CN115373460B - Voltage reference source and integrated circuit - Google Patents
Voltage reference source and integrated circuit Download PDFInfo
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- CN115373460B CN115373460B CN202211128436.XA CN202211128436A CN115373460B CN 115373460 B CN115373460 B CN 115373460B CN 202211128436 A CN202211128436 A CN 202211128436A CN 115373460 B CN115373460 B CN 115373460B
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- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05F—SYSTEMS FOR REGULATING ELECTRIC OR MAGNETIC VARIABLES
- G05F1/00—Automatic systems in which deviations of an electric quantity from one or more predetermined values are detected at the output of the system and fed back to a device within the system to restore the detected quantity to its predetermined value or values, i.e. retroactive systems
- G05F1/10—Regulating voltage or current
- G05F1/46—Regulating voltage or current wherein the variable actually regulated by the final control device is DC
- G05F1/56—Regulating voltage or current wherein the variable actually regulated by the final control device is DC using semiconductor devices in series with the load as final control devices
- G05F1/565—Regulating voltage or current wherein the variable actually regulated by the final control device is DC using semiconductor devices in series with the load as final control devices sensing a condition of the system or its load in addition to means responsive to deviations in the output of the system, e.g. current, voltage, power factor
- G05F1/567—Regulating voltage or current wherein the variable actually regulated by the final control device is DC using semiconductor devices in series with the load as final control devices sensing a condition of the system or its load in addition to means responsive to deviations in the output of the system, e.g. current, voltage, power factor for temperature compensation
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Abstract
The invention discloses a variety of voltage reference sources and an integrated circuit, and relates to the technical field of integrated circuits, wherein a first output end of an adjustable current generation module is connected with a delta VGS generation module, and a second output end of the adjustable current generation module is connected with an output module; the delta VGS generating module is connected with the first transistor, and the output end of the delta VGS generating module is connected with the output module; the transistor and the first transistor in the delta VGS generation module work in a subthreshold region, the delta VGS generation module is used for outputting delta VGS voltage, and the adjustable current generation module is used for adjusting the delta VGS voltage to be a value that the threshold voltage of the first transistor extends to absolute zero degree so as to output reference voltage. When the value of ΔVGS voltage is equal to the value of the threshold voltage of the first transistor extending to absolute zero, the output reference voltage is made constant with temperature under given process conditions and device size, and the current flowing to the output module is made to be the reference current with uT 2 characteristics.
Description
Technical Field
The present invention relates to the field of integrated circuits, and in particular, to a voltage reference source and an integrated circuit.
Background
The conventional bandgap voltage reference source can provide a reference voltage having an extremely low temperature coefficient so as to be widely used in various integrated circuit products, but has the disadvantages of higher power consumption and larger area due to the structural characteristics of the bandgap reference source. In the application occasions of a non-battery power supply system or battery power supply based on energy collection, which need to meet the requirement of ultra-long standby time, the reference source needs to have the performance of nano-watt and even picowatt power consumption, and the product is sensitive to the chip area cost due to the characteristic of large-scale deployment, and the band gap reference source is generally in the micro-watt level and has larger area, so the band gap reference source is not suitable for the application.
The nanowatt power consumption voltage reference source is usually realized based on the fact that the threshold voltage of the MOS transistor extends to a value VTH0 of absolute zero, most of MOS transistors in the circuit work under the subthreshold condition so as to achieve the purpose of extremely low power consumption, and the circuit is realized without a passive resistor, so that the purpose of reducing the area of a chip and lowering the cost is achieved. Common implementation manners of the circuit include a double-tube structure, a three-tube structure, a circuit structure based on the zero temperature drift operating point characteristic of the MOS transistor, a voltage source structure based on the characteristic reference current of the uT 2 and the like. Wherein, the double-tube structure and the three-tube structure have high sensitivity to the process and difficult control of the temperature coefficient despite extremely low power consumption and simple structure. The current research on a circuit structure based on the zero temperature drift operating point characteristic of the MOS transistor is insufficient.
The most fully studied nanowatt power consumption reference source based on MOS transistor threshold voltage is mainly composed of two parts, the first part generates a characteristic reference current with uT 2, and the second part generates a low temperature coefficient voltage reference based on threshold voltage by means of VGS and Δvgs combination. In a typical threshold voltage based CMOS nanowatt power consumption voltage reference source structure, a characteristic reference current generating circuit with uT 2 is usually composed of four core transistors plus a current mirror, and VGS and Δvgs are combined to generate a threshold voltage based low temperature coefficient voltage reference consisting of at least three transistors. Therefore, without the inclusion of an auxiliary circuit such as a current mirror, a nanowatt power consumption reference source with a typical structure based on the threshold voltage of a MOS transistor is composed of at least seven transistors, and the voltage reference thus generated generally does not have the capability of driving a resistive load, requiring an additional driving buffer circuit.
Therefore, how to reduce the number of transistors in the voltage reference source, providing a reference source with a simple structure is an urgent problem to be solved by those skilled in the art.
Disclosure of Invention
The invention aims to provide a voltage reference source, which can generate low-temperature coefficient reference voltage and reference current with uT 2 characteristics only by arranging a small number of transistors; another object of the present invention is to provide an integrated circuit that requires only a small number of transistors to generate a low temperature coefficient reference voltage and a reference current with the characteristics of uT 2.
In order to solve the technical problems, the invention provides a voltage reference source, which comprises a first transistor, a delta VGS generating module, an adjustable current generating module and an output module;
The adjustable current generation module comprises at least a first output end and a second output end, wherein the first output end is connected with the delta VGS generation module, and the second output end is connected with the output module; the delta VGS generation module is connected with the first transistor, and the output end of the delta VGS generation module is connected with the output module;
The transistor and the first transistor in the delta VGS generation module work in a subthreshold region, the delta VGS generation module is used for outputting delta VGS voltage, and the adjustable current generation module is used for adjusting the delta VGS voltage to be a value of which the threshold voltage of the first transistor extends to an absolute zero degree so as to output reference voltage.
Optionally, the output module includes an output transistor, a gate of the output transistor is connected to an output end of the Δvgs generating module, a drain of the output transistor is connected to the second output end, and the output transistor works in a saturation region.
Optionally, the threshold voltage of the first transistor is equal to the threshold voltage of the output transistor, and the output end of the Δvgs generating module is directly connected to the gate of the output transistor.
Optionally, the output end of the Δvgs generating module is connected with the buffer, the buffer is connected with the gate of the output transistor, and the buffer is used for compensating errors generated by differences between the threshold voltage of the first transistor and the threshold voltage of the output transistor.
Optionally, the buffer is a linear buffer.
Optionally, the linear buffer includes an operational amplifier, and a feedback network connected to the operational amplifier, and an output end of the Δvgs generating module is connected to the operational amplifier.
Optionally, the adjustable current generating module includes a current mirror, and the current mirror includes a first output terminal transistor connected to the first output terminal, and a second output terminal transistor connected to the second output terminal.
Optionally, the Δvgs generating module includes a Δvgs generating unit, the Δvgs generating unit includes a second transistor and a third transistor, a drain of the second transistor is connected to a source of the third transistor, a drain of the third transistor is connected to the first output terminal, and a gate of the second transistor and a gate of the third transistor are both connected to the first output terminal.
Optionally, the Δvgs generating module includes a plurality of Δvgs generating units, and the plurality of Δvgs generating units are connected in series with each other; the current mirror comprises first output end transistors which are in one-to-one correspondence with the delta VGS generation units, and the first output end transistors are connected with the corresponding delta VGS generation units.
The invention also provides an integrated circuit comprising a voltage reference source as claimed in any one of the preceding claims.
The invention provides a voltage reference source, which comprises a first transistor, a delta VGS generation module, an adjustable current generation module and an output module, wherein the first transistor is connected with the delta VGS generation module; the adjustable current generation module comprises at least a first output end and a second output end, wherein the first output end is connected with the delta VGS generation module, and the second output end is connected with the output module; the delta VGS generating module is connected with the first transistor, and the output end of the delta VGS generating module is connected with the output module; the transistor and the first transistor in the delta VGS generation module work in a subthreshold region, the delta VGS generation module is used for outputting delta VGS voltage, and the adjustable current generation module is used for adjusting the delta VGS voltage to be a value of the threshold voltage of the first transistor extending to absolute zero degree so as to output reference voltage.
The specific value of the ΔVGS voltage can be regulated by the adjustable current generation module, when the value of the ΔVGS voltage is equal to the value of the threshold voltage of the first transistor, the output reference voltage is made to be constant which is not changed with temperature under given process conditions and device size, and meanwhile, the current flowing to the output module is made to be the reference current with uT 2 characteristics. By embedding the circuit structure of the combination VGS and Δvgs into the characteristic reference current circuit structure with uT 2, a reference voltage with a low temperature coefficient is obtained by adjusting the proportionality coefficient of the current. Besides the auxiliary circuit, the full functions of the two can be realized by only four transistors at least, and the number of the transistors is greatly reduced.
The invention also provides an integrated circuit which has the same beneficial effects and is not described in detail herein.
Drawings
For a clearer description of embodiments of the invention or of the prior art, the drawings that are used in the description of the embodiments or of the prior art will be briefly described, it being apparent that the drawings in the description below are only some embodiments of the invention, and that other drawings can be obtained from them without inventive effort for a person skilled in the art.
FIG. 1 is a schematic diagram of a voltage reference source according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of a specific voltage reference source according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of another embodiment of a voltage reference source according to the present invention;
Fig. 4 is a graph of voltage reference source output voltage V REF as a function of temperature.
In the figure: the circuit comprises a delta VGS generation module 1, a delta VGS generation unit 11, an adjustable current generation module 2, an output module 3, a buffer 4, a first transistor M1, a second transistor M2/M21/M22 … M2N, a third transistor M3/M31/M32 … M3N, an output transistor M4, a first output end transistor M5/M51/M52 … M5N, a second output end transistor M6, an operational amplifier A1 and a feedback network beta 1.
Detailed Description
The core of the invention is to provide a voltage reference source. In the prior art, the characteristic reference current generation circuit with uT 2 is typically composed of four core transistors plus current mirrors, and VGS and Δvgs combined to generate a low temperature coefficient voltage reference based on the threshold voltage is composed of at least three transistors. Therefore, without taking into account auxiliary circuits such as current mirrors, a reference source for nanowatt power consumption, which is typically structured based on the threshold voltage of MOS transistors, is composed of at least seven transistors.
The voltage reference source provided by the invention comprises a first transistor, a delta VGS generation module, an adjustable current generation module and an output module; the adjustable current generation module comprises at least a first output end and a second output end, wherein the first output end is connected with the delta VGS generation module, and the second output end is connected with the output module; the delta VGS generating module is connected with the first transistor, and the output end of the delta VGS generating module is connected with the output module; the transistor and the first transistor in the delta VGS generation module work in a subthreshold region, the delta VGS generation module is used for outputting delta VGS voltage, and the adjustable current generation module is used for adjusting the delta VGS voltage to be a value that the threshold voltage of the first transistor extends to absolute zero degree so as to output reference voltage.
The specific value of the delta VGS voltage can be regulated by the adjustable current generation module, when the value of the delta VGS voltage is equal to the value of the threshold voltage of the first transistor, the output reference voltage is constant which is not changed with temperature under given process conditions and device size, and meanwhile, the current flowing to the output module is the reference current with the uT 2 characteristic. By embedding the circuit structure of the combination VGS and Δvgs into the characteristic reference current circuit structure with uT 2, a reference voltage with a low temperature coefficient is obtained by adjusting the proportionality coefficient of the current. Besides the auxiliary circuit, the full functions of the two can be realized by only four transistors at least, and the number of the transistors is greatly reduced.
In order to better understand the aspects of the present invention, the present invention will be described in further detail with reference to the accompanying drawings and detailed description. It will be apparent that the described embodiments are only some, but not all, embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Referring to fig. 1, fig. 1 is a schematic structural diagram of a voltage reference source according to an embodiment of the invention.
Referring to fig. 1, in an embodiment of the present invention, the voltage reference source includes a first transistor M1, a Δvgs generating module 1, an adjustable current generating module 2, and an output module 3; the adjustable current generation module 2 comprises at least a first output end and a second output end, wherein the first output end is connected with the delta VGS generation module 1, and the second output end is connected with the output module 3; the Δvgs generating module 1 is connected with the first transistor M1, and the output end of the Δvgs generating module 1 is connected with the output module 3; the transistors in the Δvgs generating module 1 and the first transistor M1 are both operated in a subthreshold region, the Δvgs generating module 1 is configured to output a Δvgs voltage, and the adjustable current generating module 2 is configured to adjust the Δvgs voltage to a value that the threshold voltage of the first transistor M1 extends to an absolute zero degree so as to output a reference voltage.
The first transistor M1 is used for generating the gate-source voltage VGS, one end of the first transistor M1 is usually grounded, the other end needs to be connected to the Δvgs generation module 1, and the Δvgs generation module 1 is used for generating the Δvgs voltage. The Δvgs voltage is a voltage obtained by subtracting the gate-source voltages VGS of the two transistors, and is referred to as Δvgs voltage. Therefore, the Δvgs generating module 1 includes at least two transistors to generate two gate-source voltages VGS and to make a difference to obtain a Δvgs voltage. The first transistor M1 is combined with the Δvgs generating module 1 to generate an output Δvgs voltage, and then the Δvgs voltage is adjusted by the adjustable current generating module 2 to obtain a reference voltage with a low temperature coefficient.
The adjustable current generating module 2 includes at least a first output terminal and a second output terminal, wherein the first output terminal is connected to the Δvgs generating module 1, the second output terminal is connected to the output module 3, and the output terminal of the Δvgs generating module 1 is also connected to the output module 3. The adjustable current generating module 2 may be a current mirror or any other structure, and the adjustable current generating module 2 is configured to generate a current with an adjustable proportion, and can specifically adjust the proportion of the current flowing between the first output end and the second output end, so as to adjust the output voltage of the Δvgs generating module 1.
The output module 3 generally has three ends, one end is connected to the second output terminal of the adjustable current generating module 2, one end is connected to the output terminal of the Δvgs generating module 1, and the last end is grounded.
In the actual operation process, the transistors in the first transistor M1 and the Δvgs generating module 1 operate in the subthreshold region, and the transistors are in the subthreshold state at this time. The specific content of the Guan Ya threshold region can be referred to in the prior art, and will not be described in detail herein.
Specifically, in the embodiment of the present invention, the output module 3 includes an output transistor M4, a gate of the output transistor M4 is connected to the output end of the Δvgs generating module 1, a drain of the output transistor M4 is connected to the second output end, and the output transistor M4 operates in a saturation region.
The output module 3 may be a transistor, namely the output transistor M4, the gate of the output transistor M4 needs to be connected to the output terminal of the Δvgs generating module 1, the drain of the output transistor M4 needs to be connected to the second output terminal of the adjustable current generating module 2, and the source of the output transistor M4 needs to be grounded. When the output transistor M4 works in a saturation region, the emission junction of the output transistor M4 is forward biased, the collection junction is also forward biased, and the collector current is not controlled by the base current. When the Δvgs voltage is equal to the value of the threshold voltage of the first transistor M1 extending to absolute zero, the reference voltage outputted by the voltage reference source provided by the embodiment of the present invention is equal to the value of the threshold voltage of the output transistor M4 extending to absolute zero, and the reference voltage has an extremely low temperature coefficient.
Specifically, the adjustable current generating module 2 includes a current mirror, where the current mirror includes a first output terminal transistor M5 connected to the first output terminal, and a second output terminal transistor M6 connected to the second output terminal.
That is, in the embodiment of the present invention, a current mirror is used as the adjustable current generating module 2, and the control of the output current ratio between the first output terminal and the second output terminal is realized through the current mirror, so that the magnitude of the Δvgs voltage output by the Δvgs generating module 1 can be controlled. The current mirror comprises a first output end transistor M5 and a second output end transistor M6, wherein the first output end transistor M5 is connected with the first output end and is connected with the delta VGS generation module 1; the second output terminal transistor M6 is connected to the second output terminal and to the output module 3. Specifically, the gate of the first output transistor M5 is connected to the gate of the second output transistor M6, the drain of the first output transistor M5 needs to be connected to the Δvgs generating module 1, and the drain of the second output transistor M6 needs to be connected to the output module 3.
Specifically, the Δvgs generating module 1 includes a Δvgs generating unit 11, where the Δvgs generating unit 11 includes a second transistor M2 and a third transistor M3, a drain of the second transistor M2 is connected to a source of the third transistor M3, a drain of the third transistor M3 is connected to the first output terminal, and a gate of the second transistor M2 and a gate of the third transistor M3 are connected to the first output terminal.
The drain of the second transistor M2 needs to be connected to the source of the third transistor M3, and the gate of the second transistor M2, the gate of the third transistor M3, and the drain of the third transistor M3 need to be connected to the first output terminal of the adjustable current generating module 2. The first transistor M1 is connected to the second transistor M2 by diode connection, i.e. the drain and gate of the first transistor M1 are connected to the source of the second transistor M2. At this time, the junction of the drain of the second transistor M2 and the source of the third transistor M3 may output the Δvgs voltage.
It should be noted that, because degenerate working points exist in the circuit structure of the voltage reference source, in the specific implementation, a starting circuit is also required to be added in the circuit provided by the embodiment of the present invention, and the specific content of the starting circuit can refer to the prior art, and no detailed description is given here.
In the embodiment of the present invention, the Δvgs voltage outputted by the Δvgs generating module 1 needs to be adjusted to be equal to the value of the threshold voltage of the first transistor M1 extending to absolute zero by the adjustable current generating module 2, and the finally outputted reference voltage is equal to the value of the threshold voltage of the output transistor M4 extending to absolute zero. Therefore, in the embodiment of the present invention, a buffer structure may be additionally disposed between the output end of the Δvgs generating module 1 and the output module 3, and the specific content thereof will be described in detail in the following embodiment of the present invention. In the embodiment of the present invention, the threshold voltage of the first transistor M1 may be specifically set to be equal to the threshold voltage of the output transistor M4, and the buffer structure may be omitted at this time, so that the output terminal of the Δvgs generating module 1 is directly connected to the gate of the output transistor M4.
In the embodiment of the invention, the output reference voltage acts on the output transistor M4 to generate the pull-down current. The pull-down current can be mirrored to the first output end transistor M5 through the second output end transistor M6 to supply power, so that the dependence of the adjustable current generation module 2 on an external power supply is reduced, and the interference of the external current on the voltage reference source provided by the embodiment of the invention is reduced.
According to the voltage reference source provided by the embodiment of the invention, the specific value of the delta VGS voltage can be regulated through the adjustable current generation module 2, when the value of the delta VGS voltage is equal to the value of the threshold voltage of the first transistor M1 and extends to the absolute zero degree, the output reference voltage is a constant which does not change along with the temperature under given process conditions and device size, and meanwhile, the current flowing to the output module 3 is the reference current with the uT 2 characteristic. By embedding the circuit structure of the combination VGS and Δvgs into the characteristic reference current circuit structure with uT 2, a reference voltage with a low temperature coefficient is obtained by adjusting the proportionality coefficient of the current. Besides the auxiliary circuit, the full functions of the two can be realized by only four transistors at least, and the number of the transistors is greatly reduced.
The specific structure of a voltage reference source provided by the present invention will be described in detail in the following embodiments of the invention.
Referring to fig. 2, fig. 2 is a schematic structural diagram of a specific voltage reference source according to an embodiment of the invention.
The embodiment of the present invention is different from the embodiment of the present invention, and the structure of the voltage reference source is further defined based on the embodiment of the present invention, and the rest of the content is described in detail in the embodiment of the present invention, which is not described herein.
Referring to fig. 2, in the embodiment of the present invention, the Δvgs generating module 1 includes a plurality of Δvgs generating units 11, and the plurality of Δvgs generating units 11 are connected in series with each other; the current mirror includes first output end transistors M5 in one-to-one correspondence with the Δvgs generating units 11, and the first output end transistors M5 are connected with the corresponding Δvgs generating units 11.
That is, in the embodiment of the present invention, a plurality of Δvgs generating units 11 may be provided in total, and the plurality of Δvgs generating units 11 need to be connected in series with each other. At this time, the above-mentioned Δvgs generating units 11 are connected in series with each other means that the output terminal of the previous Δvgs generating unit 11 in the current direction is connected to the end of the next Δvgs generating unit 11 which is originally required to be connected to the first transistor M1, that is, the output terminal of the previous Δvgs generating unit 11 in the current direction is required to be connected to the source of the second transistor M2 in the next Δvgs generating unit 11, so that a series structure is formed. In this tandem configuration, the Δvgs generating unit 11 at the head needs to be connected to the first transistor M1, and the Δvgs generating unit 11 at the tail needs to be connected to the output module 3.
Correspondingly, a plurality of first output end transistors M5 are disposed in the current mirror to form a plurality of first output ends, and the first output end transistors M5 and the Δvgs generating unit 11 need to be in one-to-one correspondence. The first output transistors M5 need to be connected to the corresponding Δvgs generating units 11, and specifically, the drains of the first output transistors M5 need to be connected to the drains of the third transistors M3 in the corresponding Δvgs generating units 11 in a current mirror provided with a plurality of first output transistors M5, and the gates of each first output transistor M5 need to be connected to the second output transistor M6, so as to form a total of N current ratio parameters from K1 to KN.
In the embodiment of the invention, the plurality of delta VGS generating units 11 are arranged to conveniently adjust the temperature coefficient, and different current sizes are adjusted according to actual needs, so that the voltage reference source is adapted to various temperature coefficients and can work under various working conditions.
The specific structure of a voltage reference source provided by the present invention will be described in detail in the following embodiments of the invention.
Referring to fig. 3 and fig. 4, fig. 3 is a schematic structural diagram of another specific voltage reference source according to an embodiment of the present invention; fig. 4 is a graph of voltage reference source output voltage V REF as a function of temperature.
The embodiment of the present invention is different from the embodiment of the present invention, and the structure of the voltage reference source is further defined based on the embodiment of the present invention, and the rest of the content is described in detail in the embodiment of the present invention, which is not described herein.
Referring to fig. 3, in the embodiment of the present invention, the voltage reference source further includes a buffer 4, the output terminal of the Δvgs generating module 1 is connected to the buffer 4, the buffer 4 is connected to the gate of the output transistor M4, and the buffer 4 is used for compensating an error generated by a difference between the threshold voltage of the first transistor M1 and the threshold voltage of the output transistor M4.
When the threshold voltage of the first transistor M1 is different from the threshold voltage of the output transistor M4, a buffer 4 needs to be disposed between the Δvgs generating module 1 and the output module 3, i.e. the output terminal of the Δvgs generating module 1 is connected to the buffer 4, and the buffer 4 is connected to the gate of the output transistor M4. The buffer 4 can compensate for errors due to the difference in threshold voltage between the first transistor M1 and the output transistor M4 on the one hand, and can provide the reference voltage V REF as the output buffer 4 on the other hand, which is capable of driving a resistive load.
Specifically, in the embodiment of the present invention, the buffer 4 is specifically a linear buffer 4, and the linear buffer 4 may specifically include an operational amplifier A1 and a feedback network β1 connected to the operational amplifier A1, where an output end of the Δvgs generating module 1 is connected to the operational amplifier A1, and an output end of the operational amplifier A1 is used to connect to the output module 3.
The principle of implementation of the voltage reference source will be described below taking fig. 3 as an example.
The first transistor M1 is a diode-connected MOS transistor, the gate-source voltage thereof is VGS1, the drain of the first transistor M1 is connected to the source of the second transistor M21, the second transistor M21 is connected to the source of the third transistor M31 to form a Δvgs circuit structure, so that the drain-source voltage of the second transistor M21 is the difference between the gate-source voltages VGS of the second transistor M21 and the third transistor M31, the difference is defined as Δvgs1, the N Δvgs circuit structures are connected in series as shown in fig. 3, the voltage obtained at the output end of the N Δvgs circuit series is V0, the operational amplifier A1 and the feedback network β1 form a linear buffer 4 with a feedback coefficient β1, which functions on the one hand to compensate for errors generated due to the difference between the threshold voltages of the first transistor M1 and the output transistor M4, and on the other hand can provide a resistive load driving capability of the reference voltage V REF as the output buffer 4. V0 gets the reference voltage V REF through the linear buffer A1/β1:
V0＝VGS1+AVGS1+ΔVGS2+…+ΔVGSN
VREFV0/β1
At this time, the reference voltage V REF is applied to the gate of the output transistor M4 to generate the current Id4, and the output transistor M4 is designed to operate in the saturation region in the embodiment of the present invention, the expression of the current is approximately:
The second output transistor M6, the first output transistors M51, M52 to M5N constitute a current mirror, and the ratio between the width-to-length ratio of the first output transistors M51, M52 to M5N and the width-to-length ratio of the second output transistor M6 is K1, K2 to KN, respectively. The first transistor M1, the second transistors M21 to 2N, and the third transistors M31 to M3N all suggest operating in the subthreshold region, and the drain current-voltage relationship of the first transistor M1 is:
Id1＝Id4(K1+K2+…+KN)
In the above formula T is absolute temperature, k is the boltzmann constant, q is the electron charge, mu n is the electron mobility, C ox is the capacitance per unit area of the gate oxide, and n is the subthreshold gradient factor. If V REF is a temperature independent reference voltage and its value happens to be equal to the value VTH4 of the output transistor M4, which extends to an absolute zero VTH2_0, I d4＝KμnT2 is known from the above equation, where K is a constant temperature independent coefficient and the currents of the other branches are proportional to I d4. The circuit is thus capable of generating a current having the uT 2 output characteristics. To be full V REF is a temperature independent reference voltage and its value exactly equal to the condition that the threshold voltage VTH4 of the output transistor M4 is spread to an absolute zero value VTH40, according to the above formula, and I d4＝KμnT2, it is possible to obtain:
V0＝VTH1+αVT
Where VTH1 has a negative temperature coefficient, α is a positive temperature coefficient, the value of which is determined primarily by the current mirror ratio coefficient and the transistor size ratio, it is possible to adjust these parameters such that V0 is equal to VTH1—0, i.e. the threshold voltage of the first transistor M1 is extended to a value of absolute zero. As long as the feedback coefficient β1 of the linear buffer 4 is adjusted such that:
VTH4_0＝VTH1_0/β1
When the above conditions are satisfied, I d4＝KμnT2 is obtained, and V0 is equal to VTH1_0 and V REF is equal to VTH4_0, where VTH1_0 and VTH4_0 are values when the threshold voltages of the first transistor M1 and the output transistor M4 are respectively extended to absolute zero degrees, and are constants that do not vary with temperature under given process conditions and device dimensions. Therefore, the circuit can simultaneously generate the current with uT 2 characteristics and the reference voltage with low temperature coefficient, and the circuit only uses the transistor and mainly works in the subthreshold region, so that the circuit has the advantages of extremely low power consumption and small area, and simultaneously provides an embedded reference voltage linear buffer driving function. The linear voltage buffer 4 may be omitted if the threshold voltages of the first transistor M1 and the output transistor M4 are equal and the reference voltage does not require an additional driving capability, as shown in fig. 2. Because the circuit has degenerate working points, when the circuit is implemented, a starting circuit is added in the circuit, and the structure of the starting circuit is determined according to the specific situation.
Compared with fig. 3, in the present application, the first transistor M1 and the output transistor M4 in fig. 3 are designed as transistors with equal threshold voltages, the linear buffer 4 formed by the operational amplifier A1 and the feedback network β1 in fig. 3 is eliminated, and N in the N series Δvgs circuit structures in fig. 3 takes a value of 1, that is, only one Δvgs circuit structure is used. Trimming of the output voltage is accomplished by adjusting the ratio K between the first output terminal transistor M5 and the second output terminal transistor M6. Since the circuit has degeneracy, the actual circuit requires a start-up circuit to operate, the contents of which are as the case may be, and is therefore represented in fig. 1 only in schematic block form. The theoretical value of the output reference voltage V REF is a value when the threshold voltage of the output transistor M4 is extended to absolute zero, and in this embodiment, a typical 65nm CMOS process is adopted, and a curve of the reference voltage changing with temperature is obtained through simulation, as shown in fig. 4, the reference voltage value is 596mV, the voltage temperature coefficient between forty degrees celsius and one hundred twenty-five degrees celsius is 13ppm, and the total current is about 200nA. The core structure of the circuit only comprises four transistors, namely a first transistor M1, a second transistor M2, a third transistor M3 and an output transistor M4, so that two functions of a uT 2 current source and a low-temperature drift voltage source are realized. The current source structure provided by the application can be realized by NMOS or PMOS, and only the NMOS transistor and the PMOS transistor in the figure are required to be exchanged and inverted.
The invention also provides an integrated circuit comprising a voltage reference source as provided in any one of the above embodiments of the invention. Reference may be made to the prior art for the remaining structure of the integrated circuit, and no further description is given here.
The voltage reference source provided by the embodiment of the invention can generate low-temperature coefficient reference voltage and reference current with uT 2 characteristic only through a small number of transistors, and the corresponding integrated circuit can have smaller area, thereby being beneficial to miniaturization of the integrated circuit.
In this specification, each embodiment is described in a progressive manner, and each embodiment is mainly described in a different point from other embodiments, so that the same or similar parts between the embodiments are referred to each other.
Those of skill would further appreciate that the various illustrative elements and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware, computer software, or combinations of both, and that the various illustrative elements and steps are described above generally in terms of functionality in order to clearly illustrate the interchangeability of hardware and software. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the solution. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention.
The steps of a method or algorithm described in connection with the embodiments disclosed herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. The software modules may be disposed in Random Access Memory (RAM), memory, read Only Memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art.
Finally, it is further noted that relational terms such as first and second, and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises the element.
The voltage reference source and the integrated circuit provided by the invention are described in detail above. The principles and embodiments of the present invention have been described herein with reference to specific examples, the description of which is intended only to facilitate an understanding of the method of the present invention and its core ideas. It should be noted that it will be apparent to those skilled in the art that various modifications and adaptations of the invention can be made without departing from the principles of the invention and these modifications and adaptations are intended to be within the scope of the invention as defined in the following claims.
Claims (8)
1. The voltage reference source is characterized by comprising a first transistor, a delta VGS generation module, an adjustable current generation module and an output module;
The adjustable current generation module comprises at least a first output end and a second output end, wherein the first output end is connected with the delta VGS generation module, and the second output end is connected with the output module; the delta VGS generation module is connected with the first transistor, and the output end of the delta VGS generation module is connected with the output module;
The transistor and the first transistor in the delta VGS generation module work in a subthreshold region, the delta VGS generation module is used for outputting delta VGS voltage, and the adjustable current generation module is used for adjusting the delta VGS voltage to be a value of absolute zero degree of the threshold voltage of the first transistor so as to output reference voltage;
The output module comprises an output transistor, the grid electrode of the output transistor is connected with the output end of the delta VGS generation module, the drain electrode of the output transistor is connected with the second output end, and the output transistor works in a saturation region;
the threshold voltage of the first transistor is equal to that of the output transistor, and the output end of the delta VGS generation module is directly connected with the grid electrode of the output transistor.
2. The voltage reference source of claim 1, further comprising a buffer, the output of the Δvgs generating module being connected to the buffer, the buffer being connected to the gate of the output transistor, the buffer being configured to compensate for errors caused by differences between the threshold voltage of the first transistor and the threshold voltage of the output transistor.
3. The voltage reference source of claim 2, wherein the buffer is a linear buffer.
4. A voltage reference source according to claim 3, wherein the linear buffer comprises an operational amplifier and a feedback network connected to the operational amplifier, the output of the Δvgs generating module being connected to the operational amplifier.
5. The voltage reference source of claim 1, wherein the adjustable current generation module comprises a current mirror comprising a first output transistor connected to the first output and a second output transistor connected to the second output.
6. The voltage reference source of claim 5, wherein the Δvgs generation module comprises a Δvgs generation unit comprising a second transistor and a third transistor, a drain of the second transistor being connected to a source of the third transistor, a drain of the third transistor being connected to the first output, a gate of the second transistor and a gate of the third transistor both being connected to the first output.
7. The voltage reference source of claim 6, wherein the Δvgs generating module comprises a plurality of Δvgs generating units, the plurality of Δvgs generating units being connected in series with one another; the current mirror comprises first output end transistors which are in one-to-one correspondence with the delta VGS generation units, and the first output end transistors are connected with the corresponding delta VGS generation units.
8. An integrated circuit comprising a voltage reference source as claimed in any one of claims 1 to 7.
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