Band-gap reference source high-order curvature compensation method based on operational amplifier

Abstract

The invention discloses a band-gap reference source high-order curvature compensation method based on an operational amplifier, and belongs to the technical field of high-precision analog integrated circuit design, and the method comprises the steps: generating an absolute temperature proportion PTAT current and an absolute temperature complementary CTAT current; generating a high-order curvature compensation voltage based on the PTAT current and the CTAT current; amplifying the generated high-order curvature compensation voltage through an operational amplifier, and superposing the amplified high-order curvature compensation voltage to a band-gap reference output stage to obtain compensated band-gap reference output voltage; and carrying out band-gap reference output calibration on the compensated band-gap reference output voltage so as to ensure that the temperature drift coefficient of the output band-gap reference voltage in the preset temperature range is smaller than a preset threshold value. According to the invention, high-order elimination of base-emitter voltage nonlinearity can be realized in a wide temperature range, and a relatively low temperature coefficient and low noise are achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of high-precision analog integrated circuit design, in particular to a high-order curvature compensation method for a bandgap reference source based on an operational amplifier. BACKGROUND

[0002] A bandgap reference circuit is a key component of modern integrated circuits, which is widely used to generate a stable reference voltage or current, so as to be not affected by temperature, power supply voltage variation and manufacturing process deviation. The bandgap reference circuit is more important in precision circuit applications such as analog-to-digital converters (ADCs), digital-to-analog converters (DACs), power management circuits and other circuits requiring reliable reference voltages.

[0003] In order to meet the specific application requirements, the design of the bandgap reference needs to consider multiple aspects. Some typical aspects of the bandgap reference design include considering power consumption, operating voltage, precision, etc. For these important indicators, designers have also designed bandgap reference sources with excellent performance. One of the most important design considerations for a bandgap reference power supply is its temperature coefficient. At present, with the continuous development of semiconductor technology and electronic circuit technology, people need a bandgap reference source that can work more stably in a wider temperature range, which also puts higher test on the temperature drift coefficient of the bandgap reference. The traditional bandgap reference circuit mainly realizes zero temperature drift coefficient at a single temperature by directly combining the proportional-to-absolute temperature (PTAT) voltage and the complementary-to-absolute temperature (CTAT) voltage. This method can only cancel the first-order temperature drift coefficient of the voltage, while ignoring the high-order components existing in the source emitter voltage V BE The output voltage still has a small curvature and thereby affects the temperature drift coefficient. The temperature drift coefficient of the general bandgap reference source cannot meet the application requirements in some high-precision scenarios. SUMMARY

[0004] The present application provides a high-order curvature compensation method for a bandgap reference source based on an operational amplifier, to solve the technical problem that the temperature drift coefficient of the bandgap reference source cannot meet the application requirements in high-precision scenarios in the existing bandgap reference circuit design, and to improve the performance of the bandgap reference source.

[0005] To solve the above technical problems, the present application provides the following technical solutions: A high-order curvature compensation method for a bandgap reference source based on an operational amplifier Generate a proportional-to-absolute temperature (PTAT) current and a complementary-to-absolute temperature (CTAT) current; Based on the PTAT current and the CTAT current, generate a high-order curvature compensation voltage; The generated high-order curvature compensation voltage is amplified by an operational amplifier, and the amplified high-order curvature compensation voltage is superimposed on a bandgap reference output stage to obtain a compensated bandgap reference output voltage. The compensated bandgap reference output voltage is calibrated to ensure that the output bandgap reference voltage temperature drift coefficient is less than a preset threshold within a preset temperature range.

[0006] Further, the absolute temperature proportional PTAT current and the absolute temperature complementary CTAT current are generated, including: The PTAT current and the CTAT current are generated by a double operational amplifier current mode bandgap reference circuit.

[0007] Further, the parallel ratio of the bipolar transistors in the double operational amplifier current mode bandgap reference circuit is 1: M ; then the generated PTAT current and the CTAT current The expressions are respectively:

[0008]

[0009] , wherein is the thermal voltage of the bipolar transistor in the double operational amplifier current mode bandgap reference circuit; is the resistance value connected in series between the emitters of the two bipolar transistors, is the resistance value connected in parallel between the collector and the emitter of the bipolar transistor; is the base-emitter voltage of the bipolar transistor.

[0010] Further, based on the PTAT current and the CTAT current, a high-order curvature compensation voltage is generated, including: The PTAT current and the CTAT current are copied out of the double operational amplifier current mode bandgap reference circuit to a high-order curvature compensation circuit module by a common-source common-gate current mirror; wherein the high-order curvature compensation circuit module includes a first bipolar transistor and a second bipolar transistor of NPN type arranged in parallel, and the parallel ratio of the first bipolar transistor and the second bipolar transistor is set to 1: Q ; and the emitter of the second bipolar transistor is connected to the emitter of the first bipolar transistor through an N-channel field effect transistor; In the high-order curvature compensation circuit module, the PTAT current and the CTAT current are input to the first bipolar transistor and the second bipolar transistor arranged in parallel in a certain ratio; then the required high-order curvature compensation voltage is generated at the drain of the N-channel field effect transistor.

[0011] Further, the PTAT current and the CTAT current are input to the first bipolar transistor and the second bipolar transistor arranged in parallel according to a certain ratio, comprising: The first bipolar transistor inputs the PTAT current with a first preset input ratio; The second bipolar transistor inputs the PTAT current with a second preset input ratio and the CTAT current.

[0012] Further, the high-order curvature compensation voltage The expression is as follows:

[0013] Wherein, is the base-emitter voltage of the first bipolar transistor; is the base-emitter voltage of the second bipolar transistor; T is the temperature at which the circuit is located; is the Boltzmann constant; is the electronic charge; is the preset reference temperature.

[0014] Further, the expression of the compensated bandgap reference output voltage is as follows:

[0015] Wherein, is the base-emitter voltage of the bipolar transistor in series with the output reference voltage of the output stage; is the high-order curvature compensation voltage; is the amplification multiple of the high-order curvature compensation voltage; is the output resistance of the bandgap reference voltage output circuit; is the PTAT current.

[0016] Further, for the compensated bandgap reference output voltage, bandgap reference output calibration is performed to ensure that the bandgap reference voltage temperature drift coefficient is less than a preset threshold in a preset temperature range, comprising: A change curve of the compensated bandgap reference output voltage in a temperature range of-40 to 125 degrees Celsius is drawn; Based on the change curve, the bandgap reference voltage temperature drift coefficient is calculated; According to the bandgap reference voltage temperature drift coefficient, the input ratio of the PTAT current in the high-order curvature compensation circuit module is adjusted to ensure that the bandgap reference voltage temperature drift coefficient is less than the preset threshold in the preset temperature range.

[0017] The technical scheme provided by the application has at least the following beneficial effects: The application can effectively improve the precision of the bandgap reference source, reduce the temperature drift coefficient, and has the characteristics of high precision, simple structure and low power consumption, and can be widely applied in high-precision analog integrated circuits requiring high-precision voltage reference, and improve the overall precision and universality of the circuit. BRIEF DESCRIPTION OF DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0019] Figure 1 is the execution flow diagram of the high-order curvature compensation method of the bandgap reference source based on the operational amplifier provided by the embodiment of the present application; Figure 2 is the circuit principle diagram of the bandgap reference core circuit for generating PTAT and CTAT currents; Figure 3 is the circuit principle diagram of the circuit for generating high-order curvature compensation voltage, amplifying and superimposing output; Figure 4 is the circuit principle diagram of the curvature calibration circuit provided by the embodiment of the present application. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical scheme and advantages of the present application more clear, the embodiments of the present application will be further described in detail below with reference to the drawings.

[0021] First of all, it should be noted that in the embodiments of the present application, the words such as "exemplarily", "for example" are used to represent as an example, illustration or explanation. Any embodiment or design scheme described as "exemplary" in the present application should not be interpreted as more preferred or more advantageous than other embodiments or design schemes. Rather, the word "exemplarily" is intended to present the concept in a specific way. In addition, in the embodiments of the present application, the meaning expressed by "and / or" can be both, or can be one of the two.

[0022] First embodiment

[0023] The embodiment provides a high-order curvature compensation method of a bandgap reference source based on an operational amplifier for a bandgap reference source, and relates to reference generation and precision improvement of a bandgap reference source in a high-precision analog circuit. The method is used for improving the performance of the bandgap reference source. The execution flow of the method is as shown in Figure 1 The method comprises the following steps: S1, generating an absolute temperature proportional PTAT current and an absolute temperature complementary CTAT current; Specifically, the embodiment generates PTAT and CTAT currents by a dual operational amplifier current mode bandgap reference circuit, wherein the PTAT current The expression is:

[0024] CTAT current The expression is:

[0025] wherein, is a thermal voltage of an NPN type bipolar transistor (BJT) in the dual operational amplifier current mode bandgap reference circuit; is a resistance value connected in series between the two bipolar transistors, is a resistance value connected in parallel between the collector and the emitter of the bipolar transistor, M is the number of BJTs connected in parallel in the dual operational amplifier current mode bandgap reference circuit, is a base-emitter voltage of the BJT.

[0026] S2, generating a high-order curvature compensation voltage based on the PTAT current and the CTAT current; Specifically, the embodiment generates the high-order curvature compensation voltage in the following manner: The cascode current mirror structure is used to copy the two-way PTAT current and CTAT current to the high-order curvature compensation circuit module from the current mode bandgap reference circuit, and the PTAT current and the CTAT current are input to a pair of BJTs with a parallel ratio of 1: Q The specific current input method is that the BJT with a parallel number of 1 flows a certain proportion of the PTAT current, and the BJT with a parallel number of Q flows a certain proportion of the PTAT and CTAT currents at the same time; and the BJT with a parallel number of Q The emitter of the BJT with a parallel ratio of Q is connected to the emitter of another BJT through an N-channel MOS (NMOS), and the high-order curvature compensation voltage required at the drain of the NMOS, i.e., the emitter of the BJT with a parallel ratio of The expression is:

[0027] wherein, is the Boltzmann constant, is the electronic charge, is the reference temperature; the base-emitter voltage of the BJT in parallel number the base-emitter voltage of the BJT in parallel number Q the base-emitter voltage of the BJT in parallel number T the temperature at which the circuit is located.

[0028] S3, the generated high-order curvature compensation voltage is amplified through an operational amplifier, and the amplified high-order curvature compensation voltage is superimposed to the bandgap reference output stage to obtain the compensated bandgap reference output voltage; Specifically, the generated high-order curvature compensation voltage is amplified several times through an operational amplifier, and the output voltage is connected to the BJT collector of the bandgap reference voltage output branch. The output branch current is the PTAT current generated by the current mirror replication. Then the final output bandgap reference voltage is The expression is:

[0029] wherein, the base-emitter voltage of the bipolar transistor in series with the output reference voltage the output stage of the output reference voltage; the voltage amplification ratio finally generated by the operational amplifier, that is, the amplification multiple of the high-order curvature compensation voltage, the output resistance of the bandgap reference voltage output circuit, the PTAT current.

[0030] S4, the bandgap reference output calibration is performed on the compensated bandgap reference output voltage to ensure that the output bandgap reference voltage temperature drift coefficient is less than the preset threshold value in the preset temperature range. Specifically, the bandgap reference output calibration is performed in the following manner: according to the voltage change curve of the last output voltage in the temperature range of-40-125 degrees Celsius, the bandgap reference voltage temperature drift coefficient is calculated. According to the temperature drift coefficient, the size proportion of the aforementioned PTAT current is fine-tuned to ensure that the output bandgap reference voltage temperature drift coefficient is less than 1ppm / ℃ in a wide temperature range.

[0031] In summary, the embodiment provides an operational amplifier-based high-order curvature compensation method for a bandgap reference source. The main design goal is to achieve a temperature coefficient T C<1ppm / ℃, namely the bandgap reference source with high temperature stability. The method innovatively uses an operational amplifier to collect and amplify the high-order curvature voltage generated by two different temperature coefficient currents, which can generate a reference voltage with a lower temperature coefficient at the output stage. Thus, the precision of the bandgap reference source is effectively improved, the temperature drift coefficient is reduced, and the bandgap reference source has the characteristics of high precision, simple structure, and low power consumption. The bandgap reference source can be widely applied to high-precision analog integrated circuits requiring high-precision voltage references, and can improve the overall precision and universality of the circuit.

[0032] Second embodiment

[0033] The embodiment combines the drawings and specific examples to illustrate the implementation process of the method of the application, and specifically includes: I. Absolute temperature proportional (PTAT) current and absolute temperature complementary (CTAT) current generation.

[0034] Specifically, the embodiment adopts a double-operational-amplifier current-mode bandgap reference core circuit with a structure similar to the traditional current-mode bandgap circuit structure as shown in Figure 2 , to generate PTAT and CTAT currents. The core circuit adopts a double-operational-amplifier structure, which can separate the PTAT and CTAT currents and copy them to the subsequent circuit through a cascode current mirror. The use of the cascode current mirror can improve the power supply rejection ratio (PSRR) of the circuit and help improve the circuit performance. In the circuit, the number of parallel bipolar junction transistors (BJTs) is 8, which helps to complete the layout matching of the BJT. Thus, the PTAT current can be represented as: M

[0035] Correspondingly, the CTAT current can be represented as:

[0036] wherein, and The size depends on the matching of the first-order temperature coefficient of the current. In the embodiment, the size of the first-order temperature coefficient of the current can be taken as 12 , , The size of the first-order temperature coefficient of the current is about 150 , and the PTAT and CTAT currents generated at a temperature of 300 are both about 4.5 .

[0037] II. High-order curvature compensation voltage generation.

[0038] Specifically, as shown in Figure 3 ​As shown, the embodiment respectively passes the PTAT current generated in the first step and the ZTAT current with a temperature coefficient of about zero obtained by adding the PTAT current and the CTAT current through the cascode current mirror into a group of NPN type BJTs, denoted as and , the parallel number of is 4; and the bases are connected, the collector is connected to the cascode current mirror passing the PTAT current, the collector is connected to the cascode current mirror passing the ZTAT current, the emitter is grounded, the emitter is connected to an N-channel field effect transistor (NMOS) and the emitter is connected, the drain is connected to the emitter, the source is connected to the emitter, the gate is connected to the collector; in order to adjust the collector voltage, the collector is connected in series with a diode-connected NMOS denoted as , the gate and the drain are connected to the cascode current mirror, and the source is connected to the collector; in order to adjust and the base voltage, and the base is connected to an NMOS denoted as the source, the drain is connected to the power supply voltage, and the gate is connected to the drain; the specific current input method is: one-fifth of the PTAT current, about 0.9 , a certain proportion of the PTAT and CTAT currents, the proportion of the CTAT current to the PTAT current is 3 / 25, and each is about 0.54 ; the drain can generate the required high-order curvature compensation voltage, wherein the curvature compensation voltage is expressed as:

[0039] wherein the reference temperature is 300 .

[0040] 3. High-order curvature compensation voltage superposition.

[0041] Specifically, if Figure 3 As shown, in this embodiment, the curvature compensation voltage After the input is amplified several times by the operational amplifier, the output voltage is connected to the BJT of the bandgap reference voltage output branch (denoted as ) collector, the current flowing into the output branch is the PTAT current generated by the current mirror copy, and finally the output bandgap reference voltage is expression:

[0042] In this embodiment, The value is 2. The value is about 145 , The general value is about 3.05 , so the output reference voltage can be obtained About 1.25 .

[0043] 4. Bandgap reference output calibration.

[0044] It should be noted that when performing the first high-order compensation, a relatively accurate reference voltage can theoretically be generated. However, due to process deviations and device aging that may occur in chip production, a calibration module needs to be added to the compensation circuit to ensure that the chip can always maintain a high level of accuracy. Figure 3 The adjustable PTAT current sources shown are all calibrated current sources. This current source can also be regarded as a current DAC, that is, a current steering digital-to-analog converter, whose structure is as follows Figure 4 As shown in the figure, the bandgap reference voltage temperature drift coefficient can be calculated based on the final output voltage variation curve within the temperature range of -40-125 degrees Celsius. Based on this temperature drift coefficient, the aforementioned PTAT current ratios can be fine-tuned by calibrating the current source to ensure that the output bandgap reference voltage temperature drift coefficient is less than 1ppm / °C over a wide temperature range.

[0045] Furthermore, it is to be understood that the phraseology or terminology such as "first" and "second" etc. is used by way of example, and is merely intended to distinguish one

[0046] Finally, it is to be understood that the above description is only a preferred embodiment of the application, and that modifications and / or improvements can be incorporated, without departing from the scope of the application as defined in the following claims. Therefore, the following claims are intended to be interpreted to include preferred embodiments and all modifications and alterations, and are intended to cover all equivalents falling within the scope of the application.

Claims

1. A method for compensating high-order curvature of a bandgap reference source based on an operational amplifier, characterized in that: include: Generates proportional to absolute temperature PTAT current and complementary to absolute temperature CTAT current; Generate a high-order curvature compensation voltage based on the PTAT current and the CTAT current; amplifying the generated high-order curvature compensation voltage through an operational amplifier, and superimposing the amplified high-order curvature compensation voltage to a bandgap reference output stage to obtain a compensated bandgap reference output voltage; The bandgap reference output is calibrated for the compensated bandgap reference output voltage to ensure that the temperature drift coefficient of the output bandgap reference voltage is less than a preset threshold within a preset temperature range.

2. The method for compensating high-order curvature of a bandgap reference source based on an operational amplifier according to claim 1, wherein: Generates proportional-to-absolute-temperature (PTAT) current and complementary-to-absolute-temperature (CTAT) current, including: The PTAT current and CTAT current are generated respectively by a dual operational amplifier current-mode bandgap reference circuit.

3. The method for compensating high-order curvature of a bandgap reference source based on an operational amplifier according to claim 2, wherein: Assume that the parallel ratio of bipolar transistors in the dual operational amplifier current-mode bandgap reference circuit is 1: M ; The generated PTAT current and CTAT current The expressions are: in, is the thermal voltage of the bipolar transistor in the dual operational amplifier current-mode bandgap reference circuit; is the resistance value connected in series between the emitters of the two bipolar transistors, is the resistance value connected in parallel between the collector and emitter of the bipolar transistor; is the base-emitter voltage of the bipolar transistor.

4. The method for compensating high-order curvature of a bandgap reference source based on an operational amplifier according to claim 1, wherein: Based on the PTAT current and CTAT current, a high-order curvature compensation voltage is generated, including: The PTAT current and the CTAT current are copied and led out of the dual operational amplifier current mode bandgap reference circuit to a high-order curvature compensation circuit module by a cascode current mirror; wherein the high-order curvature compensation circuit module includes a first NPN bipolar transistor and a second bipolar transistor arranged in parallel, and the parallel ratio of the first bipolar transistor to the second bipolar transistor is set to 1: Q ; and the emitter of the second bipolar transistor is connected to the emitter of the first bipolar transistor through an N-channel field effect transistor; In the high-order curvature compensation circuit module, the PTAT current and the CTAT current are input into a first bipolar transistor and a second bipolar transistor connected in parallel in a certain ratio; then the required high-order curvature compensation voltage is generated at the drain of the N-channel field effect transistor.

5. The method for compensating high-order curvature of a bandgap reference source based on an operational amplifier according to claim 4, wherein: Inputting the PTAT current and the CTAT current into a first bipolar transistor and a second bipolar transistor connected in parallel according to a certain ratio, comprising: The first bipolar transistor inputs a PTAT current of a first preset input ratio; The second bipolar transistor simultaneously inputs the PTAT current and the CTAT current of a second preset input ratio.

6. The method for compensating high-order curvature of a bandgap reference source based on an operational amplifier according to claim 4, wherein: High-order curvature compensation voltage The expression is: in, is the base-emitter voltage of the first bipolar transistor; is the base-emitter voltage of the second bipolar transistor; T is the temperature of the circuit; is the Boltzmann constant; is the electron charge; is the preset reference temperature.

7. The method for compensating high-order curvature of a bandgap reference source based on an operational amplifier according to claim 1, wherein: Compensated bandgap reference output voltage The expression is: in, In series with the output reference voltage The base-emitter voltage of the bipolar transistor of the output stage; is the high-order curvature compensation voltage; is the amplification factor of the high-order curvature compensation voltage; is the output resistance of the bandgap reference voltage output circuit; is the PTAT current.

8. The method for compensating high-order curvature of a bandgap reference source based on an operational amplifier according to claim 5, wherein: The bandgap reference output is calibrated for the compensated bandgap reference output voltage to ensure that the temperature drift coefficient of the output bandgap reference voltage is less than a preset threshold within a preset temperature range, including: Draw a curve showing the variation of the compensated bandgap reference output voltage over the temperature range of -40 to 125 degrees Celsius. Based on the change curve, a bandgap reference voltage temperature drift coefficient is calculated; According to the bandgap reference voltage temperature drift coefficient, the input ratio of the PTAT current in the high-order curvature compensation circuit module is adjusted to ensure that the output bandgap reference voltage temperature drift coefficient is less than a preset threshold within a preset temperature range.

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