Novel band-gap reference voltage source

Abstract

A novel band-gap reference voltage source comprises a first PNP tube and a second PNP tube, base electrodes and collector electrodes of the two PNP tubes are grounded, and emitter electrodes of the two PNP tubes are connected with a negative feedback circuit; the negative feedback circuit comprises a first P tube and a second P tube, source electrodes of the first P tube and the second P tube are connected with a power supply, grid electrodes of the first P tube and the second P tube are connected and connected with a drain electrode of the second P tube, and width-length ratios of the first P tube and the second P tube are equal; the emitter areas of the first PNP transistor and the second PNP transistor are different; the negative feedback circuit is further connected with a starting circuit and a voltage and current output circuit, and the starting circuit is used for providing starting current for the triode. According to the novel band-gap reference voltage source, an operational amplifier for clamping is not needed in a circuit, reference voltage which is not influenced by temperature can be obtained, errors caused by the operational amplifier are completely eradicated, and the voltage value of the output reference voltage can be adjusted.

Description

Technical Field

[0001] The invention belongs to the technical field of analog circuits, relates to a reference voltage circuit, and in particular to a novel bandgap reference voltage source. Background Art

[0002] A reference voltage source is a module that provides reference voltage and reference current to a circuit or chip. Almost all chips in an integrated circuit use a reference source circuit. It is widely used in oscillators, amplifiers, phase-locked loops and other modules. It is a key unit of an integrated circuit. The accuracy of the reference voltage source is crucial to the performance of the circuit.

[0003] In the past, the traditional voltage source was generally a bandgap reference voltage source, which was implemented using a bipolar transistor, and the output voltage was constant at about 1.25V; the working principle was to cancel each other out through the negative temperature coefficient VBE and the positive temperature coefficient ΔVBE, thereby obtaining a zero temperature coefficient voltage. However, this type of bandgap voltage source has the following problems in the COMS process:

[0004] like Figure 2 The figure shows a typical traditional bandgap reference voltage source circuit. In the traditional bandgap reference source, an operational amplifier AMP is often required to clamp the voltage of the two branches where the transistor is located, so as to generate a ΔVBE voltage with a positive temperature coefficient. However, the introduction of an operational amplifier will make the circuit structure more complicated, so that the circuit has two loops of positive feedback and negative feedback at the same time in a small range, and the circuit stability will be at risk. In addition, the offset voltage DC gain of the operational amplifier has a greater impact on the circuit performance, and the accuracy is not high.

[0005] Due to the physical parameters of the transistor, the output reference voltage is basically around 1.25V. If the system power supply voltage is less than 1.25V, Figure 2 The circuit structure shown cannot be used. If the system requires a reference voltage below 1.25V, the circuit structure cannot be used either, and the application is limited. Summary of the invention

[0006] In view of the above defects in the prior art, the present invention discloses a novel bandgap reference voltage source.

[0007] The novel bandgap reference voltage source of the present invention comprises a first PNP tube and a second PNP tube, wherein the bases and collectors of the two PNP tubes are grounded, and the emitters are connected to a negative feedback circuit;

[0008] The negative feedback circuit includes a first P tube and a second P tube whose sources are connected to a power supply, the gates of the first P tube and the second P tube are connected and connected to the drain of the second P tube, the drains of the first P tube and the second P tube are respectively connected to the sources of the third P tube and the fourth P tube, the gates of the third P tube and the fourth P tube are connected and connected to the drain of the fourth P tube, the drains of the third P tube and the fourth P tube are respectively connected to the drains of the first N tube and the second N tube, the gates of the first N tube and the second N tube are connected and connected to the drain of the first N tube, the sources of the first N tube and the second N tube are respectively connected to the drains of the third N tube and the fourth N tube, the gates of the third N tube and the fourth N tube are connected and connected to the drain of the third N tube, the source of the third N tube is connected to the emitter of the first PNP tube, the source of the fourth N tube is connected to the second resistor and the third resistor, and the other ends of the second resistor and the third resistor are respectively connected to the emitter of the second PNP tube and the ground;

[0009] The width-to-length ratio of the first P tube and the second P tube is equal; the emitter areas of the first PNP tube and the second PNP tube are not equal;

[0010] The negative feedback circuit is also connected to a start-up circuit and a voltage and current output circuit, and the start-up circuit is used to provide a start-up current for the transistor;

[0011] The voltage and current output circuit includes an eighth P tube and a ninth P tube, wherein the sources of the eighth P tube and the ninth P tube are connected to the power supply, the gates are connected to the gate of the first P tube, the drain of the eighth P tube is grounded through a fifth resistor, and the drain of the ninth P tube outputs current.

[0012] Preferably, the startup circuit includes a seventh P tube whose source is connected to the power supply, the drain of the seventh P tube is connected to the first resistor, the other end of the first resistor is connected to the source of the sixth P tube, the drain and gate of the sixth P tube are grounded, the gate of the seventh P tube is connected to the gate of the first P tube, the drain of the seventh P tube is also connected to the gate of the fifth P tube, and the source and drain of the fifth P tube are respectively connected to the power supply and the drain of the first N tube.

[0013] Preferably, the gate of the sixth P transistor is grounded through a resistor.

[0014] Preferably, the sixth P tube is an inverse ratio tube whose length is greater than its width.

[0015] Preferably, the drain of the ninth P tube is also connected to a current replication circuit, and the current replication circuit includes a fifth N tube and a sixth N tube, wherein the gates of the fifth N tube and the sixth N tube are connected and connected to the drain of the fifth N tube, and the drain of the fifth N tube is also connected to the drain of the ninth P tube; the sources of the fifth N tube and the sixth N tube are respectively connected to the drains of the seventh N tube and the eighth N tube, the gates of the seventh N tube and the eighth N tube are connected and connected to the drain of the seventh N tube, the sources of the seventh N tube and the eighth N tube are both grounded, the drain of the sixth N tube is also connected to the gate and drain of the tenth P tube, the source of the tenth P tube is connected to the power supply, the gate is also connected to the eleventh P tube, and the source of the eleventh P tube is connected to the power supply.

[0016] Preferably, the second resistor, the third resistor and the fifth resistor are all polycrystalline resistors.

[0017] Compared with the prior art, the novel bandgap reference voltage source of the present invention has the following advantages:

[0018] 1. There is no need for a clamping operational amplifier in the circuit. Four MOS tubes are used directly instead of the operational amplifier to realize the clamping voltage function. No transistor is required at the output end. A current that is not affected by temperature can be obtained at the front end. By mirroring the current to the output end, a reference voltage that is not affected by temperature can be obtained.

[0019] 2. Since there is no operational amplifier, the circuit is simpler and there is no stability problem caused by the operational amplifier. The theoretical error caused by the inherent offset voltage and limited gain of the operational amplifier is also eliminated, and the accuracy is higher.

[0020] 3. Since there is no transistor in the output stage, the output value is not the traditional 1.25V, and the power supply voltage does not need to be greater than 1.25V. In addition, the voltage value of the reference voltage can be adjusted by adjusting the resistance value and the input current value, which has a wider range of applications and more flexible usage conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 FIG. 1 is a schematic diagram showing a specific implementation of the novel bandgap reference voltage source of the present invention;

[0022] Figure 2 Shown is a schematic diagram of a specific implementation of a traditional bandgap reference voltage source;

[0023] Figure 3 Shown is a schematic diagram of a simulation curve of the novel bandgap reference voltage source of the present invention. DETAILED DESCRIPTION

[0024] In order to more intuitively and clearly describe the specific details of the technical solution of the present invention, a detailed description will be given below in conjunction with specific embodiments and example drawings.

[0025] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in combination with the specific implementation methods of the present invention and the corresponding drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] like Figure 1 As shown, the novel bandgap reference voltage source of the present invention comprises a first PNP tube Q1 and a second PNP tube Q2, the bases and collectors of the two PNP tubes are both grounded, and the emitters are connected to a negative feedback circuit;

[0027] The negative feedback circuit includes a first P tube PM1 and a second P tube PM2 whose sources are connected to a power supply, the gates of the first P tube and the second P tube are connected and connected to the drain of the second P tube, the drains of the first P tube and the second P tube are respectively connected to the sources of the third P tube and the fourth P tube, the gates of the third P tube and the fourth P tube are connected and connected to the drain of the fourth P tube, the drains of the third P tube and the fourth P tube are respectively connected to the drains of the first N tube NM1 and the second N tube NM2, the gates of the first N tube and the second N tube are connected and connected to the drain of the first N tube, the sources of the first N tube and the second N tube are respectively connected to the drains of the third N tube NM3 and the fourth N tube NM4, the gates of the third N tube and the fourth N tube are connected and connected to the drain of the third N tube, the source of the third N tube is connected to the emitter of the first PNP tube, the source of the fourth N tube is connected to the second resistor R2 and the third resistor R3, and the other ends of the second resistor R2 and the third resistor R3 are respectively connected to the emitter of the second PNP tube Q2 and the ground;

[0028] The first P tube and the second P tube have the same width-to-length ratio; the third N tube and the fourth N tube have the same width-to-length ratio;

[0029] Since the gate and source potentials of the first P-tube and the second P-tube are respectively equal, that is, the gate-source voltage difference between the two is equal, and the width-to-length ratios of the two are equal, the currents flowing through the first P-tube and the second P-tube are equal, and the width-to-length ratios of the third N-tube and the fourth N-tube are equal, the currents are equal, so the gate-source voltages of the third N-tube and the fourth N-tube are equal, and the gates of the third N-tube and the fourth N-tube are interconnected, so that the source voltages of the third N-tube and the fourth N-tube are equal.

[0030] The first N-tube NM1, the second N-tube NM2, the third P-tube PM3 and the fourth P-tube PM4 form a group of isolation tubes, which can isolate the first P-tube PM1 and the second P-tube PM2 as the current source reference, increase the output resistance of the negative feedback loop, and improve the feedback accuracy.

[0031] The conventional bandgap reference source operational amplifier has no reference current source, so it needs to use self-biasing to provide current, which has poor stability. The single-ended operational amplifier has poor PSSR (power supply rejection ratio), which will introduce power supply errors. At the same time, the operational amplifier needs high gain to obtain low offset voltage, which consumes a lot of power. The present invention only uses 4 MOS tubes to form a current negative feedback loop, so that the source end voltage is equal, and has a simple structure and low power consumption.

[0032] Due to the negative feedback circuit, the voltages at the sources of the third N-tube NM3 and the fourth N-tube NM4 are equal, that is, VS3=VS4, where VS3 and VS4 represent the voltages at the sources of the third N-tube and the fourth N-tube, respectively.

[0033] And VS3 is obviously equal to the base-collector voltage VBE1 of the first PNP tube Q1, that is, VS3=VS4=VBE1.

[0034] At the same time, due to the width-to-length ratio of the first P-tube PM1 and the second P-tube PM2, and the gate and source voltages of the two are equal, the currents of the first P-tube PM1 and the second P-tube PM2 are the same, and VS3 = VS4, the current flowing through the second resistor R2 is

[0035]

[0036] Where ΔVBE=VBE1-VBE2, N is the emitter area ratio of the second PNP tube Q2 and the first PNP tube Q1, VT= is the thermal voltage, which is a negative temperature coefficient voltage, and VBE1 and VBE2 are the base-collector voltages of the first and second PNP tubes respectively;

[0037] At the same time, the current I flowing through resistor R3 R3 =VS4 / R3, that is, I R3 =VBE1 / R3, where VBE1 is the base-collector voltage of the first PNP tube, which is a positive temperature coefficient voltage.

[0038] The current I flowing through the second P tube p2 is the sum of the currents flowing through resistors R2 and R3,

[0039] I p2 =I R2 +I R3

[0040]

[0041] By designing the ratio of the two resistors R2 and R3 and considering the emitter area ratio N of the second PNP tube Q2 and the first PNP tube Q1, the current I flowing through the second P tube can be p2 The temperature coefficient is zero. p2 Can be used as a reference current with zero temperature coefficient.

[0042] Since each resistor in the integrated circuit process can be made of polycrystalline resistors with a very low temperature coefficient, after eliminating the temperature change of the resistor, the current with a temperature coefficient of zero can be used to output a reference voltage with a temperature coefficient of zero through current mirror replication in the voltage and current output circuit and flowing through the resistor.

[0043] The voltage and current output circuit comprises an eighth P-tube PM8 and a ninth P-tube PM9, wherein the sources of the eighth P-tube and the ninth P-tube are connected to the power supply, the gates are connected to the gate of the first P-tube PM1, the drain of the eighth P-tube is grounded through a fifth resistor R5, and the drain of the ninth P-tube is connected to the current replication circuit;

[0044] The eighth P tube is used to output the reference voltage VREF. Since the gate of the eighth P tube is connected to the second P tube, and the sources of the two are connected to the power supply, the two form a current mirror, that is, the current of the eighth P tube

[0045] I p8 =K*I p2

[0046] K is the ratio of the width to length ratio of the eighth P-tube to the second P-tube, and the reference voltage VREF is the current of the eighth P-tube P8 multiplied by the fifth resistor R5.

[0047] Reference voltage VREF=R5*I p8 =R5*K*I p2 .

[0048] Figure 1 In the specific embodiment shown, the reference voltage

[0049] It can be seen from the above formula that by setting the ratio K of the width-to-length ratios of the eighth P-tube PM8 and the second P-tube PM2, and the resistance value of the resistor R5, the value of the reference voltage VREF can be adjusted. The reference voltage is proportional to the generated reference current. When the reference current has a zero temperature coefficient, the temperature coefficient of the resistor is ignored, and a reference voltage with a zero temperature coefficient can also be obtained. The voltage value of the reference voltage is not limited to the traditional bandgap reference voltage of 1.25V, and has a larger adjustment range.

[0050] The ninth P-tube PM9 and the second P-tube PM2 also form a current mirror, and the ninth P-tube can directly output a reference current with a zero temperature coefficient. Figure 1 In the specific implementation shown, the reference voltage output terminal is connected to a sixth resistor. The function of the sixth resistor is that the reference voltage output terminal may be directly connected to an external pin during testing. The sixth resistor R6 is added to prevent ESD voltage from damaging the internal circuit.

[0051] Figure 1In the specific implementation manner shown, a current replication circuit is also included, which includes a fifth N-tube NM5 and a sixth N-tube NM6, wherein the gates of the fifth N-tube NM5 and the sixth N-tube NM6 are connected to each other and to the drain of the fifth N-tube, and the drain of the fifth N-tube NM5 is also connected to the drain of the ninth P-tube PM9; the sources of the fifth N-tube and the sixth N-tube are respectively connected to the drains of the seventh N-tube NM7 and the eighth N-tube NM8, the gates of the seventh N-tube and the eighth N-tube are connected to each other and to the drain of the seventh N-tube NM7, the sources of the seventh N-tube and the eighth N-tube are both grounded, the drain of the sixth N-tube is also connected to the gate and drain of the tenth P-tube PM10, the source of the tenth P-tube PM10 is connected to the power supply, and the gate is also connected to the eleventh P-tube PM11, the source of the eleventh P-tube PM11 is connected to the power supply, and the drain is connected to the current output terminal IREF to output current. The fifth to eighth N transistors form an NMOS current mirror, and the tenth P transistor PM10 and the eleventh P transistor P11 form a PMOS current mirror, so as to achieve accurate replication of the current.

[0052] The negative feedback circuit is also connected to a start-up circuit and a voltage and current output circuit, and the start-up circuit is used to provide a start-up current for the transistor;

[0053] like Figure 1 In the specific implementation manner shown, the startup circuit includes a seventh P-tube PM7 whose source is connected to a power supply, a drain of the seventh P-tube PM7 is connected to a first resistor R1, the other end of the first resistor R1 is connected to a source of a sixth P-tube PM6, a drain and a gate of the sixth P-tube PM6 are grounded, the gate of the seventh P-tube is connected to the gate of the first P-tube PM1, the drain of the seventh P-tube PM7 is also connected to the gate of the fifth P-tube PM5, and the source and drain of the fifth P-tube are respectively connected to the power supply and the drain of the first N-tube;

[0054] The sixth P-tube PM6 usually adopts an inverse ratio tube with a length much larger than a width to play the role of a resistor. The bias voltage of the seventh P-tube PM7 is generated by the second P-tube PM2. In the initial state of power-on, the gate bias voltage of the second P-tube is not formed, and the gate voltage of the fifth P-tube is pulled down by the pull-down branch composed of the first resistor and the sixth P-tube. The fifth P-tube is first turned on to form a current flowing into the first N-tube. After the first N-tube NM1 generates a current, the current is mirrored to the second P-tube through the second N-tube NM2, the fourth P-tube PM4 and the second P-tube PM2. The gate of the second P-tube generates a bias voltage, so that the seventh P-tube is turned on. After the seventh P-tube is turned on, since the resistance R1 connected to the drain of the seventh P-tube and the equivalent resistance in series of the sixth P-tube are relatively large, the gate voltage of the fifth P-tube PM5 increases, so that the fifth P-tube is turned off, and the startup circuit stops working. Only the seventh P-tube PM7 has a small current to maintain, thereby reducing the DC power consumption of the startup circuit. Figure 1In the specific implementation shown, the gate of the sixth P transistor PM6 is grounded through a first resistor R1. The first resistor R1 is used to prevent the ESD current introduced into the ground pin during testing from damaging the gate of the sixth P transistor.

[0055] like Figure 3 A simulation curve of the reference voltage is shown as follows. Figure 3 The horizontal axis is temperature in degrees Celsius, and the vertical axis is the reference voltage value in volts. In the range of -40 to +125 degrees Celsius, the reference voltage value is maintained between 1.873-1.913V, and the reference voltage drift is 40 millivolts. The reference value is significantly larger than the traditional bandgap reference voltage of 1.25V, and the temperature drift is controlled at about 2%.

[0056] The foregoing describes various preferred embodiments of the present invention. Unless the preferred implementation modes in various preferred embodiments are obviously self-contradictory or based on a certain preferred implementation mode, various preferred implementation modes can be arbitrarily superimposed and used in combination. The embodiments and specific parameters in the embodiments are only for clearly describing the invention verification process of the inventor, and are not used to limit the patent protection scope of the present invention. The patent protection scope of the present invention shall still be based on its claims. All equivalent structural changes made using the contents of the description and drawings of the present invention should be included in the protection scope of the present invention.

Claims

1. A new type of bandgap reference voltage source, characterized in that , including a first PNP tube and a second PNP tube, the bases and collectors of the two PNP tubes are grounded, and the emitters are connected to a negative feedback circuit; The negative feedback circuit includes a first P tube and a second P tube whose sources are connected to a power supply, the gates of the first P tube and the second P tube are connected and connected to the drain of the second P tube, the drains of the first P tube and the second P tube are respectively connected to the sources of the third P tube and the fourth P tube, the gates of the third P tube and the fourth P tube are connected and connected to the drain of the fourth P tube, the drains of the third P tube and the fourth P tube are respectively connected to the drains of the first N tube and the second N tube, the gates of the first N tube and the second N tube are connected and connected to the drain of the first N tube, the sources of the first N tube and the second N tube are respectively connected to the drains of the third N tube and the fourth N tube, the gates of the third N tube and the fourth N tube are connected and connected to the drain of the third N tube, the source of the third N tube is connected to the emitter of the first PNP tube, the source of the fourth N tube is connected to the second resistor and the third resistor, and the other ends of the second resistor and the third resistor are respectively connected to the emitter of the second PNP tube and the ground; The width-to-length ratio of the first P tube and the second P tube is equal; the emitter areas of the first PNP tube and the second PNP tube are not equal; The negative feedback circuit is also connected to a start-up circuit and a voltage and current output circuit, and the start-up circuit is used to provide a start-up current for the transistor; The voltage and current output circuit includes an eighth P tube and a ninth P tube, wherein the sources of the eighth P tube and the ninth P tube are connected to the power supply, the gates are connected to the gate of the first P tube, the drain of the eighth P tube is grounded through a fifth resistor, and the drain of the ninth P tube outputs current.

2. The novel bandgap reference voltage source as claimed in claim 1, characterized in that: The startup circuit includes a seventh P tube whose source is connected to a power supply, a drain of the seventh P tube is connected to a first resistor, the other end of the first resistor is connected to the source of a sixth P tube, the drain and gate of the sixth P tube are grounded, the gate of the seventh P tube is connected to the gate of the first P tube, the drain of the seventh P tube is also connected to the gate of the fifth P tube, and the source and drain of the fifth P tube are respectively connected to the power supply and the drain of the first N tube.

3. The novel bandgap reference voltage source as claimed in claim 2, characterized in that: The gate of the sixth P transistor is grounded through a resistor.

4. The novel bandgap reference voltage source as claimed in claim 2, characterized in that: The sixth P tube is an inverse ratio tube whose length is greater than its width.

5. The novel bandgap reference voltage source as claimed in claim 1, characterized in that: The drain of the ninth P tube is also connected to a current replication circuit, which includes a fifth N tube and a sixth N tube, wherein the gates of the fifth N tube and the sixth N tube are connected and connected to the drain of the fifth N tube, and the drain of the fifth N tube is also connected to the drain of the ninth P tube; the sources of the fifth N tube and the sixth N tube are respectively connected to the drains of the seventh N tube and the eighth N tube, the gates of the seventh N tube and the eighth N tube are connected and connected to the drain of the seventh N tube, the sources of the seventh N tube and the eighth N tube are both grounded, the drain of the sixth N tube is also connected to the gate and drain of the tenth P tube, the source of the tenth P tube is connected to a power supply, the gate is also connected to the eleventh P tube, and the source of the eleventh P tube is connected to the power supply.

6. The novel bandgap reference voltage source as claimed in claim 1, characterized in that: The second resistor, the third resistor and the fifth resistor are all polycrystalline resistors.

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