Low-noise LDO circuit

Abstract

The invention discloses a low-noise LDO (Low Dropout Regulator) circuit which comprises a band-gap reference circuit, reverse biased diodes in triodes are connected in series, the output reference voltage of the band-gap reference circuit is improved, a low-noise band-gap reference circuit structure capable of outputting high voltage is adopted, the amplification factor of reference voltage noise to an output end is reduced, and the output voltage is improved. And meanwhile, under the condition that a filter capacitor is not adopted, full-band low-noise output is realized.

Description

Technical Field

[0001] This application relates to the field of integrated circuit design, and particularly to a low-noise LDO circuit. Background Art

[0002] In contemporary electronic systems, the low dropout regulator (LDO), as a core component of the power management module, its output noise characteristics have increasingly attracted attention for their impact on system performance. With the continuous progress of integrated circuit technology, the system supply voltage continues to decrease while the function density increases significantly. Minute noise interference at the LDO output may be coupled to sensitive circuit modules through the power network, triggering chain reactions such as signal integrity degradation and measurement accuracy decline. Especially in application scenarios such as high-precision analog front-ends, radio frequency transceiver systems, and biomedical sensing, the noise level of the power rail is directly related to key indicators such as the signal-to-noise ratio and dynamic range of the system. For example, in the millimeter-wave radio frequency front-end of a 5G communication system, the high-frequency noise of the LDO may cause phase noise deterioration through local oscillator signal modulation; in an electroencephalogram signal acquisition system, the mixing of μV-level noise may result in the submergence of weak physiological signals. Existing research shows that the noise spectral characteristics of the LDO (including components such as thermal noise, flicker noise, and switching noise) will penetrate into the load circuit through the frequency-domain attenuation characteristics of the power supply rejection ratio (PSRR), and this noise transfer mechanism is particularly prominent in the design of mixed-signal SoCs.

[0003] To obtain an LDO with lower output noise, especially low-frequency noise, a filter with a lower cut-off frequency is usually required, and such a filter has a large area. For the power supply of extremely sensitive circuits (VCO power supply), an independent LDO circuit is often required for separate power supply, thus restricting the area of the LDO from being too large. Area, power consumption, and noise are mutually contradictory, and it is difficult to remove low-frequency noise in a fully integrated chip. Summary of the Invention

[0004] Aiming at the above deficiencies in the prior art, the present invention provides a low-noise LDO circuit, which solves the problem of the contradiction between the area, power consumption, and noise of traditional LDO circuits.

[0005] To achieve the above invention objective, the technical solution adopted by the present invention is: a low-noise LDO circuit, comprising: a bandgap reference circuit, which improves the output reference voltage of the bandgap reference circuit by connecting the reverse-biased diodes in the triode in series.

[0006] Further: it further includes an error amplifier, a super source follower, a power device, a feedback resistor R1, and a feedback resistor R2; The error amplifier is used to receive the output voltage of the low-noise LDO circuit and the reference voltage generated by the bandgap reference circuit, compare and amplify them, and obtain an error value; The super source follower is used to control the gate voltage of the power device according to the change of the error value; The power device is used to adjust the output current according to the gate voltage; The feedback resistors R1 and R2 together form a feedback network for sending the output voltage of the low-noise LDO circuit back to the error amplifier.

[0007] Further: The input end of the bandgap reference circuit is connected to the first input end of the power device. The input end of the bandgap reference circuit also serves as the input end of the low-noise LDO circuit. The output end of the bandgap reference circuit is connected to the positive input end of the error amplifier. The negative input end of the error amplifier is respectively connected to one end of the feedback resistor R1 and the grounded feedback resistor R2. The other end of the feedback resistor R1, which also serves as the output end of the low-noise LDO circuit, is connected to the output end of the power device. The output end of the error amplifier is connected to the input end of the super source follower. The output end of the super source follower is connected to the second input end of the power device.

[0008] Further: The bandgap reference circuit includes a field-effect transistor M1. The gate of the field-effect transistor M1 serves as the input end of the bandgap reference circuit. The drain of the field-effect transistor M1 is respectively connected to the source of the field-effect transistor M2 and the source of the field-effect transistor M3. The drain of the field-effect transistor M2 is respectively connected to the source of the field-effect transistor M7 and the drain of the field-effect transistor M9. The drain of the field-effect transistor M7 is respectively connected to the drain of the field-effect transistor M5, the gate of the field-effect transistor M10, the gate of the field-effect transistor M11, the gate of the field-effect transistor M12, and the gate of the field-effect transistor M13. The gate of the field-effect transistor M5 is respectively connected to the gate of the field-effect transistor M4, the drain of the field-effect transistor M4, and the drain of the field-effect transistor M6. The source of the field-effect transistor M6 is respectively connected to the drain of the field-effect transistor M3 and the drain of the field-effect transistor M8. The sources of the field-effect transistor M8 and the field-effect transistor M9 are both grounded. The gate of the field-effect transistor M6 is connected to the gate of the field-effect transistor M7. The gate of the field-effect transistor M8 is connected to the gate of the field-effect transistor M9. The sources of the field-effect transistor M1, the field-effect transistor M4, and the field-effect transistor M5 are all connected to the same power supply voltage; The source electrodes of field effect transistors M10, M11, M12, and M13 are all connected to an external power supply as the input terminals of the bandgap reference circuit. The drain electrode of field effect transistor M10 is connected to the emitter electrode of transistor Q3. The emitter electrode of transistor Q1 is respectively connected to the drain electrode of field effect transistor M11, the gate electrode of field effect transistor M2, and one end of resistor RD. The other end of resistor RD is connected to one end of resistor RE. The other end of resistor RE is connected to one end of resistor RF. The other end of resistor RF is respectively connected to the base electrode of transistor Q3, the collector electrode of transistor Q3, the collector electrode of transistor Q1, the collector electrode of transistor Q3, the collector electrode of transistor Q4, and one end of resistor RC. The emitter electrode of transistor Q2 is respectively connected to the gate electrode of field effect transistor M3, the drain electrode of field effect transistor M12, and one end of resistor RA. The other end of resistor RA is connected to one end of resistor RB. The other end of resistor RB is respectively connected to the other end of resistor RC and the base electrode of transistor Q4. The emitter electrode of transistor Q4 is respectively connected to the base electrode of transistor Q2 and the drain electrode of field effect transistor M13. The other end of resistor RA also serves as the output terminal of the bandgap reference circuit.

[0009] Furthermore: Field effect transistors M1 to M9 form a folded cascode amplifier, field effect transistors M10 to M13 form a current mirror, transistors Q1 to Q4 are used to provide negative temperature characteristics, resistor RC has a positive temperature coefficient, and resistors RA and RB have negative temperature coefficients.

[0010] Furthermore: The error amplifier is a folded cascode amplifier composed of field effect transistors.

[0011] The beneficial effects of the present invention are as follows: 1. By connecting the reverse-biased diodes in series in the transistor, the output reference voltage of the bandgap reference circuit is increased. 2. Based on the bandgap reference circuit structure with low noise that can output a relatively high voltage, the amplification factor of the reference voltage noise to the output terminal is reduced, enabling low-noise output across the entire frequency band without using a filter capacitor. Description of the Drawings

[0012] Figure 1 It is the bandgap reference circuit of the prior art solution.

[0013] Figure 2 It is a schematic diagram of a low-noise LDO circuit.

[0014] Figure 3 It is an example diagram of a low-noise LDO circuit. Detailed Embodiments

[0015] The following describes the specific embodiments of the present invention to facilitate those skilled in the art of this technology to understand the present invention. However, it should be clear that the present invention is not limited to the scope of the specific embodiments. For those of ordinary skill in the art of this technology, as long as various changes are within the spirit and scope of the present invention defined and determined by the appended claims, these changes are obvious, and all inventions and creations using the concept of the present invention are within the scope of protection.

[0016] As Figure 1 shown, it is a bandgap reference circuit of the prior art solution, where the voltage across the resistor RC has a positive temperature characteristic, and the voltage difference V between the base and emitter of the triode has a negative temperature characteristic. By adjusting the magnitude of the resistance value, a voltage with zero temperature coefficient can be obtained. The output voltage V of the bandgap reference circuit is given by the weighted sum of the base voltage of the triode and V, so the amplification of the noise of the amplifier is almost zero. BE The output voltage V of the prior art is differentiated with respect to temperature T, and the formula is: REF where β is the amplification factor of the base current I of the triode and the collector current I; N is the ratio of the number of triodes Q1 to the number of triodes Q2 in; VT = (kT) / q, VT is the thermal voltage, and its physical meaning represents the characteristic voltage of a semiconductor device in thermal equilibrium and is directly related to temperature; V represents the voltage difference between the base and emitter of the triode Q1, k is the Boltzmann constant, and q is the elementary charge. BE At room temperature, the negative temperature coefficient of V is -1.5 mV / K, and the temperature coefficient of VT is +0.087 mV / k. Assuming N is equal to 24 and ignoring the resistance ratio of the first term in the formula, in order to obtain a voltage with zero temperature coefficient, it is deduced that RB / (RA + RB) is approximately equal to 0.185. The reverse bias voltage of the base-emitter of a general triode is 750 mV. Substituting into the formula, the output voltage V is only about 220 mV. If the reference level V in the LDO is lower, the feedback coefficient is smaller, which leads to an increase in the amplification factor of the noise, and the output noise of the LDO will also increase accordingly. Therefore, the bandgap reference circuit of the prior art can only output a low-noise voltage V with a relatively small reference voltage. When the output voltage is fixed, the feedback coefficient becomes smaller, and the amplification factor of the noise of the reference voltage to the output terminal becomes larger, which is not beneficial to the total output noise of the LDO.

[0017] The output voltage V of the prior art REF The formula for differentiating with respect to temperature T is: where β is the amplification factor of the base current I of the triode and the collector current I; N is the ratio of the number of triodes Q1 to the number of triodes Q2 in; VT = (kT) / q, VT is the thermal voltage, and its physical meaning represents the characteristic voltage of a semiconductor device in thermal equilibrium and is directly related to temperature; V represents the voltage difference between the base and emitter of the triode Q1, k is the Boltzmann constant, and q is the elementary charge. b and the collector current I c ; N is Figure 1 the ratio of the number of triodes Q1 to the number of triodes Q2 in; VT = (kT) / q, VT is the thermal voltage, and its physical meaning represents the characteristic voltage of a semiconductor device in thermal equilibrium and is directly related to temperature; V represents the voltage difference between the base and emitter of the triode Q1, k is the Boltzmann constant, and q is the elementary charge. BE1 represents the voltage difference between the base and emitter of the triode Q1, k is the Boltzmann constant, and q is the elementary charge.

[0018] At room temperature, the negative temperature coefficient of V is -1.5 mV / K, and the temperature coefficient of VT is +0.087 mV / k. Assuming N is equal to 24 and ignoring the resistance ratio of the first term in the formula, in order to obtain a voltage with zero temperature coefficient, it is deduced that RB / (RA + RB) is approximately equal to 0.185. The reverse bias voltage of the base-emitter of a general triode is 750 mV. Substituting into the formula, the output voltage V is only about 220 mV. If the reference level V in the LDO is lower, the feedback coefficient is smaller, which leads to an increase in the amplification factor of the noise, and the output noise of the LDO will also increase accordingly. Therefore, the bandgap reference circuit of the prior art can only output a low-noise voltage V with a relatively small reference voltage. When the output voltage is fixed, the feedback coefficient becomes smaller, and the amplification factor of the noise of the reference voltage to the output terminal becomes larger, which is not beneficial to the total output noise of the LDO. BE ; N is BE The reverse bias voltage is 750 mV. Substituting into the formula, the output voltage V can be obtained as only about 220 mV. If the reference level V in the LDO is lower, the feedback coefficient is smaller, which leads to an increase in the amplification factor of the noise, and the output noise of the LDO will also increase accordingly. Therefore, the bandgap reference circuit of the prior art can only output a low-noise voltage V with a relatively small reference voltage. When the output voltage is fixed, the feedback coefficient becomes smaller, and the amplification factor of the noise of the reference voltage to the output terminal becomes larger, which is not beneficial to the total output noise of the LDO. REF is only about 220 mV. If the reference level V in the LDO is lower, the feedback coefficient is smaller, which leads to an increase in the amplification factor of the noise, and the output noise of the LDO will also increase accordingly. Therefore, the bandgap reference circuit of the prior art can only output a low-noise voltage V with a relatively small reference voltage. When the output voltage is fixed, the feedback coefficient becomes smaller, and the amplification factor of the noise of the reference voltage to the output terminal becomes larger, which is not beneficial to the total output noise of the LDO. REF is lower, the feedback coefficient is smaller, which leads to an increase in the amplification factor of the noise, and the output noise of the LDO will also increase accordingly. Therefore, the bandgap reference circuit of the prior art can only output a low-noise voltage V with a relatively small reference voltage. When the output voltage is fixed, the feedback coefficient becomes smaller, and the amplification factor of the noise of the reference voltage to the output terminal becomes larger, which is not beneficial to the total output noise of the LDO. REF When the output voltage is fixed, the feedback coefficient becomes smaller, and the amplification factor of the noise of the reference voltage to the output terminal becomes larger, which is not beneficial to the total output noise of the LDO.

[0019] In traditional designs, a low-pass filter circuit needs to be added at the output end of the bandgap reference circuit to reduce the noise output. However, the low-pass filter itself will also introduce noise. To achieve low-noise output across the entire frequency band, a low-pass filter with an extremely low cut-off frequency is required, and the area of the filter capacitor will be extremely large.

[0020] To address the above deficiencies, the present application provides a low-noise LDO circuit, including: a bandgap reference circuit, which improves the output reference voltage of the bandgap reference circuit by connecting the reverse-biased diodes in the triode in series.

[0021] As Figure 2 shown, the low-noise LDO circuit provided by the present application further includes an error amplifier, a super source follower, a power device, a feedback resistor R1, and a feedback resistor R2; The error amplifier is used to receive the output voltage of the low-noise LDO circuit and the reference voltage generated by the bandgap reference circuit, compare and amplify them, and obtain an error value; The super source follower is used to control the gate voltage of the power device according to the change of the error value; The power device is used to adjust the output current according to the gate voltage; The feedback resistor R1 and the feedback resistor R2 together form a feedback network, which is used to send the output voltage of the low-noise LDO circuit back to the error amplifier.

[0022] Specifically, the input end of the bandgap reference circuit is connected to the first input end of the power device. The input end of the bandgap reference circuit also serves as the input end of the low-noise LDO circuit. The output end of the bandgap reference circuit is connected to the positive input end of the error amplifier. The negative input end of the error amplifier is respectively connected to one end of the feedback resistor R1 and the grounded feedback resistor R2. The other end of the feedback resistor R1 serves as the output end of the low-noise LDO circuit and is also connected to the output end of the power device. The output end of the error amplifier is connected to the input end of the super source follower. The output end of the super source follower is connected to the second input end of the power device.

[0023] To obtain a lower output noise across the entire frequency band, the noise of the bandgap reference circuit needs to be very low and the proportion of the noise of the bandgap reference circuit in the output noise should be small. The output reference voltage V REF is the weighted sum and superposition of the triode base and V BE to achieve zero temperature coefficient. At the same time, the noise of the amplifier reaches V REFThe magnification factor is almost zero, thus achieving low noise; moreover, since the noise output by the bandgap reference circuit is very small, a low-pass filter is not required, greatly reducing the circuit area. Since the output voltage of the bandgap reference circuit is higher than that of the existing low-noise technology, when the output voltage is fixed, the feedback coefficient increases, and the magnification factor of the noise of the reference voltage to the output terminal becomes smaller. The output noise of the bandgap reference circuit accounts for a smaller proportion of the total noise of the LDO, thereby achieving a reduction in the output noise.

[0024] As Figure 3 shown, in an embodiment of the present invention, the bandgap reference circuit includes a field-effect transistor M1. The gate of the field-effect transistor M1 serves as the input terminal of the bandgap reference circuit. The drain of the field-effect transistor M1 is respectively connected to the source of the field-effect transistor M2 and the source of the field-effect transistor M3. The drain of the field-effect transistor M2 is respectively connected to the source of the field-effect transistor M7 and the drain of the field-effect transistor M9. The drain of the field-effect transistor M7 is respectively connected to the drain of the field-effect transistor M5, the gate of the field-effect transistor M10, the gate of the field-effect transistor M11, the gate of the field-effect transistor M12, and the gate of the field-effect transistor M13. The gate of the field-effect transistor M5 is respectively connected to the gate of the field-effect transistor M4, the drain of the field-effect transistor M4, and the drain of the field-effect transistor M6. The source of the field-effect transistor M6 is respectively connected to the drain of the field-effect transistor M3 and the drain of the field-effect transistor M8. The sources of the field-effect transistor M8 and the field-effect transistor M9 are both grounded. The gate of the field-effect transistor M6 is connected to the gate of the field-effect transistor M7. The gate of the field-effect transistor M8 is connected to the gate of the field-effect transistor M9; the sources of the field-effect transistor M1, the field-effect transistor M4, and the field-effect transistor M5 are all connected to the same power supply voltage; the sources of the field-effect transistor M10, the field-effect transistor M11, the field-effect transistor M12, and the field-effect transistor M13 all serve as the input terminals of the bandgap reference circuit and are connected to an external power supply. The drain of the field-effect transistor M10 is connected to the emitter of the triode Q3. The emitter of the triode Q1 is respectively connected to the drain of the field-effect transistor M11, the gate of the field-effect transistor M2, and one end of the resistor RD. The other end of the resistor RD is connected to one end of the resistor RE. The other end of the resistor RE is connected to one end of the resistor RF. The other end of the resistor RF is respectively connected to the base of the triode Q3, the collector of the triode Q3, the collector of the triode Q1, the collector of the triode Q3, the collector of the triode Q4, and one end of the resistor RC. The emitter of the triode Q2 is respectively connected to the gate of the field-effect transistor M3, the drain of the field-effect transistor M12, and one end of the resistor RA. The other end of the resistor RA is connected to one end of the resistor RB. The other end of the resistor RB is respectively connected to the other end of the resistor RC and the base of the triode Q4. The emitter of the triode Q4 is respectively connected to the base of the triode Q2 and the drain of the field-effect transistor M13. The other end of the resistor RA also serves as the output terminal of the bandgap reference circuit.

[0025] Specifically, field effect transistors M1 to M9 form a folded cascode amplifier, field effect transistors M10 to M13 form a current mirror, transistors Q1 to Q4 are used to provide negative temperature characteristics, resistor RC has a positive temperature coefficient, and resistors RA and RB have negative temperature coefficients.

[0026] Specifically, the error amplifier is a folded cascode amplifier composed of field effect transistors. In this embodiment, the error amplifier includes field effect transistor M15. The gate of field effect transistor M15 is connected to the other end of resistor RA. The emitter of field effect transistor M15 is respectively connected to the emitter of field effect transistor M16 and the drain of field effect transistor M14. The drain of field effect transistor M15 is respectively connected to the emitter of field effect transistor M22 and the drain of field effect transistor M24. The gate of field effect transistor M16 serves as the negative input terminal of the error amplifier. The drain of field effect transistor M16 is respectively connected to the emitter of field effect transistor M21 and the drain of field effect transistor M23. The drain of field effect transistor M21 is respectively connected to the drain of field effect transistor M19, the gate of field effect transistor M17, and the gate of field effect transistor M18. The emitter of field effect transistor M19 is connected to the drain of field effect transistor M17. The drain of field effect transistor M22 is connected to the drain of field effect transistor M20. The source of field effect transistor M20 is connected to the drain of field effect transistor M18. The gate of field effect transistor M20 is connected to the gate of field effect transistor M19. The gate of field effect transistor M21 is connected to the gate of field effect transistor M22. The gate of field effect transistor M23 is connected to the gate of field effect transistor M24. The drain of field effect transistor M22 also serves as the output terminal of the error amplifier.

[0027] Preferably, as Figure 3 shown, the source of field effect transistor M14, the source of field effect transistor M17, and the source of field effect transistor M18 can also be connected to the source of field effect transistor M13, that is, the error amplifier and the bandgap reference circuit use the same external power supply input.

[0028] In this embodiment, the super source follower (SSF, Super Source Follower) includes field effect transistor M26. The gate of field effect transistor M26 serves as the input terminal of the super source follower and is connected to the output terminal of the error amplifier (i.e., the drain of field effect transistor M22). The drain of field effect transistor M26 is respectively connected to the emitter of field effect transistor M25 and the drain of field effect transistor M28. The emitter of field effect transistor M26 is respectively connected to the drain of field effect transistor M27 and the gate of field effect transistor M28. The drain of field effect transistor M28 also serves as the output terminal of the super source follower and is connected to the power device.

[0029] In this embodiment, a field-effect transistor M29 is used to be equivalent to a power device. The gate of the field-effect transistor M29 serves as the second input terminal of the power device and is connected to the drain of the field-effect transistor M28. The drain of the field-effect transistor M29 serves as the first input terminal of the rate device and is connected to the source of the field-effect transistor M13. The source of the field-effect transistor M29 serves as the output terminal of the power device.

[0030] Optionally, the output terminal of the low-noise LDO circuit can be connected to an error amplifier. As in this embodiment, the other end of the feedback resistor R1 serves as the output terminal of the low-noise LDO circuit and is also connected to one end of the capacitor C1. The other end of the capacitor C1 is connected to the drain of the field-effect transistor M24.

[0031] The beneficial effect of connecting the output terminal of the low-noise LDO circuit to the drain of the field-effect transistor M24 through the capacitor C1 is as follows: Using the cascode compensation technique, the output pole is pushed to a higher frequency, making the entire circuit stable and preventing the problem of output oscillation. This cascode compensation has no feedforward path theoretically compared with the traditional Miller compensation.

[0032] In summary, without using a large-area low-pass filter, the present invention adopts a high-output reference voltage and a low-noise bandgap reference circuit, and finally realizes the reduction of the output noise of the LDO in the full frequency band. It greatly alleviates the contradiction between area and noise, and realizes a fully integrated full-band low-noise LDO.

[0033] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A low noise LDO circuit, characterized in that: include: The bandgap reference circuit improves the output reference voltage of the bandgap reference circuit by connecting the reverse biased diode in series in the triode.

2. The low noise LDO circuit according to claim 1, characterized in that: It also includes an error amplifier, a super source follower, a power device, a feedback resistor R1 and a feedback resistor R2; The error amplifier is used to receive the output voltage of the low-noise LDO circuit and the reference voltage generated by the bandgap reference circuit, and compare and amplify them to obtain an error value; The super source follower is used to control the gate voltage of the power device according to the change of the error value; The power device is used to regulate the output current according to the gate voltage; Feedback resistor R1 and feedback resistor R2 together form a feedback network for sending the output voltage of the low noise LDO circuit back to the error amplifier.

3. The low noise LDO circuit according to claim 2, characterized in that: The input end of the bandgap reference circuit is connected to the first input end of the power device, the input end of the bandgap reference circuit also serves as the input end of the low-noise LDO circuit, the output end of the bandgap reference circuit is connected to the positive input end of the error amplifier, the negative input end of the error amplifier is respectively connected to one end of the feedback resistor R1 and the grounded feedback resistor R2, the other end of the feedback resistor R1 is also connected to the output end of the power device as the output end of the low-noise LDO circuit, the output end of the error amplifier is connected to the input end of the super source follower, and the output end of the super source follower is connected to the second input end of the power device.

4. The low noise LDO circuit according to claim 3, characterized in that: The bandgap reference circuit includes a field effect tube M1, the gate of the field effect tube M1 is used as the input end of the bandgap reference circuit, the drain of the field effect tube M1 is respectively connected to the source of the field effect tube M2 and the source of the field effect tube M3, the drain of the field effect tube M2 is respectively connected to the source of the field effect tube M7 and the drain of the field effect tube M9, the drain of the field effect tube M7 is respectively connected to the drain of the field effect tube M5, the gate of the field effect tube M10, the gate of the field effect tube M11, the gate of the field effect tube M12 and the gate of the field effect tube M13, and the field effect tube M5 is respectively connected to the gate of the field effect tube M10. The gate of the field effect transistor M1 is connected to the gate of the field effect transistor M4, the drain of the field effect transistor M4 and the drain of the field effect transistor M6 respectively, the source of the field effect transistor M6 is connected to the drain of the field effect transistor M3 and the drain of the field effect transistor M8 respectively, the source of the field effect transistor M8 and the source of the field effect transistor M9 are both grounded, the gate of the field effect transistor M6 is connected to the gate of the field effect transistor M7, and the gate of the field effect transistor M8 is connected to the gate of the field effect transistor M9; the source of the field effect transistor M1, the source of the field effect transistor M4 and the source of the field effect transistor M5 are all connected to the same power supply voltage; The source of the field effect transistor M10, the source of the field effect transistor M11, the source of the field effect transistor M12 and the source of the field effect transistor M13 are all connected to the external power supply as the input end of the bandgap reference circuit, the drain of the field effect transistor M10 is connected to the emitter of the transistor Q3, the emitter of the transistor Q1 is respectively connected to the drain of the field effect transistor M11, the gate of the field effect transistor M2 and one end of the resistor RD, the other end of the resistor RD is connected to one end of the resistor RE, the other end of the resistor RE is connected to one end of the resistor RF, the other end of the resistor RF is respectively connected to the base of the transistor Q3, the transistor Q The collector of transistor Q3, the collector of transistor Q1, the collector of transistor Q3, the collector of transistor Q4 and one end of resistor RC are connected, the emitter of transistor Q2 is connected to the gate of field effect transistor M3, the drain of field effect transistor M12 and one end of resistor RA respectively, the other end of resistor RA is connected to one end of resistor RB, the other end of resistor RB is connected to the other end of resistor RC and the base of transistor Q4 respectively, the emitter of transistor Q4 is connected to the base of transistor Q2 and the drain of field effect transistor M13 respectively, and the other end of resistor RA also serves as the output end of the bandgap reference circuit.

5. The low noise LDO circuit according to claim 4, characterized in that: Field effect transistors M1 to M9 form a folded common source and common gate amplifier, field effect transistors M10 to M13 form a current mirror, transistors Q1 to Q4 are used to provide negative temperature characteristics, the voltage drop across resistor RC is a positive temperature coefficient, and the voltage drop across resistors RA and RB is a negative temperature coefficient.

6. The low noise LDO circuit according to claim 2, characterized in that: The error amplifier is a folded common-source common-gate amplifier composed of field-effect transistors.

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