A high-precision, low-noise bandgap reference source without an op-amp structure

Abstract

The present invention relates to a high-precision, low-noise bandgap reference source without an op-amp structure, and belongs to the field of electronic circuits. The bandgap reference source comprises a startup circuit and a bandgap core circuit. The startup circuit is used to start the circuit when it is powered on, and has a multiple startup function; the bandgap core circuit is used to generate a reference voltage. The present invention improves the image precision of the circuit without an op-amp structure by adopting a common source and common gate current mirror in the bandgap core circuit module, and greatly reduces the overall low-frequency noise of the bandgap circuit by adopting a structure without an op-amp.

Description

Technical Field

[0001] The invention belongs to the field of electronic circuits and relates to a high-precision, low-noise bandgap reference source with no operational amplifier structure. Background Art

[0002] As a key module in analog and mixed analog circuits, bandgap reference circuits are widely used in DC / DC converters, AC / DC converters, linear regulators and other circuits. Its performance determines the performance and function realization of the entire analog circuit and even the chip. In some high-performance mixed circuits, the noise of the bandgap reference output becomes extremely important to the noise of the overall circuit. However, because the conventional bandgap reference circuit uses an op amp for clamping, its low-frequency noise is relatively high, which will have a greater impact in high-performance mixed circuits. Summary of the invention

[0003] In view of this, an object of the present invention is to provide a high-precision, low-noise bandgap reference source without an operational amplifier structure.

[0004] In order to achieve the above object, the present invention provides the following technical solutions:

[0005] A high-precision, low-noise bandgap reference source without an operational amplifier structure, comprising a startup circuit and a bandgap core circuit;

[0006] The startup circuit includes an eighth MOS tube M8, a ninth MOS tube M9, a tenth MOS tube M10, an eleventh MOS tube M11 and a twelfth MOS tube M12;

[0007] The gates of M8, M9 and M10 are interconnected and connected to the ground AGND, wherein the source of M8 is connected to the power supply voltage AVDD, and the drain of M8 is connected to the source of M9;

[0008] The drain of M9 is connected to the source of M10;

[0009] The drain of M10 is interconnected with the drain of M11 and the gate of M12;

[0010] The gate of M11 is connected to the voltage VREF, and the source of M11 is connected to the ground voltage AGND;

[0011] The drain of M12 is connected to the voltage VBN2, and the source of M12 is connected to the ground voltage AGND;

[0012] The bandgap core circuit includes a first MOS tube M1, a second MOS tube M2, a third MOS tube M3, a fourth MOS tube M4, a fifth MOS tube M5, a sixth MOS tube M6, a seventh MOS tube M7, a thirteenth MOS tube M13, a fourteenth MOS tube M14, a fifteenth MOS tube M15, a first triode Q1, a second triode Q2, a third triode Q3, a fourth triode Q4, a first resistor R1, a second resistor R2, a third resistor R3 and a fourth resistor R4;

[0013] The gate of M1, the source of M12 and the collector of Q4 are interconnected, the source of M1 is connected to the ground voltage AGND, and the drain of M1, the gate of M12 and the drain of M14 are interconnected;

[0014] The drain of M2 and the source of M3 are interconnected;

[0015] The gate and drain of M3 are interconnected;

[0016] The source of M4 is connected to the power supply voltage AVDD, the gate of M4 and the gate of M5 are interconnected with the drain of M6, and the drain of M4 is connected to the source of M6;

[0017] The source of M5 is connected to the power supply voltage AVDD, and the drain of M5 is connected to the source of M7;

[0018] The gate of M6, the gate of M7 and the drain of M3 are interconnected;

[0019] The drain of M7, the gate of M15 and the collector of Q3 are interconnected;

[0020] The drain of M15 is connected to the power supply voltage AVDD, and the source voltage of M15 is connected to the upper ends of R1 and R3;

[0021] The base of Q1 and the base of Q4 are connected to the lower end of R1, that is, the upper end of R2, the collector of Q1 is connected to the base of Q2, and the emitter of Q1 is connected to the ground potential AGND;

[0022] The collector of Q2 is connected to the lower end of R3 and the base of Q3, and the emitter of Q2 is connected to the ground potential AGND;

[0023] The emitter of Q3 is connected to the ground potential AGND.

[0024] Optionally, the first resistor R1 , the second resistor R2 , and the third resistor R3 are all polysilicon resistors with negative temperature coefficients.

[0025] Optionally, when the startup circuit is powered on, the gates of M8 to M10 are at a low level, and M8 to M10 are turned on. At this time, the circuit has not started yet, VREF is at a low level, M11 is not turned on, the gate of M12 is pulled high, M12 is turned on, the VBN2 voltage is pulled low, VBN2 in the bandgap core circuit is pulled low, and current is injected, the circuit begins to be established, and after the bandgap core circuit is established, VREF reaches the threshold voltage of M11 tube, and M11 tube is turned on, and then the gate voltage of M12 tube is pulled low, and M12 tube is turned off, and the startup circuit is closed at this time;

[0026] When the startup circuit is closed and the bandgap core works normally, Q1 and Q4 are current mirrors that mirror the current through Q1, and M4 to M7 are cascode current mirrors that mirror the current through Q4 to ensure that the current through Q3 is the same as the current through Q1, the base-emitter voltages of Q3 and Q1 are the same, and the voltages across R1 and R3 are the same, as shown in formula (1):

[0027] V R1 =V R3 = VREF-V BE1(3) (1)

[0028] VERF is the reference voltage; V BE1(3) is the base-emitter voltage of transistor Q3;

[0029] The current expression through transistor Q1 is shown in formula (2):

[0030]

[0031] V BE1 is the base-emitter voltage of transistor Q1;

[0032] V BE3 is the base-emitter voltage of transistor Q3;

[0033] K is the Boltzmann constant;

[0034] T is the thermodynamic temperature;

[0035] q is the electron charge;

[0036] A1 is the emitter area of ​​transistor Q1;

[0037] A2 is the emitter area of ​​transistor Q2;

[0038] The expression of VREF is shown in formula (3):

[0039]

[0040] The collector voltage of Q4 controlled by M1 and M2 is the same as the collector voltage of Q2. When the collector voltage of Q4 rises, the current through M1 rises, pulling down the gate voltage of M2, and then reducing the source voltage of M2, forming negative feedback and clamping the collector voltage of Q4 at the threshold voltage of M1.

[0041] The beneficial effects of the present invention are as follows: the present invention effectively improves the noise at low frequency by using triodes in the core circuit and utilizing the common source and common gate structure for the mirror current structure, and uses two current mirrors to mirror the current to improve the accuracy of the mirror without operational amplifier.

[0042] Other advantages, objectives and features of the present invention will be described in the following description to some extent, and to some extent, will be obvious to those skilled in the art based on the following examination and study, or can be taught from the practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be described in detail below in conjunction with the accompanying drawings, wherein:

[0044] Figure 1 The principle diagram of the high-precision, low-noise bandgap reference source without operational amplifier structure provided by the present invention;

[0045] Figure 2 The temperature characteristic curve of the high-precision, low-noise bandgap reference source without operational amplifier structure provided by the present invention;

[0046] Figure 3 The noise curve of the high-precision, low-noise bandgap reference source without operational amplifier structure provided by the present invention. DETAILED DESCRIPTION

[0047] The following describes the embodiments of the present invention by specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments only illustrate the basic concept of the present invention in a schematic manner, and the following embodiments and features in the embodiments can be combined with each other without conflict.

[0048] Among them, the drawings are only used for illustrative explanations, and they only represent schematic diagrams rather than actual pictures, and should not be understood as limitations on the present invention. In order to better illustrate the embodiments of the present invention, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of actual products. For those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.

[0049] The same or similar numbers in the drawings of the embodiments of the present invention correspond to the same or similar parts; in the description of the present invention, it should be understood that if the terms "upper", "lower", "left", "right", "front", "rear", etc. indicate the orientation or position relationship, they are based on the orientation or position relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, the terms describing the position relationship in the drawings are only used for illustrative purposes and cannot be understood as limiting the present invention. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0050] Figure 1 The present invention provides a schematic diagram of a high-precision, low-noise bandgap reference source without an operational amplifier structure, comprising a startup circuit and a bandgap reference core circuit.

[0051] Startup circuit such as Figure 1 As shown, when the power is just turned on, because the gates of M8~M10 are at a low level, M8~M10 are turned on. At this time, the circuit has not started yet, VREF is at a low level, M11 is not turned on, the gate of M12 is pulled high, and then M12 is turned on, the VBN2 voltage is pulled down, VBN2 in the bandgap core circuit is pulled down, and current is injected, the circuit begins to build, when the bandgap core circuit is built, VREF reaches the threshold voltage of M11 tube, M11 tube is turned on, and then the gate voltage of M12 tube is pulled down, M12 tube is turned off, and the startup circuit is closed at this time.

[0052] When the startup circuit is closed and the bandgap core works normally, Q1 and Q4 are current mirrors that mirror the current through Q1, and M4 to M7 are cascode current mirrors that mirror the current through Q4 to ensure that the current through Q3 is the same as the current through Q1. At this time, the base-emitter voltages of Q3 and Q1 are the same, and the voltages across R1 and R3 are the same, as shown in formula (1):

[0053] V R1 =V R3 = VREF-V BE1(3) (1)

[0054] The current expression through transistor Q1 is shown in formula (2):

[0055]

[0056] The final VREF expression is shown in formula (3):

[0057]

[0058] The collector voltage of Q4 controlled by M1 and M2 is the same as the collector voltage of Q2. When the collector voltage of Q4 rises, the current through M1 rises, pulling down the gate voltage of M2, and then reducing the source voltage of M2, forming negative feedback and clamping the collector voltage of Q4 near the threshold voltage of M1.

[0059] Figure 2 : is the temperature characteristic curve of the bandgap reference circuit provided by the present invention in the embodiment. It can be seen that the temperature coefficient of the bandgap reference circuit proposed by the present invention in the range of -40 to 125°C is 8.7ppm / °C.

[0060] Figure 3 : is the noise spectrum curve of the bandgap reference circuit provided by the present invention in the embodiment. It can be seen that the noise of the bandgap reference circuit provided by the present invention at the low frequency of 0.1Hz-10Hz is 2.27μV.

[0061] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution, which should be included in the scope of the claims of the present invention.

Claims

1. A high-precision, low-noise bandgap reference source without an operational amplifier structure, characterized in that: Including startup circuit and bandgap core circuit; The startup circuit includes an eighth MOS tube M8, a ninth MOS tube M9, a tenth MOS tube M10, an eleventh MOS tube M11 and a twelfth MOS tube M12; The gates of M8, M9 and M10 are interconnected and connected to the ground AGND, wherein the source of M8 is connected to the power supply voltage AVDD, and the drain of M8 is connected to the source of M9; The drain of M9 is connected to the source of M10; The drain of M10 is interconnected with the drain of M11 and the gate of M12; The gate of M11 is connected to the voltage VREF, and the source of M11 is connected to the ground voltage AGND; The drain of M12 is connected to the voltage VBN2, and the source of M12 is connected to the ground voltage AGND; The bandgap core circuit includes a first MOS tube M1, a second MOS tube M2, a third MOS tube M3, a fourth MOS tube M4, a fifth MOS tube M5, a sixth MOS tube M6, a seventh MOS tube M7, a thirteenth MOS tube M13, a fourteenth MOS tube M14, a fifteenth MOS tube M15, a first triode Q1, a second triode Q2, a third triode Q3, a fourth triode Q4, a first resistor R1, a second resistor R2, a third resistor R3 and a fourth resistor R4; The gate of M1, the source of M12 and the collector of Q4 are interconnected, the source of M1 is connected to the ground voltage AGND, and the drain of M1, the gate of M12 and the drain of M14 are interconnected; The drain of M2 and the source of M3 are interconnected; The gate and drain of M3 are interconnected; The source of M4 is connected to the power supply voltage AVDD, the gate of M4 and the gate of M5 are interconnected with the drain of M6, and the drain of M4 is connected to the source of M6; The source of M5 is connected to the power supply voltage AVDD, and the drain of M5 is connected to the source of M7; The gate of M6, the gate of M7 and the drain of M3 are interconnected; The drain of M7, the gate of M15 and the collector of Q3 are interconnected; The drain of M15 is connected to the power supply voltage AVDD, and the source voltage of M15 is connected to the upper ends of R1 and R3; The base of Q1 and the base of Q4 are connected to the lower end of R1, that is, the upper end of R2, the collector of Q1 is connected to the base of Q2, and the emitter of Q1 is connected to the ground potential AGND; The collector of Q2 is connected to the lower end of R3 and the base of Q3, and the emitter of Q2 is connected to the ground potential AGND; The emitter of Q3 is connected to the ground potential AGND.

2. A high-precision, low-noise bandgap reference source without an operational amplifier structure according to claim 1, characterized in that: The first resistor R1 , the second resistor R2 and the third resistor R3 are all polysilicon resistors with negative temperature coefficients.

3. A high-precision, low-noise bandgap reference source without an operational amplifier structure according to claim 1, characterized in that: When the startup circuit is powered on, the gates of M8 to M10 are at a low level, and M8 to M10 are turned on. At this time, the circuit has not started yet, VREF is at a low level, M11 is not turned on, the gate of M12 is pulled high, M12 is turned on, the VBN2 voltage is pulled low, VBN2 in the bandgap core circuit is pulled low, and current is injected, the circuit starts to be established, and when the bandgap core circuit is established, VREF reaches the threshold voltage of M11 tube, and M11 tube is turned on, and then the gate voltage of M12 tube is pulled low, and M12 tube is turned off, and the startup circuit is closed at this time; When the startup circuit is closed and the bandgap core works normally, Q1 and Q4 are current mirrors that mirror the current through Q1, and M4 to M7 are cascode current mirrors that mirror the current through Q4 to ensure that the current through Q3 is the same as the current through Q1, the base-emitter voltages of Q3 and Q1 are the same, and the voltages across R1 and R3 are the same, as shown in formula (1): V R1 =V R3 =VREF-V BE1(3) (1) VERF is the reference voltage; V BE1(3) is the base-emitter voltage of transistor Q3; The current expression through transistor Q1 is shown in formula (2): V BE1 is the base-emitter voltage of transistor Q1; V BE3 is the base-emitter voltage of transistor Q3; K is the Boltzmann constant; T is the thermodynamic temperature; q is the electron charge; A1 is the emitter area of ​​transistor Q1; A2 is the emitter area of ​​transistor Q2; The expression of VREF is shown in formula (3): The collector voltage of Q4 controlled by M1 and M2 is the same as the collector voltage of Q2. When the collector voltage of Q4 rises, the current through M1 rises, pulling down the gate voltage of M2, and then reducing the source voltage of M2, forming negative feedback and clamping the collector voltage of Q4 at the threshold voltage of M1.

Images