A bandgap reference circuit

Abstract

The application relates to the field of integrated circuit technology and discloses a band gap reference circuit, which comprises a positive temperature coefficient current generating circuit, a compensation circuit and a band gap reference voltage generating circuit; the first end of the positive temperature coefficient current generating circuit is connected with a power supply, the second end is grounded, the third end is connected with the first end of the compensation circuit, the fourth end is connected with the second end of the compensation circuit, the fifth end is connected with the fifth end of the compensation circuit, and the positive temperature coefficient current is generated; the third end of the compensation circuit is connected with the power supply, and the fourth end is grounded; the first end of the band gap reference voltage generating circuit is connected with the power supply, the second end is grounded, the third end is an output voltage end, and the fourth end is connected with the fifth end of the positive temperature coefficient current generating circuit; the compensation circuit generates a compensation current for compensating the positive temperature coefficient current, and the band gap reference voltage is generated through the band gap reference voltage generating circuit; the temperature coefficient of the band gap reference voltage is compensated through the compensation circuit, and the temperature coefficient of the band gap reference voltage is reduced.

Description

Technical Field

[0001] This invention relates to the field of integrated circuit technology, and more specifically to a bandgap reference circuit. Background Technology

[0002] Voltage or current reference circuits provide a voltage or current source that remains unchanged with temperature and power supply, and the accuracy of the reference has an increasingly significant impact on system performance. Bandgap reference circuits have gained widespread application due to their advantages such as low temperature coefficient, high power supply rejection ratio, and compatibility with traditional CMOS processes.

[0003] Figure 1 This is a schematic diagram of a traditional bandgap reference circuit, showing the difference V between the emitter and base voltages of two PNP transistors Q1 and Q2. BE2 -V BE1 =V T lnn has a positive temperature coefficient, and this voltage can be used to generate a positive temperature coefficient current. A positive temperature coefficient current flowing through R2 generates a positive temperature coefficient voltage. Positive temperature coefficient voltage and negative temperature coefficient voltage V BE3 The summation yields a bandgap reference voltage that varies little with temperature. The temperature coefficient of the bandgap reference can be adjusted by changing the values ​​of resistors R1 and R2. This is because the transistor V... BE It has high-order nonlinearity, which results in a relatively high temperature coefficient of the generated bandgap reference voltage, typically between 10 and 20 ppm / ℃. Summary of the Invention

[0004] In view of this, the present invention provides a bandgap reference circuit to solve the problem of high temperature coefficient of the bandgap reference voltage output by traditional bandgap reference circuits.

[0005] In a first aspect, the present invention provides a bandgap reference circuit, comprising: a positive temperature coefficient current generating circuit, a compensation circuit, and a bandgap reference voltage generating circuit, wherein...

[0006] The positive temperature coefficient current generating circuit has its first terminal connected to the power supply, its second terminal grounded, its third terminal connected to the first terminal of the compensation circuit, its fourth terminal connected to the second terminal of the compensation circuit, and its fifth terminal connected to the fifth terminal of the compensation circuit. It is used to generate the initial bandgap reference voltage.

[0007] The compensation circuit has its third terminal connected to the power supply and its fourth terminal grounded.

[0008] The bandgap reference voltage generating circuit has its first terminal connected to the power supply, its second terminal grounded, its third terminal as the output voltage terminal, and its fourth terminal connected to the fifth terminal of the positive temperature coefficient current generating circuit.

[0009] The compensation circuit generates a negative temperature coefficient compensation current, which is used to compensate for the temperature coefficient of the positive temperature coefficient current. The compensated positive temperature coefficient current is then mirrored to the bandgap reference voltage generation circuit to obtain the bandgap reference voltage and output it.

[0010] The bandgap reference circuit provided by the present invention generates a negative temperature coefficient compensation current through a compensation circuit to compensate for the temperature coefficient of the positive temperature coefficient current generation circuit, and generates and outputs a bandgap reference voltage through a bandgap reference voltage generation circuit, thereby reducing the temperature coefficient of the bandgap reference voltage.

[0011] In one optional implementation, the positive temperature coefficient current generating circuit includes: a first transistor, a second transistor, a first operational amplifier, a third transistor, a fourth transistor, a fifth transistor, a sixth transistor, and a first resistor, wherein,

[0012] The first transistor has its control terminal connected to the control terminal of the second transistor and the output terminal of the first operational amplifier, its first terminal connected to the non-inverting input terminal of the first operational amplifier and the first terminal of the first resistor, and its second terminal connected to the second terminal of the second transistor and the power supply.

[0013] The first terminal of the second transistor is connected to the inverting input terminal of the first operational amplifier and the second terminal of the fourth transistor;

[0014] The third transistor has its control terminal connected to the first terminal of the compensation circuit and the second terminal of the fifth transistor. Its second terminal is connected to the second terminal of the first resistor, and its first terminal is grounded.

[0015] The fourth transistor has its control terminal connected to the second terminal of the compensation circuit and the second terminal of the sixth transistor, while its first terminal is grounded.

[0016] The fifth transistor has its control terminal connected to the control terminal of the sixth transistor, and both its control terminal and its first terminal are grounded.

[0017] The sixth transistor has its first terminal grounded.

[0018] The bandgap reference circuit provided by this invention improves the input voltage of the first operational amplifier by superimposing the third and fifth transistors and the fourth and sixth transistors, thereby reducing the influence of the offset voltage of the first operational amplifier on the positive temperature coefficient current and improving the accuracy of the bandgap reference voltage.

[0019] In one optional implementation, the compensation circuit includes: a seventh transistor, an eighth transistor, a ninth transistor, a tenth transistor, an eleventh transistor, a twelfth transistor, a thirteenth transistor, and a second resistor, wherein,

[0020] The seventh transistor has its control terminal connected to the control terminals of the eighth and tenth transistors, its first terminal connected to the third terminal of the positive temperature coefficient current generating circuit, and its second terminal connected to the power supply.

[0021] The eighth transistor has its first terminal connected to the fourth terminal of the positive temperature coefficient current generating circuit, and its second terminal connected to the power supply.

[0022] The ninth transistor has its control terminal connected to the fifth terminal of the positive temperature coefficient current generating circuit, its first terminal connected to the first terminal of the eleventh transistor, and its second terminal connected to the power supply.

[0023] The tenth transistor has its control terminal connected to its first terminal and the first terminal of the twelfth transistor, and its second terminal connected to the power supply.

[0024] The eleventh transistor has its control terminal connected to its first terminal and the control terminal of the twelfth transistor, and its second terminal connected to the second terminal of the thirteenth transistor.

[0025] The twelfth transistor has its second terminal connected to the first terminal of the second resistor;

[0026] The thirteenth transistor has its control terminal connected to its first terminal and grounded.

[0027] The second resistor has its second terminal grounded.

[0028] The voltage at the second terminal of the twelfth transistor is applied to the second resistor, and the current through the second resistor is the compensation current.

[0029] The bandgap reference circuit provided by the present invention generates a compensation current through a compensation circuit, and injects the compensation current into the positive temperature coefficient current generating circuit through the seventh and eighth transistors of the current mirror.

[0030] In one alternative implementation, the eleventh transistor and the twelfth transistor have the same width-to-length ratio of their conductive channels, and the formula for calculating the compensation current is:

[0031]

[0032] Among them, I CTAT V represents the compensation current with a negative temperature coefficient. BE13 R1 represents the voltage between the control terminal and the second terminal of the thirteenth transistor, and R2 represents the resistance value of the second resistor.

[0033] The bandgap reference circuit provided by this invention, when the width-to-length ratio of the conductive channels of the eleventh transistor and the twelfth transistor in the compensation circuit is the same, the voltage between the control terminal of the eleventh transistor and the second terminal is equal to the voltage between the control terminal of the twelfth transistor and the second terminal. Therefore, the compensation current can be accurately calculated through the thirteenth transistor and the second resistor.

[0034] In one alternative implementation, the ratio of the width-to-length ratio of the seventh transistor's conductive channel to that of the eighth transistor's conductive channel is used to adjust the temperature coefficient of the bandgap reference voltage.

[0035] In one alternative implementation, the process of adjusting the temperature coefficient of the bandgap reference voltage includes:

[0036] Calculate the relationship between bandgap reference voltage and temperature:

[0037]

[0038] in, This indicates the relationship between the bandgap reference voltage and temperature. This indicates the voltage-temperature relationship between the control terminal and the second terminal of the fifteenth transistor. This indicates the relationship between the voltage generated by a positive temperature coefficient current passing through a third resistor and the temperature.

[0039] Adjust the ratio of the width-to-length ratio of the seventh transistor's conductive channel to that of the eighth transistor's conductive channel, so that... The temperature coefficient of the bandgap reference voltage is then 0.

[0040] The bandgap reference circuit provided by this invention changes the relationship between the positive temperature coefficient current and temperature by adjusting the ratio of the width-to-length ratio of the seventh transistor's conductive channel to that of the eighth transistor's conductive channel, thereby reducing the relationship between the output bandgap reference voltage and temperature and lowering the temperature coefficient of the bandgap reference voltage.

[0041] In one alternative implementation, the bandgap reference voltage generation circuit includes: a fourteenth transistor, a third resistor, and a fifteenth transistor, wherein,

[0042] The fourteenth transistor has its control terminal connected to the fifth terminal of the positive temperature coefficient current generating circuit, its first terminal connected to the first terminal of the third resistor, and its second terminal connected to the power supply.

[0043] The third resistor has its second terminal connected to the second terminal of the fifteenth transistor, and its first terminal outputs a bandgap reference voltage.

[0044] The fifteenth transistor has its control terminal connected to its first terminal and grounded.

[0045] The bandgap reference circuit provided by this invention reduces the temperature coefficient of the output bandgap reference voltage by complementing the temperature-dependent voltage effects of the voltage generated by the fifteenth transistor with the temperature-dependent positive temperature coefficient current output by the compensation circuit and the positive temperature coefficient current generation circuit, as well as the temperature-dependent voltage effects of the voltage generated by the third resistor.

[0046] In one alternative implementation, the first transistor, the second transistor, the seventh transistor, the eighth transistor, the ninth transistor, the tenth transistor, and the fourteenth transistor are P-type MOS transistors, the eleventh transistor and the twelfth transistor are N-type MOS transistors, and the third transistor, the fourth transistor, the fifth transistor, the sixth transistor, the thirteenth transistor, and the fifteenth transistor are bipolar transistors.

[0047] The bandgap reference circuit provided by this invention optimizes the compensation effect of the compensation circuit by selecting different types of transistors, ensuring that the temperature coefficient of the bandgap reference voltage output by the bandgap reference circuit is minimized. Attached Figure Description

[0048] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0049] Figure 1 This is a schematic diagram of a traditional bandgap reference circuit;

[0050] Figure 2 This is a schematic diagram of a bandgap reference circuit according to an embodiment of the present invention;

[0051] Figure 3 This is a schematic diagram of a specific embodiment of a bandgap reference circuit according to an embodiment of the present invention;

[0052] Figure 4 This is a schematic diagram of another specific embodiment of a bandgap reference circuit according to an embodiment of the present invention;

[0053] Figure 5 This is a schematic diagram illustrating the change of the derivative of the bandgap reference voltage with respect to temperature before and after compensation in a bandgap reference circuit according to an embodiment of the present invention.

[0054] Figure 6 This is a schematic diagram comparing the relationship between bandgap reference voltage and temperature before and after compensation in a bandgap reference circuit according to an embodiment of the present invention. Detailed Implementation

[0055] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0056] This invention provides a bandgap reference circuit that generates a compensation current through a compensation circuit to compensate for the temperature coefficient of the positive temperature coefficient current generated by the positive temperature coefficient current generation circuit, thereby reducing the temperature coefficient of the bandgap reference voltage.

[0057] This embodiment provides a bandgap reference circuit. Figure 2 This is a schematic diagram of a bandgap reference circuit according to an embodiment of the present invention, as shown below. Figure 2 As shown, the bandgap reference circuit includes: a positive temperature coefficient current generating circuit 1, a compensation circuit 2, and a bandgap reference voltage generating circuit 3.

[0058] like Figure 2 As shown, the positive temperature coefficient current generating circuit 1 has its first terminal connected to the power supply, its second terminal grounded, its third terminal connected to the first terminal of the compensation circuit 2, its fourth terminal connected to the second terminal of the compensation circuit 2, and its fifth terminal connected to the fifth terminal of the compensation circuit 2. It is used to generate a positive temperature coefficient current.

[0059] like Figure 2 As shown, compensation circuit 2 has its third terminal connected to the power supply and its fourth terminal grounded.

[0060] like Figure 2 As shown, the bandgap reference voltage generating circuit 3 has its first terminal connected to the power supply, its second terminal grounded, and its third terminal being the output voltage terminal V. BG Its fourth terminal is connected to the fifth terminal of the positive temperature coefficient current generating circuit 1.

[0061] The compensation circuit 2 generates a negative temperature coefficient compensation current, which is used to compensate for the temperature coefficient of the positive temperature coefficient current, resulting in a compensated positive temperature coefficient current. The compensated positive temperature coefficient current is then mirrored to the bandgap reference voltage generation circuit 3 to obtain the bandgap reference voltage and output it.

[0062] V BG =V BE15 +V PTAT V BE15 V is the voltage difference between the second terminal and the control terminal of the fifteenth transistor. PTAT The voltage generated by the positive temperature coefficient current flowing through the third resistor.

[0063] Specifically, the nonlinear characteristic of the voltage between the control terminal and the second terminal of the transistor with temperature is as follows:

[0064]

[0065] Among them, V BE (T) represents the voltage value between the control terminal and the second terminal of the transistor at temperature T, V G0 T represents the voltage between the control terminal and the second terminal of the transistor when the temperature is absolute zero. r The reference temperature is represented by k, the Boltzmann constant by k, the charge per unit electron by q, η by η being a constant and η≈4, and m by the current I flowing through the first and second terminals of the transistor. C The corresponding temperature index and I C With T m Proportional.

[0066] For V BE (T) Differentiation yields:

[0067]

[0068] in, As a constant, η-m>0, It decreases as temperature T increases, therefore It has a negative temperature coefficient.

[0069] From the above analysis, we can see that V BE The derivative of voltage with respect to temperature has a negative temperature coefficient, before compensation. Since the constant value, the derivative of the bandgap reference voltage with respect to temperature before compensation has a negative temperature coefficient. After the compensation circuit 2 generates a compensation current, it is injected into the positive temperature coefficient current generating circuit 1 through the first and second terminals of the compensation circuit 2 to compensate for the temperature coefficient of the positive temperature coefficient current of the positive temperature coefficient current generating circuit 1, thus obtaining a compensated positive temperature coefficient current. The compensated positive temperature coefficient current is then mirrored onto the bandgap reference voltage generating circuit 3, thereby reducing the temperature coefficient of the bandgap reference voltage obtained by the bandgap reference voltage generating circuit 3.

[0070] The bandgap reference circuit provided by the present invention generates a negative temperature coefficient compensation current through the compensation circuit 2 to compensate for the temperature coefficient of the positive temperature coefficient current, and generates and outputs a bandgap reference voltage through the bandgap reference voltage generation circuit, thereby reducing the temperature coefficient of the bandgap reference voltage.

[0071] In some alternative implementations, such as Figure 3As shown, the positive temperature coefficient current generating circuit 1 includes: a first transistor M1, a second transistor M2, a first operational amplifier OP1, a third transistor M3, a fourth transistor M4, a fifth transistor M5, a sixth transistor M6, and a first resistor R1.

[0072] like Figure 3 As shown, the first transistor M1 has its control terminal connected to the control terminal of the second transistor M2 and the output terminal of the first operational amplifier OP1. Its first terminal is connected to the non-inverting input terminal of the first operational amplifier OP1 and the first terminal of the first resistor R1. Its second terminal is connected to the second terminal of the second transistor M2 and the power supply. The second transistor M2 has its first terminal connected to the inverting input terminal of the first operational amplifier OP1 and the second terminal of the fourth transistor M4. The third transistor M3 has its control terminal connected to the first terminal of the compensation circuit 2 and the second terminal of the fifth transistor M5. Its second terminal is connected to the second terminal of the first resistor R1, and its first terminal is grounded. The fourth transistor M4 has its control terminal connected to the second terminal of the compensation circuit 2 and the second terminal of the sixth transistor M6, and its first terminal is grounded. The fifth transistor M5 has its control terminal connected to the control terminal of the sixth transistor M6, and both its control terminal and its first terminal are grounded. The sixth transistor M6 has its first terminal grounded.

[0073] Specifically, transistors M3, M4, M5, and M6 are bipolar junction transistors (BJTs). The ratio of the emitter areas of transistor M3 to M4 is n1, and the ratio of the emitter areas of transistor M5 to M6 is n2. The voltage difference generated by the four transistors is:

[0074] ΔV BE =V T lnn1+V T lnn2 (3)

[0075] Among them, V T Indicates thermal voltage k represents the Boltzmann constant, q represents the charge per unit charge, and T represents the temperature.

[0076] The superposition of two transistors increases the input voltage of the first operational amplifier, reducing the impact of the first operational amplifier's offset voltage on the positive temperature coefficient current generation circuit and improving the accuracy of the positive temperature coefficient current. Without considering the compensation circuit, the initial positive temperature coefficient current flowing through the first resistor is:

[0077]

[0078] Among them, I PTAT R1 represents the initial positive temperature coefficient current flowing through the first resistor, and R1 represents the resistance value of the first resistor.

[0079] The bandgap reference circuit provided in this embodiment improves the input voltage of the first operational amplifier by superimposing the third transistor M3 and the fifth transistor M5, and the fourth transistor M4 and the sixth transistor M6, thereby reducing the impact of the offset voltage of the first operational amplifier on the positive temperature coefficient current generation circuit.

[0080] In some alternative implementations, such as Figure 3 As shown, the compensation circuit 2 includes: a seventh transistor M7, an eighth transistor M8, a ninth transistor M9, a tenth transistor M10, an eleventh transistor M11, a twelfth transistor M12, a thirteenth transistor M13, and a second resistor.

[0081] like Figure 3 As shown, the seventh transistor M7 has its control terminal connected to the control terminals of the eighth transistor M8 and the tenth transistor M10. Its first terminal is connected to the third terminal of the positive temperature coefficient current generating circuit 1, and its second terminal is connected to the power supply. The eighth transistor M8 has its first terminal connected to the fourth terminal of the positive temperature coefficient current generating circuit 1, and its second terminal is connected to the power supply. The ninth transistor M9 has its control terminal connected to the fifth terminal of the positive temperature coefficient current generating circuit 1. Its first terminal is connected to the first terminal of the eleventh transistor M11, and its second terminal is connected to the power supply. The tenth transistor M10 has its control terminal connected to its first terminal and the first terminal of the twelfth transistor M12, and its second terminal is connected to the power supply. The eleventh transistor M11 has its control terminal connected to its first terminal and the control terminal of the twelfth transistor M12, and its second terminal is connected to the second terminal of the thirteenth transistor M13. The twelfth transistor M12 has its second terminal connected to the first terminal of the second resistor. The thirteenth transistor M13 has its control terminal connected to its first terminal and grounded. The second resistor has its second terminal grounded. The voltage at the second terminal of the twelfth transistor M12 is applied to the second resistor, and the current through the second resistor is the compensation current.

[0082] Specifically, transistors M7, M8, M9, and M10 are P-type MOSFETs; M11 and M12 are N-type MOSFETs; and M13 is a transistor. The current generated by the positive temperature coefficient current generating circuit 1 is mirrored to transistor M9. Transistor M9 then generates current for transistors M11 and M13. Transistor M11 turns on transistor M12, and the voltage at the second terminal of transistor M12 is applied to the second resistor R2, generating a compensation current. This compensation current passes through the control terminal and the first terminal of transistor M10, and then through the current mirrors M7 and M8 to inject the compensation current into the positive temperature coefficient current generating circuit 1.

[0083] The bandgap reference circuit provided in this embodiment generates a compensation current through the compensation circuit 2, and injects the compensation current into the positive temperature coefficient current generation circuit 1 through the current mirror seventh transistor M7 and the eighth transistor M8, thereby reducing the temperature coefficient of the output bandgap reference voltage.

[0084] In some alternative implementations, the formula for calculating the compensation current is:

[0085]

[0086] Among them, I CTAT V represents the compensation current with a negative temperature coefficient. BE13 This represents the voltage between the control terminal and the second terminal of the thirteenth transistor M13, R2 represents the resistance value of the second resistor, V GS11 This represents the voltage value between the control terminal and the second terminal of the eleventh transistor M11, V. GS12 This represents the voltage value between the control terminal and the second terminal of the twelfth transistor M12. Since the width-to-length ratio of the conductive channels of the eleventh transistor M11 and the twelfth transistor M12 is the same, V... GS11 =V GS12 The formula for calculating the negative temperature coefficient compensation current is simplified to:

[0087]

[0088] The compensation current is injected into the second terminals of the fifth transistor M5 and the sixth transistor M6 through the current mirrors seventh transistor M7 and eighth transistor M8, respectively. The current values ​​injected into the fifth transistor M5 and the sixth transistor M6 are determined by the ratio of the width-to-length ratio of the conductive channels of the seventh transistor M7 and the eighth transistor M8. Specifically, the larger the width-to-length ratio of the conductive channels of the transistors, the larger the saturation current of the transistors. The ratio of the current values ​​injected into the fifth transistor M5 and the sixth transistor M6 is equal to the ratio of the width-to-length ratio of the conductive channels of the seventh transistor M7 and the eighth transistor M8.

[0089] In the bandgap reference circuit provided in this embodiment, when the width-to-length ratio of the conductive channels of the eleventh transistor M11 and the twelfth transistor M12 in the compensation circuit 2 is the same, the voltage between the control terminal and the second terminal of the eleventh transistor M11 is equal to the voltage between the control terminal and the second terminal of the twelfth transistor M12. Therefore, the compensation current can be accurately calculated through the thirteenth transistor M13 and the second resistor.

[0090] In some alternative implementations, such as Figure 3As shown, the bandgap reference voltage generation circuit 3 includes: a fourteenth transistor M14, a third resistor, and a fifteenth transistor M15. The control terminal of the fourteenth transistor M14 is connected to the fifth terminal of the positive temperature coefficient current generation circuit 1, its first terminal is connected to the first terminal of the third resistor, and its second terminal is connected to the power supply. The second terminal of the third resistor is connected to the second terminal of the fifteenth transistor M15, and its first terminal outputs the bandgap reference voltage. The control terminal of the fifteenth transistor M15 is connected to its first terminal and grounded.

[0091] The bandgap reference circuit provided in this embodiment reduces the temperature coefficient of the output bandgap reference voltage by complementing the temperature-dependent voltage effects of the voltage generated by the fifteenth transistor M15 with the temperature-dependent positive temperature coefficient current output by the compensation circuit 2, the positive temperature coefficient current generation circuit 1, and the voltage generated by the third resistor R3.

[0092] In some alternative implementations, such as Figure 4 As shown, transistors M1, M2, M7, M8, M9, M10, and M14 are P-type MOSFETs; M11 and M12 are N-type MOSFETs; and M3, M4, M5, M6, M13, and M15 are transistors. The transistor types shown here are merely examples and are not exhaustive.

[0093] The bandgap reference circuit provided in this embodiment optimizes the compensation effect of the compensation circuit 2 by selecting different types of transistors, ensuring the lowest temperature coefficient of the bandgap reference voltage.

[0094] In some alternative implementations, the ratio of the aspect ratio of the seventh transistor M7 conductive channel to the aspect ratio of the eighth transistor M8 conductive channel is used to adjust the temperature coefficient of the bandgap reference voltage.

[0095] In some alternative implementations, the process of adjusting the temperature coefficient of the bandgap reference voltage includes:

[0096] Calculate the relationship between bandgap reference voltage and temperature:

[0097]

[0098] in, This indicates the relationship between the bandgap reference voltage and temperature. This indicates the voltage-temperature relationship between the control terminal and the second terminal of the fifteenth transistor. This indicates the relationship between the voltage generated by a positive temperature coefficient current passing through a third resistor and the temperature.

[0099] Adjust the ratio of the width-to-length ratio of the conductive channel of the seventh transistor M7 to the width-to-length ratio of the conductive channel of the eighth transistor M8, so that... The temperature coefficient of the bandgap reference voltage is then 0.

[0100] The bandgap reference circuit provided in this embodiment changes the relationship between the positive temperature coefficient current and temperature by adjusting the ratio of the width-to-length ratio of the conductive channel of the seventh transistor M7 to that of the conductive channel of the eighth transistor M8, thereby reducing the relationship between the output bandgap reference voltage and temperature and lowering the temperature coefficient of the bandgap reference voltage.

[0101] Specifically, the nonlinear characteristic of the voltage between the control terminal and the second terminal of the transistor with respect to temperature is shown in equation (1). Then, the derivative of the voltage between the control terminal and the second terminal of the transistor with respect to temperature is shown in equation (2). It has a negative temperature coefficient.

[0102] In this embodiment, the explanation is based on analyzing the rate of change of the output bandgap reference voltage with temperature before and after adding the compensation circuit:

[0103] (1) Without the addition of a compensation circuit, the current I passing through the third transistor M3, the fourth transistor M4, the fifth transistor M5, and the sixth transistor M6 is... PTAT If they have the same temperature coefficient, then I PTAT for:

[0104]

[0105] If the current is converted into voltage through the third resistor R3 in the bandgap reference voltage generation circuit, and combined with the above formula (4), the voltage across the third resistor R3 in the bandgap reference voltage generation circuit can be obtained as follows:

[0106]

[0107] Differentiating the above bandgap reference voltage with respect to temperature yields the rate of change of the voltage across the third resistor R3 with temperature:

[0108]

[0109] Therefore, we can know It is a constant, such as Figure 5 As shown.

[0110] (2) After adding the compensation circuit, the currents through the third transistor M3 and the fourth transistor M4 have the same temperature coefficient. Since the compensation current is injected into the second terminals of the fifth transistor M5 and the sixth transistor M6 through the current mirrors seventh transistor M7 and eighth transistor M8 respectively, the currents through the fifth transistor M5 and the sixth transistor M6 have different temperature coefficients. Let the current through the fifth transistor M5 be I.C5 With T m2 Proportional to the current I passing through the sixth transistor M6 C6 With T m3 If the voltage across the third resistor R3 is directly proportional to the temperature, then the rate of change of the voltage across R3 with temperature is:

[0111]

[0112] in, If m is a constant, then by adjusting the ratio of the width-to-length ratio of the conductive channel of the seventh transistor M7 to that of the conductive channel of the eighth transistor M8 so that m3 > m2, then... It increases with increasing temperature, therefore It has a positive temperature coefficient.

[0113] Based on the above analysis, the rate of change of the voltage between the control terminal and the second terminal of the fifteenth transistor M15 with temperature is obtained. Having a negative temperature coefficient, the bandgap reference voltage output by the bandgap reference circuit changes with temperature at the following rate:

[0114]

[0115] like Figure 5 As shown, before adding the compensation circuit, the derivative of the output bandgap reference voltage with respect to temperature... The value decreases with increasing temperature. This can be achieved by adjusting the ratio of the width-to-length ratio of the conductive channel of the seventh transistor M7 to that of the conductive channel of the eighth transistor M8. but This reduces the output bandgap reference voltage V. BG Temperature coefficient in actual circuits It cannot be exactly equal to 0, but it will be close to 0. For example... Figure 6 The figure shows the relationship between the output bandgap reference voltage and temperature before and after adding the compensation circuit.

[0116] Although embodiments of the invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the invention, and such modifications and variations all fall within the scope defined by the appended claims.

Claims

1. A bandgap reference circuit, characterized in that, The bandgap reference circuit includes: a positive temperature coefficient current generating circuit, a compensation circuit, and a bandgap reference voltage generating circuit, wherein... A positive temperature coefficient current generating circuit has its first terminal connected to the power supply, its second terminal grounded, its third terminal connected to the first terminal of the compensation circuit, its fourth terminal connected to the second terminal of the compensation circuit, and its fifth terminal connected to the fifth terminal of the compensation circuit. It is used to generate a positive temperature coefficient current. The compensation circuit has its third terminal connected to the power supply and its fourth terminal grounded. The bandgap reference voltage generating circuit has its first terminal connected to the power supply, its second terminal grounded, its third terminal being the output voltage terminal, and its fourth terminal connected to the fifth terminal of the positive temperature coefficient current generating circuit. The compensation circuit generates a negative temperature coefficient compensation current, which is used to compensate for the temperature coefficient of the positive temperature coefficient current. The compensated positive temperature coefficient current is mirrored to the bandgap reference voltage generation circuit to obtain the bandgap reference voltage and output it. The compensation circuit includes: a seventh transistor, an eighth transistor, a ninth transistor, a tenth transistor, an eleventh transistor, a twelfth transistor, a thirteenth transistor, and a second resistor. The seventh transistor has its control terminal connected to the control terminals of the eighth and tenth transistors, its first terminal connected to the third terminal of the positive temperature coefficient current generating circuit, and its second terminal connected to the power supply. The eighth transistor has its first terminal connected to the fourth terminal of the positive temperature coefficient current generating circuit, and its second terminal connected to the power supply. The ninth transistor has its control terminal connected to the fifth terminal of the positive temperature coefficient current generating circuit, its first terminal connected to the first terminal of the eleventh transistor, and its second terminal connected to the power supply. Source connection; the tenth transistor, whose control terminal is connected to its first terminal and the first terminal of the twelfth transistor, and whose second terminal is connected to the power supply; the eleventh transistor, whose control terminal is connected to its first terminal and the control terminal of the twelfth transistor, and whose second terminal is connected to the second terminal of the thirteenth transistor; the twelfth transistor, whose second terminal is connected to the first terminal of the second resistor; the thirteenth transistor, whose control terminal is connected to its first terminal and grounded; the second resistor, whose second terminal is grounded; the voltage of the second terminal of the twelfth transistor is applied to the second resistor, and the current through the second resistor is the compensation current; the compensation current is injected into the second terminals of the fifth transistor and the sixth transistor through the current mirrors seventh and eighth transistors, respectively.

2. The bandgap reference circuit according to claim 1, characterized in that, The positive temperature coefficient current generating circuit includes: a first transistor, a second transistor, a first operational amplifier, a third transistor, a fourth transistor, a fifth transistor, a sixth transistor, and a first resistor, wherein... The first transistor has its control terminal connected to the control terminal of the second transistor and the output terminal of the first operational amplifier, its first terminal connected to the non-inverting input terminal of the first operational amplifier and the first terminal of the first resistor, and its second terminal connected to the second terminal of the second transistor and the power supply. The second transistor has its first terminal connected to the inverting input terminal of the first operational amplifier and the second terminal of the fourth transistor; The third transistor has its control terminal connected to the first terminal of the compensation circuit and the second terminal of the fifth transistor, its two terminals are connected to the second terminal of the first resistor, and its first terminal is grounded. The fourth transistor has its control terminal connected to the second terminal of the compensation circuit and the second terminal of the sixth transistor, and its first terminal grounded. The fifth transistor has its control terminal connected to the control terminal of the sixth transistor, and both its control terminal and its first terminal are grounded. The sixth transistor has its first terminal grounded.

3. The bandgap reference circuit according to claim 2, characterized in that, The eleventh and twelfth transistors have the same width-to-length ratio of their conductive channels, and the formula for calculating the compensation current is as follows: Among them, I CTAT This represents the negative temperature coefficient compensation current, V. BE13 R1 represents the voltage between the control terminal and the second terminal of the thirteenth transistor, and R2 represents the resistance value of the second resistor.

4. The bandgap reference circuit according to claim 2, characterized in that, The bandgap reference voltage generation circuit includes: a fourteenth transistor, a third resistor, and a fifteenth transistor, wherein, The fourteenth transistor has its control terminal connected to the fifth terminal of the positive temperature coefficient current generating circuit, its first terminal connected to the first terminal of the third resistor, and its second terminal connected to the power supply. The third resistor has its second end connected to the second end of the fifteenth transistor, and its first end outputs a bandgap reference voltage. The fifteenth transistor has its control terminal connected to its first terminal and grounded.

5. The bandgap reference circuit according to claim 4, characterized in that, The first, second, seventh, eighth, ninth, tenth, and fourteenth transistors are P-type MOS transistors, the eleventh and twelfth transistors are N-type MOS transistors, and the third, fourth, fifth, sixth, thirteenth, and fifteenth transistors are bipolar transistors.

6. The bandgap reference circuit according to claim 4, characterized in that, The ratio of the width-to-length ratio of the seventh transistor's conductive channel to that of the eighth transistor's conductive channel is used to adjust the temperature coefficient of the bandgap reference voltage.

7. The bandgap reference circuit according to claim 6, characterized in that, The process of adjusting the temperature coefficient of the bandgap reference voltage includes: Calculate the relationship between bandgap reference voltage and temperature: in, This indicates the relationship between the bandgap reference voltage and temperature. This indicates the voltage-temperature relationship between the control terminal and the second terminal of the fifteenth transistor. This indicates the relationship between the voltage generated by a positive temperature coefficient current passing through a third resistor and the temperature. Adjust the ratio of the width-to-length ratio of the seventh transistor's conductive channel to that of the eighth transistor's conductive channel, so that... If the temperature coefficient of the bandgap reference voltage is 0, then the temperature coefficient of the bandgap reference voltage is 0.

Images