CN202133922U

CN202133922U - Reference voltage circuit

Info

Publication number: CN202133922U
Application number: CN201020688509U
Authority: CN
Inventors: 黄立朝
Original assignee: Wuxi China Resources Semico Co Ltd
Current assignee: Wuxi China Resources Semico Co Ltd
Priority date: 2010-12-29
Filing date: 2010-12-29
Publication date: 2012-02-01
Anticipated expiration: 2020-12-29

Abstract

The utility model discloses a reference voltage circuit comprising a current source, an operational amplifier, a transistor and a resistance. An input voltage can be respectively input into a base electrode of a first transistor and a base electrode of a second transistor. A collector of the first transistor is connected with a positive input terminal of an amplifier, and is connected with a current source through a second resistance. An emitter electrode of the second transistor is grounded through a third resistance, and a collector of the second transistor is connected with a negative input terminal of the amplifier, and is connected with the current source through the first resistance. The output end of the amplifier is connected with the output ends of a reference voltage, the current source and the amplifier. The third resistance is a high resistance square resistance.

Description

A kind of reference voltage circuit

Technical field

The utility model belongs to the IC design field, is specifically related to a kind of reference voltage circuit, relates in particular to a kind of bandgap voltage reference circuit.

Background technology

Band-gap reference is most popular a kind of in all reference voltages; Because it has and the almost irrelevant outstanding advantage of supply voltage, technology, temperature variation, so be widely used in high-precision comparer, A/D or D/A converter, LDO voltage stabilizer and other the many Analogous Integrated Electronic Circuits.The main effect of band-gap reference is reference voltage or the reference current that in integrated circuit, provides stable, and this just requires benchmark insensitive to the variation and the variation of temperature of supply voltage.

Schematic diagram and the utility model bandgap voltage reference circuit diagram shown in Figure 1 that the tradition bandgap voltage reference produces are similar, wherein calculate reference voltage V _RefFormula is following:

In theory, reference voltage value Vref only depends on the area ratio of ratio and the triode of R2 and R3, and is irrelevant with other factors.After choosing suitable resistance, be 2.24K Ω like R2, R3 is 80 Ω, the above-mentioned formula of substitution can draw reference voltage value Vref=2.4V.Amplify through ratio then, obtain the external benchmark of 3.5V.

But, because the emitter resistance Re in the NPN model is bigger than normal, with resistance value under 4 times of pipes can analogy; Micro-current source can not form; And become proportion current source (the former design resistance of R3 is 80 ohm, and the resistance of the emitter resistance Re of NPN pipe T1 is about 40 ohm, has been in the same order of magnitude); The current potential of two input ends of difference amplification is no longer consistent, causes benchmark no longer stable.

The parameters simulation result who extracts according to existing sample circuit is shown in Figure 2, can find out that from simulation result power supply scans from 0～8V; Benchmark just begins to stablize after power supply is higher than about 5.3V; And about stationary value 4.4V, bigger from design theory value 3.55V gap, can not meet the demands.

The utility model content

Because the problems referred to above that prior art exists, the utility model proposes a kind of reference voltage circuit, and it can effectively solve the problem that prior art exists.

To achieve these goals, the utility model proposes a kind of reference voltage circuit, comprises current source, operational amplifier, transistor and resistance,

Input voltage inputs to the base stage of the first transistor, transistor seconds respectively;

The collector of the first transistor is connected to the normal phase input end of amplifier, and links to each other with current source through second resistance;

The emitter of transistor seconds is through the 3rd resistance eutral grounding, and the collector of transistor seconds is connected to the negative input of amplifier, and links to each other with current source through first resistance;

The output terminal of amplifier links to each other with amplifier out with current source with reference voltage;

Wherein, first resistance, second resistance, the 3rd resistance are all the high resistant square resistance.

Further, the Standard resistance range of first resistance, second resistance, the 3rd resistance is respectively 89.6K Ω-112K Ω, 89.6K Ω-112K Ω, 3.2K Ω-4K Ω.

The utility model is through improving the resistance of emitter degeneration resistance; Reduced the excessive negative effect that the formation of band-gap reference is caused of NPN pipe emitter resistance Re effectively; Make circuit not do under the prerequisite of change in basic structure, process conditions; Successful realization the expection the band-gap reference characteristic, made things convenient for the smooth research and development of circuit greatly, improved the compatibility of technology.

Description of drawings

Fig. 1 is the utility model bandgap voltage reference circuit diagram;

Fig. 2 is the voltage parameter analogous diagram of existing bandgap voltage reference circuit;

Fig. 3 is the voltage parameter analogous diagram of the bandgap voltage reference circuit of the utility model;

Fig. 4 is the temperature scanning analogous diagram of the bandgap voltage reference circuit of the utility model;

Fig. 5 is the temperature and the magnitude of voltage comparison diagram of the bandgap voltage reference circuit of the utility model;

Fig. 6 is the circuit voltage parameters simulation figure of bandgap voltage reference circuit under different emitter resistance values of the utility model.

Embodiment

Combine accompanying drawing at present, the embodiment of the utility model done further to specify:

The utility model is when the bandgap voltage reference circuit design, and circuit diagram is as shown in Figure 1, and the associated electrical resistance that forms benchmark is strengthened, and makes it enough big with respect to the emitter resistance Re of NPN, to such an extent as to can ignore the influence of emitter resistance Re.Through increasing the R3 resistance, can offset the excessive negative effect that causes of NPN pipe emitter resistance Re, increase R1, R2 resistance simultaneously and then be and guarantee the reference voltage that obtains expecting.

In first embodiment of the utility model, take fairly simple method, be exactly that direct resistance with R1, R2, the several resistance of R3 increases, increase to more than 40 times of original resistance.Such as, originally the resistance of R1, R2, R3 is 2.24K Ω, 2.24K Ω, 80 Ω; Value scope after improving now is respectively 89.6K Ω-112K Ω, 89.6K Ω-112K Ω, 3.2K Ω-4K Ω.

In second embodiment of the utility model, can change the resistance type of R1, R2, R3 into the high resistant square resistance by the low-resistance square resistance.If the type of resistance R 1, R2, R3 is directly become the high resistant type from the low-resistance type; The size of resistance will not have big change in circuit design so; Laying out pattern does not need to change; Do not do in circuit basic structure, process conditions under the prerequisite of change, reach the band-gap reference characteristic of expection.

According to the bandgap voltage reference circuit of the utility model, when the value of choosing R1, R2, R3 was 98K Ω, 98K Ω and 3.5K Ω, its voltage parameter simulation result was as shown in Figure 3.Power supply begins up at 4.5V from 0～8V scanning, and baseline stability is about 3.5V.

The simulation result of Fig. 2 and Fig. 3 is to recently seeing, before circuit was not changed, benchmark just began to stablize after power supply is higher than about 5.3V, and can not meet the demands about stationary value 4.4V.And after the circuit improvement, begin up at 4.5V, baseline stability is about 3.5V.This meets the result of the design theory value 3.55V of primary circuit fully.In addition, satisfy in the working range 4.5～5.5V of supply voltage the requirement of baseline stability.

Simultaneously, the circuit after improving is done temperature scanning emulation, the result is as shown in Figure 4.The concrete numerical value that records the corresponding reference voltage of temperature is as shown in the table:

Temperature (Celsius)	Reference voltage (V)
		-25	3.56
-10	3.56
		0	3.55
10	3.55
		20	3.55
30	3.54
		40	3.54
50	3.53
		60	3.52
70	3.52
		80	3.51

90

3.5

Fig. 5 is temperature and the magnitude of voltage comparison diagram that plots according to the numerical value in the last table, once can see between working temperature (20～70 ℃) every variation, and reference voltage changes about 0.0004V, reaches the characteristic of bandgap voltage reference circuit.

Fig. 6 is the circuit voltage parameters simulation figure of bandgap voltage reference circuit under different emitter resistance values of the utility model.For the inaccurate situation of emitter resistance Re in the emulation NPN model occurs; We have done the emulation of circuit under the different situations of emitter resistance Re; The result is following: from simulation result, the data of middle graph are that the utility model improves the circuit simulation data, and Re changes from 0.01 times to 1 times; Benchmark changes between 3.55～3.58V, satisfies the requirement of baseline stability.The data of the right figure are the situation of change of the benchmark of existing sample circuit with Re, can find out that when Re reduced gradually, benchmark also was the design theory value that moves closer to 3.55V.This has verified from another point of view also that under the situation that Re can not adjust the utility model is feasible to the improvement project of resistance.

But above-mentioned embodiment is exemplary, is to be the restriction that this patent is comprised scope in order better to make those skilled in the art can understand this patent, can not to be interpreted as; So long as according to spirit that this patent discloses done anyly be equal to change or modify, all fall into the scope that this patent comprises.

Claims

1. a reference voltage circuit comprises current source, and operational amplifier, transistor and resistance is characterized in that:

Wherein, the 3rd resistance is the high resistant square resistance.

2. reference voltage circuit according to claim 1 is characterized in that: first resistance and second resistance are all the high resistant square resistance.

3. reference voltage circuit according to claim 1 and 2 is characterized in that: the Standard resistance range of first resistance, second resistance, the 3rd resistance is respectively 89.6K Ω-112K Ω, 89.6K Ω-112K Ω, 3.2K Ω-4K Ω.