CN101093401A - Bandgap reference circuits - Google Patents

Abstract

Bandgap reference circuits capable operating in low voltage environments. In the bandgap reference circuit, an operational amplifier comprises an output terminal and first and second input terminals, first and second transistors are coupled to the operational amplifier, and a first resistor is coupled between the output terminal of operational amplifier and the first transistor. A first resistor ladder is coupled between the output terminal of the operational amplifier and the second transistor and comprises a plurality of second resistors connected in series and a plurality of switches each having a first terminal coupled to a high-impendence path.

Description

The band gap reference circuits

Technical field

The present invention is relevant for reference circuit, and relevant especially a kind of band gap reference circuits can provide the limited conducting resistance (finite turn-on resistance) that the is not subjected to on-off element reference voltage with the temperature coefficient influence.

Background technology

Generally speaking, reference circuits and current reference circuit are used in the mimic channel widely, and this type of reference circuit is based on DC voltage or electric current, are subjected to the influence of power supply and process parameter little, and temperature variation had meet a predetermined dependence.For example, the band gap reference circuits is the most frequently used high-level efficiency reference circuits, its use has the element of positive temperature coefficient (PTC) and negative temperature coefficient feature, again voltage that these elements are produced or electric current according to one both certainty ratio added up so that produce temperature independent output as a reference current or electric current.

Summary of the invention

The invention provides a kind of band gap reference circuits, comprise that an operational amplifier has an output terminal and first, second input end; The transistor that first, second diode form connects is coupled to operational amplifier; Between the output terminal that one first resistance is coupled to operational amplifier and the transistor that the first diode form is connected; And one first between resistor ladder (resistor ladder) output terminal that is coupled to operational amplifier and the transistor that the second diode form is connected, and first resistor ladder comprises plural number second resistance that is connected in series; And plural on-off element, respectively have the first input end that one first end is coupled to operational amplifier.

The present invention also provides a kind of band gap reference circuits, comprises that an operational amplifier has an output terminal and first, second input end; The transistor that first, second diode form connects is coupled to first, second input end of operational amplifier respectively; One first resistance has the output terminal that one first end is coupled to operational amplifier, and one second end couples the first input end of the transistor AND gate operational amplifier of first diode form connection; And one first resistor ladder (resistor ladder), between the output terminal that is coupled to operational amplifier and the transistor that the second diode form is connected, and first resistor ladder comprises plural number second resistance that is connected in series; And plural on-off element, respectively have one first end and be coupled to a high resistive path, wherein on-off element is controlled by one first group of control signal, make second resistance of part can form one first equivalent resistance, and remaining second resistance can form one second equivalent resistance.

The present invention also provides a kind of band gap reference circuits, comprises that an operational amplifier has an output terminal and first, second input end; First, second transistor is coupled to operational amplifier; One first resistance is coupled between the output terminal and the first transistor of operational amplifier; And one first resistor ladder be coupled between the output terminal and transistor seconds of operational amplifier, and first resistor ladder comprises plural number second resistance that is connected in series, and plural on-off element respectively has one first end and is coupled to a high resistive path.

Band gap reference circuits provided by the invention can provide the limited conducting resistance (finite turn-on resistance) that the is not subjected to on-off element reference voltage with the temperature coefficient influence.

Description of drawings

Fig. 1 is an embodiment of band gap reference circuits among the present invention.

Fig. 2 is an embodiment of resistor ladder among the present invention.

Fig. 3 is another embodiment of band gap reference circuits among the present invention.

Fig. 4 is another embodiment of band gap reference circuits among the present invention.

Drawing reference numeral:

10A, 20,30: band gap reference circuits;

22,24: resistor ladder;

OP: operational amplifier;

Q1, Q2: two-carrier transistor;

V1～V2: voltage;

GND: ground voltage;

I1, I2: electric current;

Vbg, Vbg ": output voltage;

ND20～ND2M, ND30～ND3Z: node;

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

SW10～SW1A, SW20～SW2M, SW30～SW3Z: on-off element.

Embodiment

For above-mentioned and other purposes of the present invention, feature and advantage can be become apparent, a preferred embodiment cited below particularly, and conjunction with figs. are described in detail below:

Fig. 1 is for showing an embodiment of band gap reference circuits among the present invention.As shown in the figure, band gap reference circuits 10A comprises operational amplifier OP, two-carrier transistor (BJTs) Q1 and Q2, and resistance R 1～R3.For example, resistance R 1 has identical resistance value with R2, and the area of the emitter-base bandgap grading of transistor Q2 is the N times of area to the emitter-base bandgap grading of transistor Q1, and N is greater than 1.

If ignore base current, forward the penetrating of the diode of conducting-base voltage VEB can be expressed as:

$V_{\mathrm{EB}}=\frac{\mathrm{kT}}{q}\ln \left(\frac{I_C}{I_S}\right)$

Wherein k is a Boltzmann's constant (1.38 * 10 ^-23J/K), q is a quantities of charge (1.6 * 10 ^-29C), T is a temperature, I _CBe collected current, and I _SBe saturation current.

When the input voltage V1 of operational amplifier OP and V2 mates mutually and transistor Q2 is of a size of transistor Q1 N doubly, transistor Q1 and Q2 penetrate-base voltage difference Δ V _EBCan be expressed as:

$\mathrm{\Δ}{V}_{\mathrm{EB}}=V_{\mathrm{EB}1}-V_{\mathrm{EB}2}=\frac{\mathrm{kT}}{q}\ln N$

V wherein _EB1Be penetrating-base voltage of transistor Q1, and V _EB2Be penetrating-base voltage of transistor Q2.

Because input voltage V1 and V2 mate (imaginary short) mutually because of operational amplifier OP, so input voltage V1 and V2 can be expressed as:

V1＝V2＝V _EB1＝V _EB2+I2×R3

$I2\×I3=V_{\mathrm{EB}1}-V_{\mathrm{EB}2}=\frac{\mathrm{kT}}{q}\ln N$

Therefore, can be expressed as by the electric current I 2 of resistance R 2 with R3:

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

Mate (imaginary short) mutually because of operational amplifier OP because resistance R 1 has identical resistance and input voltage V1 and V2 with R2, so electric current I 2 can equate with electric current I 1.

So, $\mathrm{<figure-callout\; id="1"\; label="I"\; filenames="A20071011253500121.png,A20071011253500151.png"\; state="\{\{state\}\}">I</figure-callout>}1=I2=\frac{V_T}{R3}\ln N,$ And because temperature voltage V _THas 0.085mV/ ℃ positive temperature coefficient (PTC), so electric current I 1 also has positive temperature coefficient (PTC) with I2.

Therefore, voltage Vbg also can be expressed as:

$\mathrm{Vbg}=I2\&times;(R2+R3)+V_{\mathrm{EB}2}=I1\&times;\mathrm{<figure-callout\; id="1"\; label="R"\; filenames="A20071011253500121.png,A20071011253500151.png"\; state="\{\{state\}\}">R</figure-callout>}1+V_{\mathrm{EB}1}$

$=R1\&times;\frac{V_T}{R3}\ln N+V_{\mathrm{EB}1}$

Because transistorized penetrating-base voltage V _EBHave-negative temperature coefficient of 2mV/ ℃, therefore if suitably select the ratio of the resistance value of resistance R 1～R3, electric current Vbg can have near-zero temperature coefficient and with more be not acted upon by temperature changes.

In some embodiment, resistance R 3 is to be realized by a resistor ladder.Fig. 2 is the embodiment of a resistor ladder.Resistance R 3 is to be coupled between resistance R 2 and the transistor Q2, and comprises N the resistance R 31～R3N that is connected in series, and the N that is connected in series on-off element SWl～SWlA.Except resistance R 31 and R3N, each on-off element SWl～SWlA is the resistance that is parallel to a correspondence.For example, the two ends of on-off element SW10 are the two ends that are coupled to resistance R 32, and the two ends of on-off element SW11 are the two ends that are coupled to resistance R 33, and the rest may be inferred.On-off element SW10～SW1N can realize by MOS transistor.

Because on-off element SW10～SW1A is arranged in the path of electric current I 2, make nonideal switching effect (for example temperature coefficient, finite conducting resistance) can influence the parameter of band gap reference circuit.For example, when on-off element SW10 conducting, electric current I 2 can flow through resistance R 31, on-off element SW10 and resistance R 33～R3N are so the non-ideal effects on the on-off element SW10 can influence the parameter of band gap reference circuit.Moreover, suppose that on-off element SW10～SW1N is realized by the PMOS transistor, the power rejection of band gap reference circuit also can be degenerated than the usefulness of (power supply rejectionratio) in the N wellblock that couples supply voltage.Obtain the on-off element array (behind the optimum setting value of SW10～SW1M), when consider power rejection than the time, these on-off elements will be realized by hardware circuit.Because different on characteristic of on-off element and hardware circuit, the parameter of band gap reference circuit will produce drift.

Avoiding the limited conducting resistance (finite turning on resistance) of on-off element and the best method of temperature coefficient is that they are arranged on the high resistive path, and in the band gap reference circuits of an operational amplifier formula, high resistive path is to be present on the input end of operational amplifier.Therefore, the present invention also provides a kind of limited conducting resistance of on-off element and band gap reference circuits that temperature coefficient influences of not being subjected to.

Fig. 3 is another embodiment of band gap reference circuits.As shown in the figure, band gap reference circuits 20 is similar to the band gap reference circuits 10A shown in Fig. 1 except resistor ladder 22.Band gap reference circuits 20 comprises two-carrier transistor Q1 and Q2, operational amplifier OP, resistance R 1 and resistor ladder 22.

Transistor Q1 comprises a base stage and the collection utmost point that an emitter-base bandgap grading is coupled to the positive input terminal of operational amplifier OP and is coupled to ground voltage GND.Transistor Q2 comprises a base stage and the collection utmost point that an emitter-base bandgap grading is coupled to resistor ladder 22 and is coupled to ground voltage GND.In other words, the transistor that is connected for the diode mode of transistor Q1 and Q2.Resistance R 1 is coupled between the positive input terminal and its output terminal of operational amplifier OP, and resistor ladder 22 couples between the negative input end and output terminal of the emitter-base bandgap grading of transistor Q2 and operational amplifier OP.

Resistor ladder 22 comprises plural resistance R X1～RXN and the plural on-off element SW21～SW22 that is connected in series.Resistance R X1 is coupled between the output terminal and node ND20 of operational amplifier OP, and resistance R X2 is coupled between node ND20 and the node ND21, and the rest may be inferred, and resistance R XN is coupled between the emitter-base bandgap grading of node ND2M and transistor Q2.Each on-off element SW20～SW2M all has the node that one first end is coupled to a correspondence, and one second end couples the negative input end of operational amplifier OP.For example, on-off element SW20 is coupled between the negative input end and node ND20 of operational amplifier OP, and on-off element SW21 is coupled between the negative input end and node ND21 of operational amplifier OP, and the rest may be inferred.On-off element SW2M is coupled between the negative input end and node ND21 of operational amplifier OP.

The resistance string (being resistor ladder 22) that comprises resistance R X1～RXN can have a fixing total resistance value, and shows in Fig. 1 institute that resistance R 2 and R3 can be adjusted by on-off element SW21～SW2M.For example, when on-off element SW20 conducting and on-off element SW21～SW2M by the time, resistance R X1 is as one first equivalent resistance (resistance R 2 as shown in Figure 1), and remaining resistance R X2～RXN is as one second equivalent resistance (resistance R 3 as shown in Figure 1) in the resistance string.In another example, when on-off element SW21 conducting and on-off element SW20 and SW22～SW2M by the time, the resistance string that comprises resistance R X1～RX2 is as first equivalent resistance (R2 as shown in Figure 1), and the resistance string that comprises resistance R X3～RXN is as second equivalent resistance (R3 as shown in Figure 1).When on-off element SW22 conducting and on-off element SW20～SW21 and SW23～SW2M by the time, the resistance string that comprises resistance R X1～RX3 is as first equivalent resistance (R2 as shown in Figure 1), and the resistance string that comprises resistance R X4～RXN is as second equivalent resistance (R3 as shown in Figure 1), and the rest may be inferred.By one in the turn-on switch component, can adjust the ratio of first, second equivalent resistance (R2 as shown in fig. 1 and R3).Because the input end of operational amplifier OP is a high impedance, does not therefore have electric current and flow into operational amplifier OP, 2 of electric current I can flow through resistance R X1～RXN and transistor Q2 by on-off element SW21～SW2M.

Therefore, if can suitably select the resistance value ratio of resistance R 1～R3, the output voltage V bg ' of band gap reference circuits 20 also can have and is similar to zero temperature coefficient and more insensitive to temperature.In some embodiment, transistor SW20～SW2M is controlled by one group of control signal from an external control device, makes resistance R 2～R3 to be adjusted, and the output voltage V bg ' that obtains wanting.

Fig. 4 is another embodiment of band gap reference circuits.As shown in the figure, band gap reference circuits 30 is similar to the band gap reference circuits 20 shown in Fig. 3 except resistor ladder 24.Resistor ladder 24 is coupled between the output terminal and ground voltage GND of operational amplifier OP, and comprises plural resistance R 41～R4Y and the plural on-off element SW30～SW3Z that is connected in series.Resistance R 41 is coupled between the output terminal and node ND30 of operational amplifier OP, and resistance R 42 is coupled between node ND30 and the node ND31, and the rest may be inferred, and resistance R 4Y is coupled between node ND3Z and the ground voltage GND.On-off element SW30～SW3Z respectively has the node that one first end is coupled to a correspondence, and one second is connected to an output terminal.

For example, switch SW 30 is coupled between output terminal and the node ND30, and switch SW 31 is coupled between output terminal and the node ND31, and the rest may be inferred, and switch SW 3Z is coupled between output terminal and the node ND3Z.Resistor ladder 24 is by one among turn-on switch component SW30～SW3Z, in order to output voltage V bg ' is carried out dividing potential drop, makes output voltage V bg " can be lower than output voltage V bg ', so that can operate in the low-voltage environment.In some embodiment, on-off element SW30 and SW3Z can be controlled by another resistance control signal from the external control device, make output voltage V bg " can be operated in the low-voltage environment.

When on-off element SW20～SW2M respectively has the input end (being high resistive path) that an end is coupled to operational amplifier OP, flow through on-off element SW20～SW2M to operational amplifier OP so do not have any electric current, so on-off element SW20～SW2M (transistor) can not influence the parameter of band gap reference circuits.Owing to there is not the electric current on-off element (transistor) of flowing through, therefore, even under the situation of considering the power rejection ratio, the influence of the characteristic that on-off element is different with hardware circuit, and on-off element is to be replaced by hardware circuit after obtaining optimum setting value, and the parameter of band gap reference circuits will still can not be affected.

Band gap reference circuits 10A, 20 and 30 is the necessary mac function that can play the part of in the operation of mixed mode integrated circuit or Analogous Integrated Electronic Circuits, for example data converter (data converter), phase-locked loop (PLL), oscillator, electric power management circuit, dynamic RAM (DRAM), flash memory (FLASH) ... or the like.For example, band gap reference circuits 30 provides output voltage V bg " to a core circuit, so that core circuit is carried out its function.

Though the present invention discloses as above with preferred embodiment; right its is not in order to limiting the present invention, anyly knows skill person, without departing from the spirit and scope of the present invention; when can doing a little change and retouching, so protection scope of the present invention is as the criterion when looking the claim person of defining.

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.

Images