voltage is independent of R3, that is, the output bandgap reference voltage can be adjusted.

However, the circuit shown in Figure 2 only has first-order temperature coefficient compensation and no second-order compensation, so the temperature coefficient is usually 10-20ppm/°C.

Contents of the invention

The purpose of the present invention is to provide a low-voltage high-precision bandgap reference voltage source, which effectively improves the accuracy of the bandgap reference voltage source and enables the output reference voltage to be adjusted according to actual needs.

The technical scheme that the present invention solves the problems of the technologies described above is as follows:

A low-voltage high-precision bandgap reference voltage source, including a first current generating circuit, a second current generating circuit, a third current generating circuit and a current superposition circuit;

The first current generating circuit is used to generate a current with a specific relationship with the temperature change, and the relationship between the current and the temperature in the first current generating circuit is: proportional to the temperature change;

The second current generating circuit is used to generate a current that has a specific relationship with temperature changes. The relationship between current and temperature in the second current generating circuit is: the first-order temperature coefficient is negative, and the second-order temperature coefficient is positive;

The third current generation circuit is used to generate a current with a specific relationship with temperature changes, the relationship between the current and temperature in the third current generation circuit is: the first-order temperature coefficient is negative, and the second-order temperature coefficient is negative;

The current superimposition circuit is used to superimpose the three currents generated by the first current generation circuit, the second current generation circuit and the third current generation circuit, and the superimposed current provides the output value through the adjustment resistor. The required reference voltage;

The current superimposition circuit uses the characteristics of the current temperature coefficient generated by the three-way current generating circuit to make the first-order and second-order temperature coefficients of the superimposed current zero by adjusting the ratio of the three-way current to generate the first-order and second-order Reference voltage with zero temperature coefficient.

In the above scheme, the first current generating circuit includes a triode Q1 and a triode Q2, a resistor R1, current mirror tubes M2 and M3, and an amplifier OP1; the emitter of the triode Q1 is connected to the collector of the current mirror tube M2 through a resistor R1, and the triode The emitter of Q2 is connected to the collector of the current mirror tube M3, the emitters of the current mirror tube M2 and the current mirror tube M3 are respectively connected to the power supply voltage V _DD , the collectors of the transistor Q1 and the transistor Q2 are respectively grounded; the two input terminals of the amplifier OP1 Respectively connect the node A between the resistor R1 and the current mirror tube M2 and the node B between the triode Q2 and the current mirror tube M3, the output terminals of the amplifier OP1 are respectively connected to the gates of the current mirror tube M2 and the current mirror tube M3, and the control The gate voltages of the current mirror tube M2 and the current mirror tube M3 form a feedback loop.

In the above solution, the second current generating circuit includes a current mirror tube M1, a load tube M11, a resistor R2, an amplifier OP21, a feedback tube M9, and a current mirror tube M5; the source of the current mirror tube M1 is connected to VDD, and the current mirror tube M1 The grid of the current mirror tube M2 and the grid of the current mirror tube M3 are connected, the drain of the current mirror tube M1 is connected to the positive input terminal of the amplifier OP21 and the drain and the grid of the load tube M11, and the load tube M11 is in a diode connection mode. The source of the load tube M11 and one end of the resistor R2 are commonly grounded, the other end of the resistor R2 is connected to the source of the feedback tube M9 and the negative input terminal of the amplifier OP21, the output terminal of the amplifier OP21 is connected to the gate of the feedback tube M9, and the drain of the feedback tube M9 The pole is connected to the gate and drain of the current mirror tube M5, the source of the current mirror tube M5 is connected to VDD, and is in a diode connection mode. The amplifier OP21 forms a feedback loop with the feedback tube M9, the resistor R2 and the load tube M11.

In the above scheme, the third current generating circuit includes a triode Q2, a resistor R3, an amplifier OP22, a feedback tube M10, and a current mirror tube M7; the positive input terminal of the amplifier OP22 is connected to the emitter of the triode Q2, and the negative input terminal of the amplifier OP22 is connected to The source of the feedback tube M10 and one end of the resistor R3, the other end of the resistor R3 is grounded, the output terminal of the amplifier OP22 is connected to the gate of the feedback tube M10, the drain of the feedback tube M10 is connected to the drain and the gate of the current mirror tube M7, The source of the current mirror tube M7 is connected to VDD and is in a diode connection mode. The amplifier OP22 forms a feedback loop with the feedback tube M10, the resistor R3 and the transistor Q2.

In the above scheme, the current superposition circuit includes a resistor R4, a current mirror tube M4, a current mirror tube M6 and a current mirror tube M8; the sources of the current mirror tube M4, the current mirror tube M6 and the current mirror tube M8 are connected to VDD, and the drains One end of the resistor R4 is connected, the grid is respectively connected to the grids of the current mirror tube M3, the current mirror tube M5 and the current mirror tube M7, and the other end of the resistor R4 is grounded.

In the above solution, the current mirror tubes M1 , M2 , M3 and M4 have the same width-to-length ratio and are connected by current mirrors.

In the above solution, the load tube M5 and the current mirror tube M6 have the same width-to-length ratio, and are connected by a current mirror.

In the above solution, the load tube M7 and the current mirror tube M8 have the same width-to-length ratio, and are connected by a current mirror.

Compared with prior art, the beneficial effect of the present invention is:

The bandgap reference voltage source circuit provided by the present invention adopts the method of superimposing three currents with different temperature characteristics, so that the first-order and second-order temperature coefficients of the superimposed current tend to zero, so that the temperature coefficient of the output reference voltage is far away. It is smaller than the temperature coefficient of the output voltage in the prior art, effectively improving the accuracy of the bandgap reference voltage source; and, the structure adopted by the bandgap reference circuit provided by the present invention enables the output reference voltage to be adjusted according to actual needs, and due to The amplifier can work normally in the low voltage circuit, therefore, the whole bandgap reference voltage circuit can work normally under the lower supply voltage.

Description of drawings

Fig. 1 is the circuit diagram of a kind of bandgap reference voltage source in the prior art;

Fig. 2 is the circuit diagram of another kind of bandgap reference voltage source in the prior art;

FIG. 3 is a circuit diagram of a bandgap reference voltage source provided by an embodiment of the present invention.

Detailed ways

The principles and features of the present invention are described below in conjunction with the accompanying drawings, and the examples given are only used to explain the present invention, and are not intended to limit the scope of the present invention.

As shown in FIG. 3 , an embodiment of the present invention provides a low-voltage high-precision bandgap reference voltage source, including a first current generating circuit, a second current generating circuit, a third current generating circuit, and a current superposition circuit;

The first current generating circuit is used to generate a current with a specific relationship with the temperature change, and the relationship between the current and the temperature is: proportional to the temperature change;

The second current generation circuit is used to generate a current with a specific relationship with temperature, the relationship between the current and temperature is: the first-order temperature coefficient is negative, and the second-order temperature coefficient is positive;

The third current generation circuit is used to generate a current with a specific relationship with temperature, the relationship between the current and temperature is: the first-order temperature coefficient is negative, and the second-order temperature coefficient is negative;

The current superposition circuit is used to superimpose the three currents generated by the above three current generation circuits, and the superimposed current provides the reference voltage required for output through the adjustment resistor;

In the above-mentioned four-part circuit, the current superposition circuit utilizes the characteristics of the current temperature coefficient generated by the three-way current generating circuit, and by adjusting the ratio of the three-way current, the first-order and second-order temperature coefficients of the superimposed current are zero, and the first-order and second-order temperature coefficients are generated. Reference voltage with zero step temperature coefficient.

Wherein, the first current generating circuit includes triode Q1 and triode Q2, resistor R1, current mirror tubes M2 and M3, and amplifier OP1; the emitter of triode Q1 is connected with the collector of current mirror tube M2 through resistor R1, and the emitter of triode Q2 Connect to the collector of the current mirror tube M3, the emitters of the current mirror tube M2 and the current mirror tube M3 are respectively connected to the power supply voltage V _DD , the collectors of the transistor Q1 and the transistor Q2 are respectively grounded; the two input terminals of the amplifier OP1 are respectively connected to the resistor R1 The node A between the current mirror tube M2 and the node B between the triode Q2 and the current mirror tube M3, the output terminals of the amplifier OP1 are respectively connected to the gates of the current mirror tube M2 and the current mirror tube M3, and control the current mirror tube M2 and the gate voltage of the current mirror tube M3 to form a feedback loop.

The second current generating circuit comprises a current mirror tube M1, a load tube M11, a resistor R2, an amplifier OP21, a feedback tube M9, and a load tube M5; the source of the current mirror tube M1 is connected to VDD, and the gate is connected to the gates of the current mirror tubes M2 and M3 The pole and drain are connected to the positive input terminal of the amplifier OP21 and the drain and gate of the load tube M11. The load tube M11 is in a diode connection mode. The source of the load tube M11 and one end of the resistor R2 are grounded, and the other end of the resistor R2 is connected to the feedback tube. The source of M9 and the negative input terminal of the amplifier OP21, the output terminal of the amplifier OP21 is connected to the gate of the feedback tube M9, the drain of the feedback tube M9 is connected to the gate and drain of the current mirror tube M5, and the source of the current mirror tube M5 is connected to VDD, In a diode connection mode, the amplifier OP21 forms a feedback loop with the feedback tube M9, the resistor R2 and the load tube M11.

The third current generating circuit includes a triode Q2, a resistor R3, an amplifier OP22, a feedback tube M10, and a load tube M7; the positive input terminal of the amplifier OP22 is connected to the emitter of the triode Q2, the negative input terminal is connected to the source of M10 and one end of the resistor R3, The other end of the resistor R3 is grounded, the output terminal of the amplifier OP22 is connected to the gate of the feedback tube M10, the drain of the feedback tube M10 is connected to the drain and gate of the current mirror tube M7, the source of the current mirror tube M7 is connected to VDD, and is diode-connected In this way, the amplifier OP22 forms a feedback loop with the feedback tube M10, the resistor R3 and the transistor Q2.

The current superposition circuit includes a resistor R4, a current mirror tube M4, a current mirror tube M6 and a current mirror tube M8; the sources of the current mirror tubes M4, M6 and M8 are connected to VDD, the drains are connected to one end of the resistor R4, and the gates are respectively connected to the current mirror The gates of tubes M3, M5 and M7, and the other end of resistor R4 are grounded.

In this embodiment, the current mirror tube M1, the current mirror tube M2, the current mirror tube M3 and the current mirror tube M4 have the same width-to-length ratio, and are connected by a current mirror; the load tube M5 and the current mirror tube M6 have the same width and length Ratio, and is a current mirror connection; the load tube M7 and the current mirror tube M8 have the same width-to-length ratio, and is a current mirror connection.

The working principle of the bandgap reference voltage source provided by the embodiment of the present invention is as follows:

The two input terminals of the amplifier OP1 in the first current generating circuit are respectively connected to the node A and the node B, and the output terminal of the amplifier OP1 controls the gate voltage of the current mirror composed of the current mirror tubes M1, M2, M3, and M4 to form a feedback loop, Amplifier OP1 works in deep negative feedback so that the voltages at A and B are equal, that is

V _A = V _B (4);

Since the current mirror tubes M1, M2, M3 and M4 have the same aspect ratio, and they are current mirror connections, so

${\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; BE</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; BE</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}}{{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="R"\; filenames="HDA0000151396460000011.png,HDA0000151396460000012.png"\; state="\{\{state\}\}">R</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; T</span>}}\mathrm{<span\; class="notranslate">\; ln</span>}\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; N</span>}}{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 5</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ,</span>$

V _BE1 and V _BE2 are the base-emitter voltages of transistors _Q1 and _Q2 , and N is the ratio of the areas of _Q1 and _Q2 .

I ₂ is proportional to V _T , that is, I ₂ is a current proportional to absolute temperature;

The feedback loop formed by the amplifier OP21 in the second current generation circuit, the feedback tube M9, the resistor R2 and the load tube M11 makes the voltage across the resistor R2 be V _GS , therefore, the current I ₅ flowing through the load tube M5 and the feedback tube M9 for

${\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; 5</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; GS</span>}}}{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 6</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ;</span>$

Assuming that the load tube M11 works in the strong inversion region, from the square rate relationship of the MOS device, we can get

${\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; GS</span>}}<span\; class="notranslate">\; =</span>\sqrt{\frac{\mathrm{<span\; class="notranslate">\; 2</span>}{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; ox</span>}}{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; W</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; L</span>}<span\; class="notranslate">\; )</span>}_{\mathrm{<span\; class="notranslate">\; 11</span>}}}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; T</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 7</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ;</span>$

Among them, Un is the medium carrier mobility of NMOS, Cox is the oxide layer capacitance between the gate and the channel, and W/L is the width-to-length ratio of the MOS transistor.

Due to the influence of ionized impurity scattering and acoustic wave scattering, the mobility Un has a complex relationship with temperature. In the strong inversion region, when the temperature is above 300K, the effective mobility in the inversion layer has a relationship with the temperature of T ^-2 Power exponential relationship, the threshold voltage V _T also has a complex relationship with temperature; their common influence makes the first-order temperature coefficient of V _GS in a certain temperature range negative, and the second-order temperature coefficient is positive; it may be assumed that

V _GS = β ₀ + β ₁ T + β ₂ T ² (8),

Wherein, β ₀ >0, β ₂ >0, and β ₁ <0.

Assuming that the temperature coefficient of resistor R2 is neglected, _I5 has a negative first-order temperature coefficient and a positive second-order temperature coefficient. The load tube M5 and the current mirror tube M6 constitute a current mirror and have the same width-to-length ratio, so

I ₆ =I ₅ (9);

The feedback loop formed by the amplifier OP22 in the third current generation circuit, the feedback tube M10, the resistor R3 and the transistor Q2 makes the voltage across the resistor R3 be V _BE2 , so the current I flowing through the feedback tube M10, the resistor R3 and the load tube M7 ₇ for

${\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; 7</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; BE</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}}{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 10</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ,</span>$

V _BE2 has both the first-order temperature coefficient and the second-order temperature coefficient are negative, it may be set

V _BE2 = α ₀ + α ₁ T + α ₂ T ² (11),

Wherein, α ₀ >0, α ₁ <0, and α ₂ <0. Assuming that the temperature coefficient of resistance is ignored, I ₇ has a negative first-order temperature coefficient and a negative second-order temperature coefficient. The load tube M7 and the current mirror tube M8 constitute a current mirror and have the same width-to-length ratio, so

I ₈ =I ₇ (12);

The current superposition circuit includes resistor R4, current mirror tubes M4, M6 and M8, and three amplifiers form three feedback loops to generate three currents I ₄ , I ₆ and I ₈ flow through resistor R4, and the obtained output voltage V _REF is

${\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; REF</span>}}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; 6</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; 8</span>}}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; T</span>}}\mathrm{<span\; class="notranslate">\; ln</span>}\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; N</span>}<span\; class="notranslate">\; )</span>\frac{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}}{{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="R"\; filenames="HDA0000151396460000011.png,HDA0000151396460000012.png"\; state="\{\{state\}\}">R</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; GS</span>}}\frac{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}}{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; BE</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}\frac{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}}{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 13</span>}<span\; class="notranslate">\; )</span>$

Substituting formulas (8) and (11) into (13), we get

${\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; REF</span>}}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}\frac{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}}{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&beta;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}\frac{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}}{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span><span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; k</span>}}{\mathrm{<span\; class="notranslate">\; q</span>}}\mathrm{<span\; class="notranslate">\; ln</span>}\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; N</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}\frac{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}}{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&beta;</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}\frac{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}}{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; T</span>}<span\; class="notranslate">\; +</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}\frac{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}}{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&beta;</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}\frac{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}}{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; T</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 14</span>}<span\; class="notranslate">\; )</span>$

Properly adjust the values of N, R4/R2 and R4/R3 in the formula (14), so that the first-order coefficient and the second-order coefficient of temperature are both zero, and the reference voltage with zero temperature coefficient of the second-order compensation can be generated.

Compared with the bandgap reference voltage source circuit shown in Figure 1, the bandgap reference voltage source circuit provided by the present invention adopts the method of superimposing three currents with different temperature characteristics, so that the first-order and second-order temperatures of the superimposed current The coefficient tends to zero, so the temperature coefficient of the output reference voltage is much smaller than the temperature coefficient of the output voltage of the circuit shown in Figure 1, effectively improving the accuracy of the bandgap reference voltage source; and, the bandgap reference circuit provided by the present invention The adopted structure enables the output reference voltage to be adjusted according to actual needs, and since the amplifier can normally work in a low-voltage circuit, the entire bandgap reference voltage circuit can work normally at a lower power supply voltage.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims (8)

1. A low-voltage high-precision bandgap reference voltage source is characterized in that: comprising a first current generating circuit, a second current generating circuit, a third current generating circuit and a current superposition circuit; The first current generating circuit is used to generate a current that is proportional to the temperature change; The second current generating circuit is used to generate a current with a negative first-order temperature coefficient and a positive second-order temperature coefficient; The third current generating circuit is used to generate a current with a negative first-order temperature coefficient and a negative second-order temperature coefficient; The current superimposition circuit is used to superimpose the three currents generated by the first current generation circuit, the second current generation circuit and the third current generation circuit, and the superimposed current provides the output value through the adjustment resistor. required reference voltage. 2. The low-voltage high-precision bandgap reference voltage source as claimed in claim 1, characterized in that: said first current generating circuit comprises triode Q1 and triode Q2, resistor R1, current mirror tubes M2 and M3, amplifier OP1; The emitter of Q1 is connected to the drain of the current mirror tube M2 through the resistor R1, the emitter of the triode Q2 is connected to the drain collector of the current mirror tube M3, and the sources of the current mirror tube M2 and the current mirror tube M3 are respectively connected to the power supply voltage V _DD , the collectors of transistor Q1 and transistor Q2 are grounded respectively; the two input terminals of amplifier OP1 are respectively connected to node A between resistor R1 and current mirror tube M2 and node B between transistor Q2 and current mirror tube M3, the amplifier OP1 The output terminal is connected to the gates of the current mirror tube M2 and the current mirror tube M3, and controls the gate voltage of the current mirror tube M2 and the current mirror tube M3 to form a feedback loop. 3. The low-voltage high-precision bandgap reference voltage source as claimed in claim 2, characterized in that: the second current generating circuit comprises a current mirror tube M1, a load tube M11, a resistor R2, an amplifier OP21, a feedback tube M9, and a current mirror tube M5; the source of the current mirror tube M1 is connected to VDD, the grid of the current mirror tube M1 is connected to the grids of the current mirror tube M2 and the current mirror tube M3, and the drain of the current mirror tube M1 is connected to the positive input terminal of the amplifier OP21 and The drain and gate of the load tube M11, the load tube M11 is in a diode connection mode, the source of the load tube M11 and one end of the resistor R2 are commonly grounded, and the other end of the resistor R2 is connected to the source of the feedback tube M9 and the negative input terminal of the amplifier OP21 , the output terminal of the amplifier OP21 is connected to the grid of the feedback tube M9, the drain of the feedback tube M9 is connected to the grid and drain of the current mirror tube M5, the source of the current mirror tube M5 is connected to VDD, and is in a diode connection mode, the amplifier OP21 and The feedback tube M9, the resistor R2 and the load tube M11 form a feedback loop. 4. The low-voltage high-precision bandgap reference voltage source as claimed in claim 3, characterized in that: the third current generating circuit comprises a triode Q2, a resistor R3, an amplifier OP22, a feedback tube M10, a current mirror tube M7; an amplifier OP22 The positive input terminal of the amplifier OP22 is connected to the emitter of the transistor Q2, the negative input terminal of the amplifier OP22 is connected to the source of the feedback tube M10 and one end of the resistor R3, the other end of the resistor R3 is grounded, the output terminal of the amplifier OP22 is connected to the gate of the feedback tube M10, The drain of the feedback tube M10 is connected to the drain and gate of the current mirror tube M7, and the source of the current mirror tube M7 is connected to VDD in a diode connection mode. The amplifier OP22 forms a feedback loop with the feedback tube M10, the resistor R3 and the transistor Q2. 5. low-voltage high-precision bandgap reference voltage source as claimed in claim 4, is characterized in that: described current superposition circuit comprises resistance R4, current mirror tube M4, current mirror tube M6 and current mirror tube M8; Current mirror tube M4 The sources of the current mirror tube M6 and the current mirror tube M8 are connected to VDD, the drains are connected to one end of the resistor R4, the gates are respectively connected to the grids of the current mirror tube M3, the current mirror tube M5 and the current mirror tube M7, and the other end of the resistor R4 grounded. 6. The low-voltage high-precision bandgap reference voltage source as claimed in claim 5, characterized in that: the current mirror tube M1, the current mirror tube M2, the current mirror tube M3 and the current mirror tube M4 have the same width-to-length ratio, And it is a current mirror connection. 7. The low-voltage high-precision bandgap reference voltage source according to claim 5, wherein the load tube M5 and the current mirror tube M6 have the same width-to-length ratio, and are connected by a current mirror. 8. The low-voltage high-precision bandgap reference voltage source according to claim 5, wherein the load tube M7 and the current mirror tube M8 have the same width-to-length ratio, and are connected by a current mirror.

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