CN102809979B - Third-order compensation band-gap reference voltage source - Google Patents

Abstract

The invention discloses a third-order compensation band-gap reference voltage source, which comprises a first PMOS (p-channel metal oxide semiconductor) tube, a first triode, a second triode, a third triode, a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor and a first amplifier. The reference voltage source disclosed by the invention provides a simple third-order compensation way, the current of the fourth resistor is PTAT (proportional to absolute temperature) current, and the voltage drop of the fourth resistor is increased along with the rising of the temperature, so that the current of the sixth resistor is also increased along with the rising of the temperature, the current of the fifth resistor is the sum of the current of the fourth resistor and the current of the sixth resistor, thus being equivalent to that the resistance of the fifth resistor is increased along with the rising of the temperature, i.e. the second-order item and the third-order item of VBE are compensated in such way, a conventional band-gap reference total framework does not need to be changed for the compensation way, a design process is simplified, and the cost is saved.

Description

Three-order compensation band gap reference voltage source

Technical Field

The invention belongs to the technical field of power supplies, and particularly relates to a design of a band-gap reference voltage source.

Background

High-precision voltage sources are widely used in integrated circuits, and are an indispensable part of many analog and hybrid circuits, such as analog-to-digital converters (ADCs), switching power supply technologies (DC-DC), and low dropout linear regulators (LDOs). In these circuits, the voltage source is used as a reference for comparison, and the precision of the voltage source directly influences the precision and the performance of the whole circuit.

In many circuits generating reference voltages, a bandgap reference has the advantages of small temperature coefficient, high power supply rejection ratio, high precision, compatibility with a CMOS process, and the like, and the specific principle is to obtain an output voltage with a small temperature coefficient by adding a voltage with a positive temperature coefficient and a voltage with a negative temperature coefficient. A conventional bandgap reference source is shown in FIG. 1 and comprises three field effect transistors M₁、M₂、M₃Three triodes Q₁、Q₂、Q₃(wherein Q)₂And Q₁Has an emitter area ratio of N), two resistors R₁、R₂And an operational amplifier A₁Composition, operational amplifier makes M by feedback₁、M₂The drain voltages of the tubes are equal, so that the resistance R is equal₁The voltages on are:

V_R1=V_BE1-V_BE2=V_TlnN=I_CR₁

in the above formula, V_TIs a thermal voltage, and is:

$V_T=\frac{\mathrm{KT}}{q}$

k is the thermodynamic normal temperature, T is the absolute temperature, and q is the electron charge amount.

Therefore:

$I_C=\frac{\mathrm{KT}}{\mathrm{qR}}$

output voltage:

V_OUT=I_CR₂+V_BE3

I_Cis proportional To temperature, called PTAT (proportional To Absolute temperature) current, has a positive temperature coefficient, I_CAnd R₂The multiplication results in a temperature-proportional voltage, which is used to compensate the voltage V with a negative temperature coefficient_BEThereby achieving a low temperature coefficient of the final output voltage, wherein V_BERepresenting the voltage difference between the emitter and the base of the triode.

In fact V_BENot only negative first order terms but also negative higher order terms exist, and the reference source in fig. 1 only considers the first order term, so that the temperature coefficient of the final output changes from positive to negative along with the rise of the temperature.

For the reasons, many secondary or high-order compensation structures are proposed, and a good effect is obtained, but the compensation structures are complicated, so that not only many resistors, transistors and other elements need to be added on the basis of the traditional bandgap reference source, but also a certain change needs to be made on the basic frame shown in fig. 1, and the difficulty and the cost of circuit design are increased.

Disclosure of Invention

The invention aims to solve the problem that the existing band-gap reference source is complex in structure, and provides a third-order compensation band-gap reference voltage source.

The technical scheme of the invention is as follows: a third order compensated bandgap reference voltage source comprising: the power supply circuit comprises a first PMOS (P-channel metal oxide semiconductor) tube, a first triode, a second triode, a third triode, a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor and a first amplifier, wherein the source electrode of the first PMOS tube is connected with an external power supply, the grid electrode of the first PMOS tube is connected with the output end of the first amplifier, and the drain electrode of the first PMOS tube is connected with the first terminal of the first resistor, the first terminal of the second resistor, the first terminal of the seventh resistor and the collector electrode of the third triode; the collector of the first triode is connected with the second terminal of the first resistor, the collector of the second triode is connected with the second terminal of the second resistor, the base of the first triode is connected with the base of the second triode and the second terminal of the seventh resistor and serves as the output end of the reference voltage source, the emitter of the second triode is connected with the first terminal of the third resistor, the emitter of the first triode is connected with the other end of the third resistor and is simultaneously connected with the first terminal of the fourth resistor, the second terminal of the fourth resistor is connected with the first terminal of the fifth resistor, the second terminal of the fifth resistor is connected with the ground potential, the positive input end of the first amplifier is connected with the collector of the second triode, and the negative input end of the first triode is connected with the collector of the triode; the base electrode of the third triode is connected with the emitting electrode of the first triode, the emitting electrode is connected with the first terminal of the sixth resistor, and the second terminal of the sixth resistor is connected with the first terminal of the fifth resistor.

The invention has the beneficial effects that: the third-order compensation band-gap reference voltage source provides a simple third-order compensation mode, the current of the fourth resistor is PTAT current, so the voltage drop of the fourth resistor increases along with the rise of temperature, the current of the sixth resistor also increases along with the rise of temperature, and the third resistor is connected with the fourth resistor in seriesThe current of the fifth resistor is the sum of the current of the fourth resistor and the current of the sixth resistor, which is equivalent to the resistance value of the fifth resistor increasing with increasing temperature, i.e. V is compensated in this way_BEThe compensation mode does not need to change the overall frame of the traditional band-gap reference, simplifies the design process and saves the cost.

Drawings

Fig. 1 is a schematic diagram of a conventional bandgap reference.

Fig. 2 is a structural framework diagram of the bandgap reference of the present invention.

Fig. 3 is a schematic diagram of an embodiment of a bandgap reference with a start-up circuit of the present invention.

Fig. 4 is a schematic diagram of the variation of the output reference voltage of the bandgap reference source with temperature according to the embodiment of the present invention.

Fig. 5 is a schematic diagram of the power supply rejection ratio of the output voltage of the bandgap reference source in the embodiment of the invention.

Detailed Description

The following further description is made with reference to the accompanying drawings and detailed description.

The band gap reference source provided by the invention realizes third-order compensation in a very simple mode, only needs to slightly change the structure of the traditional band gap reference source, only needs to add few components, is simple to realize, and can realize a better compensation effect. In order to make the objects, technical solutions and advantages of the present invention with respect to other reference voltages clearer, the present invention is described in further detail below with reference to the accompanying drawings.

FIG. 2 is a schematic structural diagram of a reference of the present invention, which specifically includes a bandgap reference portion and a compensation portion, wherein the bandgap reference portion includes a first PMOS M₁A first triode Q₁A second triode Q₂A first resistor R₁A second resistor R₂A third resistor R₃A fourth resistor R₄A fifth resistor R₅And an operational amplifier. M₁The source and the substrate of the transistor are connected with a power supply VDD, the grid is connected with the output of the operational amplifier, and the drain is connected with R₁And R₂One end of, QN₁Collector electrode of (2) is connected with R₁Another end of (1), Q₂Collector electrode of (2) is connected with R₂Another end of (1), Q₁Base of (2) is connected with Q₂Base electrode, Q₂Emitter connecting resistor R₃One end of, Q₁Is connected to R₃The other end is simultaneously connected with R₄One end of (A) R₄At the other end R₅One end of (A) R₅The other end of the operational amplifier is grounded, and the positive input end of the operational amplifier is connected with Q₂The negative input end of the collector is connected with Q₁The collector electrode of (1).

The compensation part comprises a third triode Q₃A sixth resistor R₆A seventh resistor R₇，Q₃Collector electrode of (2) is connected with M₁Drain terminal and base terminal of the transistor are connected with Q₁Emitter of (2), emitter node R₆One end of (A) R₆Is connected with the other end of R₄And R₅Point of intersection of (A), R₇One end of is connected with M₁The other end of the drain terminal is connected with Q₁The base of (1).

The specific compensation principle is as follows: flows through R₄Is linearly increased with increasing temperature, i.e. is a PTAT current, then R₄The voltage on will also increase with increasing current, and with R₄Increase of upper voltage, flowing through Q₃Will also increase, thereby causing a current to flow through R₅Is greater than the current flowing through R₄Is equivalent to R₅The value of (c) increases with increasing temperature. It can be seen that in this way, V is compensated_BEThe medium and negative high-order terms can realize the third-order compensation in a very simple mode.

R₇Is Q₁And Q₂Providing a base bias current, Q₃And R₆Composition ofCompensating body, Q at very low temperatures₃In the off state, so as with a conventional bandgap reference, R increases with temperature₄The obtained voltage gradually increases and flows through Q₃Also gradually increases:

flows through R₅Current of (2):

$I_{R_5}=I_{Q_3}+I_{R_4}$

I_Q3increase so that I_R5Increase, therefore R₅Actual effective value R₅(EFFECT) becomes:

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output voltage:

V_REF=V_BE+I_PTAT×R₅(EFFECT)

by increasing R₅(EFFECT) to compensate for V_BEThe third-order compensation is realized by only using two resistors and a triode, and compared with other compensation modes, the third-order compensation is simpler.

The band-gap reference source also comprises a starting circuit, and the starting output end of the starting circuit is connected with the output end of the reference voltage source.

FIG. 3 is a schematic diagram of an embodiment of a bandgap reference source with a start-up circuit including a second PMOS transistor M₂And the third PMOS transistor M₃First NMOS transistor M₄A second NMOS transistor M₅And the third NMOS transistor M₆And the fourth NMOS tube M₇Fourth triode Q₄And an eighth resistor R₈A ninth resistor R₉Wherein, the second PMOS transistor M₂The source electrode of the transistor is connected with an external power supply VDD, the grid electrode and the drain electrode are connected with a fourth triode Q₄Collector of (1), third PMOS transistor M₃The source electrode and the substrate of the transistor are connected with an external power supply VDD, and the grid electrode of the transistor is connected with a fourth triode Q₄The collector and the drain of the NMOS transistor are connected with the first NMOS transistor M₄Drain electrode of, M₄Is connected with the drain, the source and the substrate are grounded, the Mth₅Is connected to M₄The grid, the source and the substrate are grounded, and the drain is connected with M₆Of the grid electrode, M₆Source and Q of₄Is connected to and serves as a start-up output of the start-up circuit, M₆Drain electrode of (2) is connected with M₇Source electrode and substrate of (1) are grounded, M₇The grid and the drain of the transistor are connected with an external power supply VDD, the substrate is grounded, and R₉A first terminal of the NMOS transistor is connected with an external power supply VDD, a second terminal of the NMOS transistor is connected with a second NMOS transistor M₅A drain electrode of (1); fourth triode Q₄Emitter of (2) is connected with R₈First terminal of (2), R₈And the other end of the same is grounded.

When the starting circuit is just powered on, the starting circuit is started by M₆、M₇Providing current for the whole circuit, so that the whole circuit cannot work in a zero state; after the reference voltage is established, the reference voltage is generated by the baseThe quasi-generated current provides bias for the op-amp (I in fig. 3)_BIAS），R₉Is such that M is after the reference voltage is established₇And when the circuit is cut off, the starting circuit is turned off, and the operation of the reference is not influenced any more.

FIG. 4 is a graph showing the variation of output reference voltage with temperature, with a maximum variation of 0.67 millivolts at about 3.2ppm over the range of-60 to 120 degrees. More than ten ppm has been improved over the usual reference and only few components have been added, i.e. a third order compensation has been achieved in a simple manner.

Fig. 5 is a schematic diagram of the power supply rejection ratio of the output voltage, which is 63db higher than that of the conventional bandgap reference source at a frequency of 1 k.

It will be appreciated by those of ordinary skill in the art that the embodiments described herein are intended to assist the reader in understanding the principles of the invention and are to be construed as being without limitation to such specifically recited embodiments and examples. Those skilled in the art can make various other specific changes and combinations based on the teachings of the present invention without departing from the spirit of the invention, and these changes and combinations are within the scope of the invention.

Claims (1)

1. A third order compensated bandgap reference voltage source comprising: a first PMOS tube, a first triode, a second triode, a third triode, a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor and a first amplifier,

wherein,

the source electrode of the first PMOS tube is connected with an external power supply, the grid electrode of the first PMOS tube is connected with the output end of the first amplifier, and the drain electrode of the first PMOS tube is connected with the first terminal of the first resistor, the first terminal of the second resistor, the first terminal of the seventh resistor and the collector electrode of the third triode; the collector of the first triode is connected with the second terminal of the first resistor, the collector of the second triode is connected with the second terminal of the second resistor, the base of the first triode is connected with the base of the second triode and the second terminal of the seventh resistor and serves as the output end of the reference voltage source, the emitter of the second triode is connected with the first terminal of the third resistor, the emitter of the first triode is connected with the other end of the third resistor and is simultaneously connected with the first terminal of the fourth resistor, the second terminal of the fourth resistor is connected with the first terminal of the fifth resistor, the second terminal of the fifth resistor is connected with the ground potential, the positive input end of the first amplifier is connected with the collector of the second triode, and the negative input end of the first triode is connected with the collector of the triode; the base electrode of the third triode is connected with the emitting electrode of the first triode, the emitting electrode is connected with the first terminal of the sixth resistor, and the second terminal of the sixth resistor is connected with the first terminal of the fifth resistor;

the third-order compensation band gap reference voltage source also comprises a starting circuit, and the starting output end of the starting circuit is connected with the output end of the reference voltage source;

the starting circuit comprises a second PMOS tube, a third PMOS tube, a first NMOS tube, a second NMOS tube, a third NMOS tube, a fourth triode, an eighth resistor and a ninth resistor,

wherein,

the source electrode of the second PMOS tube is connected with an external power supply, and the grid electrode and the drain electrode of the second PMOS tube are connected with the collector electrode of the fourth triode; the source electrode and the substrate of the third PMOS tube are connected with an external power supply, the grid electrode of the third PMOS tube is connected with the collector electrode of the fourth triode, and the drain electrode of the third PMOS tube is connected with the drain electrode of the first NMOS tube; the grid electrode and the drain electrode of the first NMOS tube are connected, and the source electrode and the substrate are grounded; the grid of the second NMOS tube is connected with the first NMOS tube M₄The grid electrode, the source electrode and the substrate are grounded, and the drain electrode is connected with the grid electrode of the third NMOS tube; the source electrode of the third NMOS tube is connected with the grid electrode of the fourth triode and serves as the output end of the starting circuit, the drain electrode of the third NMOS tube is connected with the source electrode of the fourth NMOS tube, and the substrate is grounded; the grid and the drain of the fourth NMOS tube are connected with an external power supply, the substrate is grounded, the first terminal of the ninth resistor is connected with the external power supply, and the second terminal of the ninth resistor is connected with the drain of the second NMOS tube; and an emitter of the fourth triode is connected with a first terminal of the eighth resistor, and the other end of the eighth resistor is grounded.

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