CN101093401A - Bandgap Voltage Reference Circuit - Google Patents

Abstract

The invention provides a band gap voltage reference circuit, which comprises an operational amplifier, a first voltage reference circuit, a second voltage reference circuit, a first voltage reference circuit and a second voltage reference circuit, wherein the operational amplifier is provided with an output end, a first input end and a second input end; the first transistor and the second transistor are coupled to the operational amplifier; a first resistor coupled between the output of the operational amplifier and the first transistor; and a first resistor ladder coupled between the output terminal of the operational amplifier and the second transistor, wherein the first resistor ladder comprises a plurality of second resistors connected in series, and each of the plurality of switching elements has a first terminal coupled to a high impedance path.

Description

Bandgap Voltage Reference Circuit

technical field

The present invention relates to a reference circuit, in particular to a bandgap voltage reference circuit capable of providing a reference voltage not affected by finite turn-on resistance and temperature coefficient of switching elements.

Background technique

Generally speaking, voltage reference circuits and current reference circuits are widely used in analog circuits. This type of reference circuit is mainly based on DC voltage or current, which is not greatly affected by power supply and process parameters, and will be consistent with temperature changes. predetermined dependencies. For example, the bandgap voltage reference circuit is the most commonly used high-efficiency voltage reference circuit, which uses elements with positive temperature coefficient and negative temperature coefficient characteristics, and then sums the voltage or current generated by these elements according to a predetermined ratio , in order to generate a temperature-independent output as a reference current or current.

Contents of the invention

The present invention provides a bandgap voltage reference circuit, comprising an operational amplifier having an output terminal and first and second input terminals; first and second diode-connected transistors coupled to the operational amplifier; a first a resistor coupled between the output terminal of the operational amplifier and the first diode-connected transistor; and a first resistor ladder (resistor ladder) coupled between the output terminal of the operational amplifier and the second diode-connected transistor between, and the first resistor ladder includes a plurality of second resistors connected in series; and a plurality of switching elements, each having a first end coupled to the first input end of the operational amplifier.

The present invention also provides a bandgap voltage reference circuit, comprising an operational amplifier having an output terminal and first and second input terminals; the first and second diode-connected transistors are respectively coupled to the first operational amplifier. 1. The second input terminal; a first resistor has a first terminal coupled to the output terminal of the operational amplifier, and a second terminal coupled to the first diode-connected transistor and the first input terminal of the operational amplifier; and a first resistor ladder (resistor ladder), coupled between the output terminal of the operational amplifier and the second diode-connected transistor, and the first resistor ladder includes a plurality of second resistors connected in series; and a plurality of switches elements, each having a first end coupled to a high impedance path, wherein the switch element is controlled by a first set of control signals, so that part of the second resistance will form a first equivalent resistance, and the remaining second The resistance forms a second equivalent resistance.

The present invention also provides a bandgap voltage reference circuit, comprising an operational amplifier having an output terminal and first and second input terminals; the first and second transistors are coupled to the operational amplifier; a first resistor is coupled to the operational amplifier between the output terminal of the amplifier and the first transistor; and a first resistor ladder coupled between the output terminal of the operational amplifier and the second transistor, and the first resistor ladder includes a plurality of second resistors connected in series, and a plurality of switches Each element has a first end coupled to a high impedance path.

The bandgap voltage reference circuit provided by the present invention can provide a reference voltage not affected by the finite turn-on resistance (finite turn-on resistance) and temperature coefficient of the switch element.

Description of drawings

FIG. 1 is an embodiment of a bandgap voltage reference circuit in the present invention.

Fig. 2 is an embodiment of the resistance ladder in the present invention.

FIG. 3 is another embodiment of the bandgap voltage reference circuit in the present invention.

FIG. 4 is another embodiment of the bandgap voltage reference circuit in the present invention.

Figure number:

10A, 20, 30: bandgap voltage reference circuit;

22, 24: resistance ladder;

OP: operational amplifier;

Q1, Q2: bipolar transistors;

V1～V2: Voltage;

GND: ground voltage;

I1, I2: current;

Vbg, Vbg": output voltage;

ND20～ND2M, ND30～ND3Z: nodes;

R1～R3, R3 1～R3N, RX1～RXN, R41～R4Y: resistance;

SW10～SW1A, SW20～SW2M, SW30～SW3Z: switching elements.

Detailed ways

In order to make the above-mentioned and other objects, features, and advantages of the present invention more obvious and understandable, a preferred embodiment is specifically cited below, together with the accompanying drawings, and is described in detail as follows:

FIG. 1 shows an embodiment of a bandgap voltage reference circuit in the present invention. As shown in the figure, the bandgap voltage reference circuit 10A includes an operational amplifier OP, bipolar transistors (BJTs) Q1 and Q2 , and resistors R1 - R3 . For example, the resistors R1 and R2 have the same resistance value, and the area of the emitter of the transistor Q2 is N times the area of the emitter of the transistor Q1, where N is greater than 1.

If the base current is neglected, the emitter-base voltage VEB of a forward-conducting diode can be expressed as:

${\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; EB</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; kT</span>}}{\mathrm{<span\; class="notranslate">\; q</span>}}\mathrm{<span\; class="notranslate">\; ln</span>}<span\; class="notranslate">\; (</span>\frac{{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; C</span>}}}{{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; S</span>}}}<span\; class="notranslate">\; )</span>$

Where k is Boltzmann's constant (1.38×10 ^-23 J/K), q is charge quantity (1.6×10 ^-29 C), T is temperature, I _C is collector current, and I _S is saturation current.

When the input voltages V1 and V2 of the operational amplifier OP match each other and the size of the transistor Q2 is N times that of the transistor Q1, the emitter-base voltage difference ΔV _EB between the transistors Q1 and Q2 can be expressed as:

$\mathrm{<span\; class="notranslate">\; \&Delta;</span>}{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; EB</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; EB</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; EB</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; kT</span>}}{\mathrm{<span\; class="notranslate">\; q</span>}}\mathrm{<span\; class="notranslate">\; ln</span>}\mathrm{<span\; class="notranslate">\; N</span>}$

Where V _EB1 is the emitter-base voltage of transistor Q1, and V _EB2 is the emitter-base voltage of transistor Q2.

Since the input voltages V1 and V2 match each other due to the operational amplifier OP (virtual short circuit), the input voltages V1 and V2 can be expressed as:

V1=V2=V _EB1 =V _EB2 +I2×R3

$\mathrm{<span\; class="notranslate">\; I</span>}\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; I</span>}\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; EB</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; EB</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; kT</span>}}{\mathrm{<span\; class="notranslate">\; q</span>}}\mathrm{<span\; class="notranslate">\; ln</span>}\mathrm{<span\; class="notranslate">\; N</span>}$

Therefore, the current I2 through the resistors R2 and R3 can be expressed as:

$I2=\frac{V_T}{R3}\ln N,$ Where temperature voltage (thermal voltage) $V_T=\frac{\mathrm{kT}}{q}.$

Since the resistors R1 and R2 have the same resistance and the input voltages V1 and V2 are matched by the operational amplifier OP (virtual short circuit), the current I2 will be equal to the current I1.

then, $\mathrm{<figure-callout\; id="1"\; label="I"\; filenames="A20071011253500121.png,A20071011253500151.png"\; state="\{\{state\}\}">I</figure-callout>}1=I2=\frac{V_T}{R3}\ln N,$ And because the temperature voltage V _T has a positive temperature coefficient of 0.085mV/°C, the currents I1 and I2 also have a positive temperature coefficient.

Therefore, the voltage Vbg can also be expressed as:

$\mathrm{<span\; class="notranslate">\; Vbg</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; I</span>}\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; \&times;</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; R</span>}\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; R</span>}\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; EB</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; I</span>}\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="R"\; filenames="A20071011253500121.png,A20071011253500151.png"\; state="\{\{state\}\}">R</figure-callout></span>}\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; EB</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}$

$<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; R</span>}\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; \&times;</span>\frac{{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; T</span>}}}{\mathrm{<span\; class="notranslate">\; R</span>}\mathrm{<span\; class="notranslate">\; 3</span>}}\mathrm{<span\; class="notranslate">\; ln</span>}\mathrm{<span\; class="notranslate">\; N</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; EB</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}$

Since the emitter-base voltage V _EB of the transistor has a negative temperature coefficient of -2mV/°C, if the ratio of the resistance values of the resistors R1 to R3 is properly selected, the current Vbg will have a nearly zero temperature coefficient and is less affected by Effects of temperature changes.

In some embodiments, the resistor R3 is realized by a resistor ladder. Fig. 2 is an embodiment of a resistance ladder. The resistor R3 is coupled between the resistor R2 and the transistor Q2, and includes N resistors R31-R3N connected in series, and N switch elements SW1-SW1A connected in series. Except for the resistors R31 and R3N, each switch element SW1˜SW1A is connected in parallel with a corresponding resistor. For example, the two ends of the switch element SW10 are coupled to the two ends of the resistor R32, the two ends of the switch element SW11 are coupled to the two ends of the resistor R33, and so on. Switching elements SW10-SW1N can be realized by MOS transistors.

Since the switching elements SW10 - SW1A are disposed in the path of the current I2 , non-ideal switching effects (such as temperature coefficient, finite on-resistance) will affect the parameters of the bandgap reference circuit. For example, when the switch element SW10 is turned on, the current I2 will flow through the resistor R31, the switch element SW10 and the resistors R33-R3N, so the non-ideal effect on the switch element SW10 will affect the parameters of the bandgap reference circuit. Furthermore, assuming that the switching elements SW10˜SW1N are implemented by PMOS transistors, the N-well region coupled to the power supply voltage will also degrade the performance of the power supply rejection ratio of the bandgap reference circuit. After obtaining the optimum setting value of the switching element array (SW10-SW1M), these switching elements will be implemented by hardware circuits when considering the power supply rejection ratio. Due to the difference in characteristics between switching elements and hardware circuits, the parameters of the energy bandgap reference circuit will drift.

The best way to avoid the finite turning on resistance and temperature coefficient of the switching elements is to place them on a high impedance path, and in an operational amplifier type bandgap voltage reference circuit, the high impedance path is present at the input of the operational amplifier. Therefore, the present invention also provides a bandgap voltage reference circuit that is not affected by the finite on-resistance and temperature coefficient of the switching element.

FIG. 3 is another embodiment of a bandgap voltage reference circuit. As shown, the bandgap voltage reference circuit 20 is similar to the bandgap voltage reference circuit 10A shown in FIG. 1 except for the resistor ladder 22 . The bandgap voltage reference circuit 20 includes bipolar transistors Q1 and Q2 , an operational amplifier OP, a resistor R1 and a resistor ladder 22 .

The transistor Q1 includes an emitter coupled to the positive input terminal of the operational amplifier OP, a base and a collector coupled to the ground voltage GND. The transistor Q2 includes an emitter coupled to the resistor ladder 22 and a base and a collector coupled to the ground voltage GND. In other words, the transistors Q1 and Q2 are diode-connected transistors. The resistor R1 is coupled between the positive input terminal and the output terminal of the operational amplifier OP, and the resistor ladder 22 is coupled between the emitter of the transistor Q2 and the negative input terminal and the output terminal of the operational amplifier OP.

The resistance ladder 22 includes a plurality of resistors RX1 to RXN and a plurality of switching elements SW21 to SW22 connected in series. The resistor RX1 is coupled between the output terminal of the operational amplifier OP and the node ND20, the resistor RX2 is coupled between the node ND20 and the node ND21, and so on, and the resistor RXN is coupled between the node ND2M and the emitter of the transistor Q2 . Each switch element SW20˜SW2M has a first terminal coupled to a corresponding node, and a second terminal coupled to the negative input terminal of the operational amplifier OP. For example, the switch element SW20 is coupled between the negative input terminal of the operational amplifier OP and the node ND20 , the switch element SW21 is coupled between the negative input terminal of the operational amplifier OP and the node ND21 , and so on. The switch element SW2M is coupled between the negative input terminal of the operational amplifier OP and the node ND21.

The resistor string (ie, the resistor ladder 22 ) including the resistors RX1 - RXN has a fixed total resistance, and the resistors R2 and R3 shown in FIG. 1 can be adjusted by the switch elements SW21 - SW2M. For example, when the switch element SW20 is turned on and the switch elements SW21˜SW2M are turned off, the resistor RX1 acts as a first equivalent resistor (resistor R2 shown in FIG. 1 ), and the remaining resistors RX2˜RXN in the resistor string is used as a second equivalent resistor (resistor R3 shown in FIG. 1). In another example, when the switch element SW21 is turned on and the switch elements SW20 and SW22-SW2M are turned off, the resistor string including resistors RX1-RX2 is used as the first equivalent resistor (R2 shown in FIG. 1 ), and includes The resistor string of resistors RX3 - RXN is used as the second equivalent resistor (R3 as shown in FIG. 1 ). When the switch element SW22 is turned on and the switch elements SW20~SW21 and SW23~SW2M are turned off, the resistor string including resistors RX1~RX3 is used as the first equivalent resistor (R2 shown in Figure 1), and includes resistors RX4~RXN The resistor string is used as the second equivalent resistor (R3 shown in Figure 1), and so on. By turning on one of the switch elements, the ratio of the first and second equivalent resistors (R2 and R3 shown in FIG. 1 ) can be adjusted. Since the input terminal of the operational amplifier OP is high impedance, no current flows into the operational amplifier OP through the switching elements SW21 - SW2M, and the current I2 only flows through the resistors RX1 - RXN and the transistor Q2.

Therefore, if the ratio of the resistance values of the resistors R1-R3 can be properly selected, the output voltage Vbg' of the bandgap voltage reference circuit 20 will also have a temperature coefficient close to zero and be less sensitive to temperature. In some embodiments, the transistors SW20-SW2M are controlled by a set of control signals from an external control device, so that the resistors R2-R3 can be adjusted to obtain the desired output voltage Vbg'.

FIG. 4 is another embodiment of a bandgap voltage reference circuit. As shown, the bandgap voltage reference circuit 30 is similar to the bandgap voltage reference circuit 20 shown in FIG. 3 except for the resistor ladder 24 . The resistor ladder 24 is coupled between the output terminal of the operational amplifier OP and the ground voltage GND, and includes a plurality of resistors R41 - R4Y and a plurality of switch elements SW30 - SW3Z connected in series. The resistor R41 is coupled between the output terminal of the operational amplifier OP and the node ND30 , the resistor R42 is coupled between the node ND30 and the node ND31 , and so on, and the resistor R4Y is coupled between the node ND3Z and the ground voltage GND. Each of the switch elements SW30˜SW3Z has a first end coupled to a corresponding node, and a second end connected to an output end.

For example, the switch SW30 is coupled between the output terminal and the node ND30 , the switch SW31 is coupled between the output terminal and the node ND31 , and so on, the switch SW3Z is coupled between the output terminal and the node ND3Z. The resistance ladder 24 divides the output voltage Vbg′ by turning on one of the switching elements SW30˜SW3Z, so that the output voltage Vbg″ can be lower than the output voltage Vbg′, so as to operate in a low voltage environment. In some embodiments, the switching elements SW30 and SW3Z can be controlled by another resistance control signal from an external control device, so that the output voltage Vbg″ can be operated in a low voltage environment.

When the switching elements SW20-SW2M each have one end coupled to an input end of the operational amplifier OP (ie, a high-impedance path), so no current flows through the switching elements SW20-SW2M to the operational amplifier OP, so the switching elements SW20-SW2M (transistor) does not affect the parameters of the bandgap voltage reference circuit. Since no current flows through the switching element (transistor), even when considering the power rejection ratio, the influence of the characteristics of the switching element and the hardware circuit is different, and the switching element is controlled by the hardware circuit after obtaining the optimum setting value. Instead, the parameters of the bandgap voltage reference circuit will remain unaffected.

The bandgap voltage reference circuits 10A, 20, and 30 are necessary functional blocks that can act as mixed-mode integrated circuits or analog integrated circuits, such as data converters, phase-locked loops (PLLs), oscillators, Power management circuit, dynamic random access memory (DRAM), flash memory (FLASH)...etc. For example, the bandgap voltage reference circuit 30 provides the output voltage Vbg″ to a core circuit so that the core circuit can perform its functions.

Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Any skilled person may make some changes and modifications without departing from the spirit and scope of the present invention. Therefore, the present invention The scope of protection should be determined by what is defined in the claims.

Claims (19)

1. a band gap reference circuits is characterized in that, this band gap reference circuits comprises:

One operational amplifier comprises an output terminal and first, second input end;

The transistor that one first, 1 second diode form connects;

Between one first resistance, the output terminal that is coupled to above-mentioned operational amplifier and the transistor that the above-mentioned first diode form is connected; And

Between one first resistor ladder, the output terminal that is coupled to above-mentioned operational amplifier and the transistor that the above-mentioned second diode form is connected, above-mentioned first resistor ladder comprises:

Plural number second resistance is connected in series; And

The plural number on-off element respectively has the first input end that one first end is coupled to above-mentioned operational amplifier.

2. band gap reference circuits as claimed in claim 1, it is characterized in that above-mentioned first resistance comprises that output terminal and one second end that one first end is coupled to above-mentioned operational amplifier are coupled to second input end of above-mentioned operational amplifier and the transistor of the above-mentioned first diode type of attachment.

3. band gap reference circuits as claimed in claim 1, it is characterized in that, the transistor of the above-mentioned first diode type of attachment is to be coupled between second input end and a ground voltage of above-mentioned operational amplifier, and the transistor of the above-mentioned second diode type of attachment is to be coupled between above-mentioned first resistor ladder and the above-mentioned ground voltage.

4. band gap reference circuits as claimed in claim 1, it is characterized in that, in above-mentioned first resistor ladder, can have a node between per two above-mentioned second resistance, and above-mentioned each on-off element is to be coupled between the corresponding node with of first input end of above-mentioned operational amplifier.

5. band gap reference circuits as claimed in claim 1 is characterized in that, above-mentioned on-off element is a transistor.

6. band gap reference circuits as claimed in claim 1 is characterized in that, this band gap reference circuits comprises that also a sectional pressure element is coupled to the output terminal of above-mentioned operational amplifier.

7. band gap reference circuits as claimed in claim 6 is characterized in that, above-mentioned sectional pressure element is one second resistor ladder.

8. a band gap reference circuits is characterized in that, this band gap reference circuits comprises:

One operational amplifier comprises an output terminal and first, second input end;

First, second transistor;

One first resistance is coupled between the output terminal and above-mentioned the first transistor of above-mentioned operational amplifier; And

One first resistor ladder is coupled between the output terminal and above-mentioned transistor seconds of above-mentioned operational amplifier, and above-mentioned first resistor ladder comprises that plural second resistance is connected in series, and plural on-off element respectively has one first end and is coupled to a high resistive path.

9. band gap reference circuits as claimed in claim 8 is characterized in that, above-mentioned first, second transistor is the transistor of diode type of attachment.

10. band gap reference circuits as claimed in claim 9, it is characterized in that, above-mentioned first resistance is coupled to the output terminal of above-mentioned operational amplifier and reaches between the ground voltage, and above-mentioned transistor seconds is to be connected between above-mentioned first resistor ladder and the above-mentioned ground voltage.

11. band gap reference circuits as claimed in claim 10, it is characterized in that, above-mentioned first resistor ladder comprises that one first end couples the output terminal of above-mentioned operational amplifier, and one second end couples the first input end and the above-mentioned the first transistor of above-mentioned operational amplifier.

12. band gap reference circuits as claimed in claim 11, it is characterized in that, in above-mentioned first resistor ladder, can have a node between per two continuous above-mentioned second resistance, and above-mentioned each on-off element is to be coupled between the corresponding node with of above-mentioned high resistive path.

13. band gap reference circuits as claimed in claim 12 comprises that also one second resistor ladder is coupled to the output terminal of above-mentioned operational amplifier.

14. band gap reference circuits as claimed in claim 13 is characterized in that, above-mentioned high resistive path is second input end of above-mentioned operational amplifier.

15. a band gap reference circuits is characterized in that, this band gap reference circuits comprises:

One operational amplifier comprises an output terminal and first, second input end;

The transistor that first, second diode form connects is coupled to first, second input end of above-mentioned operational amplifier respectively;

One first resistance comprises that one first end is coupled to the output terminal of above-mentioned operational amplifier, and one second end couples the first input end of the above-mentioned operational amplifier of transistor AND gate of above-mentioned first diode form connection; And

Between one first resistor ladder, the output terminal that is coupled to above-mentioned operational amplifier and the transistor that the above-mentioned second diode form is connected, above-mentioned first resistor ladder comprises:

Plural number second resistance is connected in series; And

The plural number on-off element, respectively have one first end and be coupled to a high resistive path, wherein above-mentioned on-off element is controlled by one first group of control signal, make above-mentioned second resistance of part can form one first equivalent resistance, and remaining above-mentioned second resistance can form one second equivalent resistance.

16. band gap reference circuits as claimed in claim 15, it is characterized in that, in above-mentioned first resistor ladder, per two continuous above-mentioned second resistance can have a node, and above-mentioned each on-off element is to be coupled between the corresponding node with of above-mentioned high resistive path.

17. band gap reference circuits as claimed in claim 15 is characterized in that, above-mentioned high resistive path is second input end of above-mentioned operational amplifier.

18. band gap reference circuits as claimed in claim 15 is characterized in that, above-mentioned first, second equivalent resistance has a fixing total resistance value, and the resistance value of above-mentioned first, second equivalent resistance ratio is adjusted by above-mentioned first group of control signal.

19. band gap reference circuits as claimed in claim 15 is characterized in that, this band gap reference circuits comprises that also one second resistor ladder is coupled to the output terminal of above-mentioned operational amplifier, in order to according to one second group of control signal, carries out the voltage dividing potential drop.

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