CN203204485U - Band-gap reference circuit - Google Patents

Abstract

The utility model provides a band-gap reference circuit which comprises a first switch tube, a second switch tube, a third switch tube, a first transistor, a second transistor, a first resistor, a second resistor and an operational amplifier. Compared with an existing band-gap reference circuit, the operational amplifier is additionally arranged and forms a negative feedback loop with the first switch tube and the first resistor, so that the drain voltage of the first switch tube and the drain voltage of the second switch tube are maintained to be uniform, and the accuracy of the zero-temperature coefficient reference voltage output by the band-gap reference circuit is improved.

Description

A kind of band-gap reference circuit

Technical field

The utility model relates to electronic circuit field, relates in particular to a kind of band-gap reference circuit.

Background technology

Band-gap reference circuit is used for realizing output zero-temperature coefficient reference voltage, namely exports temperature independent constant voltage.Have a kind of band-gap reference circuit now as shown in Figure 1, this circuit is to utilize M1 and two PMOS pipes of M2 to form current mirror, flows through same current, thereby keeps the drain voltage of M1 and M2 to equate.But sample such scheme, because the second-order effects of metal-oxide-semiconductor, such as channel-length modulation, it is larger that the drain voltage of M1 and M2 often differs, performance can be a greater impact, and the zero-temperature coefficient reference voltage of band-gap reference circuit output is inaccurate, and its temperature coefficient is non-vanishing or non-constant.

The utility model content

The utility model provides a kind of band-gap reference circuit for addressing the above problem, and this circuit output has the reference voltage of zero-temperature coefficient and voltage constant.

The utility model provides a kind of band-gap reference circuit, comprising: the first switching tube of common gate and common source, second switch pipe and the 3rd switching tube, and its common source connects power supply; Common emitter and grounded base the first transistor and transistor seconds, its common emitter and common base earth, the collector of described the first transistor is connected through the drain electrode of the first resistance with the first switching tube, the collector of described transistor seconds is connected with the drain electrode of second switch pipe, the two ends of the second resistance are connected with the drain electrode of second switch pipe with the 3rd switching tube respectively, the drain electrode output reference voltage of described the 3rd switching tube, and operational amplifier, the negative-phase input of described operational amplifier is connected with the drain electrode of second switch pipe and the collector of transistor seconds, the normal phase input end of described operational amplifier is connected with the drain electrode of the first switching tube and the collector of the first transistor, the output terminal of described operational amplifier and the first switching tube, the grid of second switch pipe and the 3rd switching tube connects.

Preferably, described band-gap reference circuit also comprises the 3rd transistor that several are in parallel with described the first transistor.

Preferably, described the first switching tube, second switch pipe and the 3rd switching tube are the PMOS pipe.

Preferably, described the first transistor, transistor seconds and the 3rd transistor are double pole triode.

The utility model provides a kind of band-gap reference circuit, increased by an operational amplifier with respect to existing band-gap reference circuit, itself and the first switching tube and the first resistance form feedback loop, the drain voltage of the first switching tube and the drain voltage of second switch pipe are consistent, have improved the accuracy of the reference voltage of band-gap reference circuit output.

Description of drawings

Fig. 1 is the band-gap reference circuit figure of prior art;

Fig. 2 is band-gap reference circuit figure of the present utility model.

Embodiment

Clearer for technical matters, technical scheme and beneficial effect that the utility model is solved, below in conjunction with drawings and Examples, the utility model is further elaborated.Should be appreciated that specific embodiment described herein only in order to explaining the utility model, and be not used in restriction the utility model.

The band-gap reference circuit figure of Fig. 1 prior art, wherein M1, M2 are PMOS pipe, M1, M2 form current mirror, in theory its branch current at place is equal separately, i.e. also approximately equal of the drain terminal voltage of the drain terminal voltage of M1 and M2.At this moment, resistance R ₁On voltage difference can be similar to be expressed as V _BE2-V _BE1, V _BE1Refer to the base stage of double pole triode Q1 and the voltage between the emitter, V _BE2Refer to the base stage of double pole triode Q2 and the voltage between the emitter.The number of Q2 is that the number of 1, Q1 is M, and M Q1 is in parallel; PMOS pipe M3 also forms current mirror with M1, and enlargement factor is N, and electric current passes through resistance R ₂Flow into Q2.Such R ₁On electric current be Its derivation is as follows:

Resistance R ₁Upper electric current is

$V_{\mathrm{BEI}}=V_T\ln \left(\frac{I}{M\×I_S}\right),$

I is the electric current that flows into double pole triode emitter-base bandgap grading end.I _SRefer to the saturation current of double pole triode; V _TThermal constant, (V _T=KT/q, K refers to Boltzmann constant, T refers to temperature, q is electron charge).

V _BE1And V _BE2The above-mentioned resistance R of expression formula substitution ₁Current expression in, obtain resistance R ₁On electric current be

On this basis, easily obtain V _OutExpression formula:

Be that existing band-gap reference output voltage is expressed formula.Because V _BE2Can think the forward voltage of the diode that PN junction forms, so V _BE2Negative temperature coefficient, and

It is positive temperature coefficient (PTC).Therefore, by Rational choice N, the M value and

Ratio can allow V _OutTemperature coefficient be zero, i.e. V _OutConstant and the variation with temperature and changing not of the magnitude of voltage of output.

But in actual applications, the M1 in the above-mentioned band-gap reference circuit and M2 are because of the second-order effects of metal-oxide-semiconductor, and such as channel-length modulation, it is larger that the drain voltage of M1 and M2 often differs, often its output reference voltage V _OutTemperature coefficient non-vanishing.

For the problems referred to above, the utility model provides a kind of band-gap reference circuit, as shown in Figure 2, comprising: the first switching tube M1, the second switch pipe M2 of common gate and common source and the 3rd switching tube M3, and its common source meets power vd D; Common emitter and grounded base the first transistor Q1 and transistor seconds Q2, its common emitter and common base earth, the collector of the first transistor Q1 is connected with the drain electrode of the first switching tube M1 through the first resistance R 1, the collector of transistor seconds Q2 is connected with the drain electrode of second switch pipe M2, the two ends of the second resistance R 2 are connected with the drain electrode of second switch pipe M2 and the 3rd switching tube M3 respectively, the drain electrode output zero-temperature coefficient reference voltage V of the 3rd switching tube M3 _OutAnd operational amplifier A MP, the negative-phase input of described operational amplifier A MP is connected with the drain electrode of second switch pipe M2 and the collector of transistor seconds Q2, the normal phase input end of described operational amplifier A MP is connected with the drain electrode of the first switching tube M1 and the collector of the first transistor Q1, and the output terminal of described operational amplifier A MP is connected with the grid of the first switching tube M1, second switch pipe M2 and the 3rd switching tube M3.

The band-gap reference circuit that the utility model provides, increased by an operational amplifier A MP with respect to existing band-gap reference circuit, itself and the first switching tube M1 and the first resistance R 1 form feedback loop, regulate the drain voltage of the first switching tube M1 and the drain voltage of second switch pipe M2 by operational amplifier A MP, it is consistent, has improved the reference voltage V of band-gap reference circuit output _OutAccuracy so that reference voltage V _OutTemperature coefficient be zero.

As the preferred version of the present embodiment, described band-gap reference circuit also comprises the 3rd transistor that several are in parallel with described the first transistor Q1, does not draw among the 3rd transistor figure; Preferably, described the first switching tube M1, second switch pipe M2 and the 3rd switching tube M3 are the PMOS pipe, and described the first transistor Q1, transistor seconds Q2 and the 3rd transistor are double pole triode.

For the technical solution of the utility model is more readily understood, below the principle of work of brief description band-gap reference circuit shown in Figure 2.Operational amplifier A MP among the figure and the first switching tube M1, the first resistance R 1 forms feedback loop, when the drain voltage of the drain voltage of the first switching tube M1 and second switch pipe M2 is inconsistent, the pressure reduction of these two drain electrode ends is amplified in operational amplifier A MP output, this pressure difference signal is as the input signal of the one-stage amplifier of the first switching tube M1 and the first resistance R 1 composition, this pressure difference signal is through the first switching tube M1, the first resistance R 1, the one-stage amplifier that the first transistor Q1 forms is exaggerated, its Output rusults feeds back to the drain electrode of the first switching tube M1, be equivalent to oppositely calibrate the pressure reduction of the drain voltage of the drain voltage of the first switching tube M1 and second switch pipe M2, so that the drain voltage of the first switching tube M1 is consistent with the drain voltage of second switch pipe M2.Simultaneously, also have positive feedback in this circuit, but because the output impedance of the drain electrode end of the first switching tube M1 greater than the output impedance of the drain electrode end of second switch pipe M2, gains greater than positive feedback so negative feedback gains, i.e. degenerative effect is better than positive feedback.

The above only is preferred embodiment of the present utility model; not in order to limit the utility model; all any modifications of within spirit of the present utility model and principle, doing, be equal to and replace and improvement etc., all should be included within the protection domain of the present utility model.

Claims (4)

1. band-gap reference circuit comprises: the first switching tube of common gate and common source, second switch pipe and the 3rd switching tube, and its common source connects power supply; Common emitter and grounded base the first transistor and transistor seconds, its common emitter and common base earth, the collector of described the first transistor is connected through the drain electrode of the first resistance with the first switching tube, the collector of described transistor seconds is connected with the drain electrode of second switch pipe, the two ends of the second resistance are connected with the drain electrode of second switch pipe with the 3rd switching tube respectively, the drain electrode output reference voltage of described the 3rd switching tube, it is characterized in that, also comprise operational amplifier, the negative-phase input of described operational amplifier is connected with the drain electrode of second switch pipe and the collector of transistor seconds, the normal phase input end of described operational amplifier is connected with the drain electrode of the first switching tube and the collector of the first transistor, the output terminal of described operational amplifier and the first switching tube, the grid of second switch pipe and the 3rd switching tube connects.

2. band-gap reference circuit as claimed in claim 1 is characterized in that, also comprises the 3rd transistor that several are in parallel with described the first transistor.

3. band-gap reference circuit as claimed in claim 1 or 2 is characterized in that, described the first switching tube, second switch pipe and the 3rd switching tube are the PMOS pipe.

4. band-gap reference circuit as claimed in claim 1 or 2 is characterized in that, described the first transistor, transistor seconds and the 3rd transistor are double pole triode.

Images