Fast transient response LDO circuit without off-chip capacitor

Abstract

The invention discloses a fast transient response LDO circuit without an off-chip capacitor, and relates to the technical field of LDOs. Comprising an error amplification circuit, a class AB super source following circuit and an active capacitor. The class AB super source following circuit is arranged between the error amplifying circuit and the output stage; the class AB super source follower circuit is arranged between the error amplification circuit and the output stage, and the output stage provides working current for a load; the class AB super source follower circuit can improve the slew rate of the grid electrode of the output power tube and enhance the transient response speed; meanwhile, the class AB super source follower circuit at least comprises a transient response enhancement module which is used for providing a path for directly adjusting the output voltage and further enhancing the transient response speed. The active capacitor is extremely low in power consumption in a static state; and in a transient state, a transient large current can be provided to reduce output overshoot, so that the output voltage is fast and stable. According to the LDO, the active capacitor technology, the high-pass filtering technology and the class AB super source follower are adopted to achieve fast transient response, and the monolithic integrated transient enhanced LDO is achieved.

Description

Technical Field

[0001] The invention relates to the field of LDO technology, and in particular to a fast transient response LDO circuit without an off-chip capacitor. Background Art

[0002] LDO is widely used in various types of electronic devices because of its smaller size, higher integration, fewer peripheral devices and lower cost. Traditional LDO needs to place a microfarad output filter capacitor at the output. This large-capacitance output filter capacitor cannot be integrated on the chip and can only be added to the PCB board. This not only occupies the chip pad area, but also introduces parasitic inductance and resistance in the connecting wire, and also increases the cost. Therefore, the research and development of on-chip integrated LDO is of research significance.

[0003] For monolithic integrated LDO, there is no component for storing and discharging transient charge because there is no output filter capacitor. Without additional transient enhancement design, the overshoot / undershoot is large and the recovery time is long, resulting in a large output voltage during the transient period, which may cause device damage and circuit performance degradation. Therefore, achieving fast transient response is an important goal in the design of LDO without external capacitors.

[0004] Therefore, there is an urgent need to provide a more reliable fast transient response LDO circuit without external capacitors. Summary of the invention

[0005] The object of the present invention is to provide a fast transient response LDO circuit without external capacitors, which is used to achieve full on-chip integration in the form of no external capacitors to reduce cost and area.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] The present invention provides a fast transient response LDO circuit without an off-chip capacitor, comprising:

[0008] Error amplifier circuit, class AB super source follower circuit and active capacitor;

[0009] The class AB super source follower circuit is arranged between the error amplifier circuit and the output stage;

[0010] The class AB super source-follower circuit at least includes a transient response enhancement module; the transient response enhancement module is used to provide a path for adjusting the power tube current and accelerate the transient response;

[0011] The output stage provides operating current to the load.

[0012] Optionally, the error amplification circuit includes a first bandwidth extension unit, a second bandwidth extension unit and a gain enhancement unit; the gain enhancement unit is connected between the first bandwidth extension unit and the second bandwidth extension unit;

[0013] The error amplifier circuit is used to adjust the output voltage; the feedback voltage measured by the sampling circuit at the negative end of the error amplifier circuit becomes smaller, and the reference voltage source measured at the positive end of the error amplifier circuit remains unchanged; the error amplifier circuit outputs a positive difference voltage based on the detected voltage difference, so that the current flowing through the power tube increases and the voltage at the load end increases.

[0014] Optionally, the class AB super source circuit further includes:

[0015] A super source follower structure; the super source follower structure is connected to the transient response enhancement module;

[0016] The transient response enhancement module at least includes a first resistor and a first capacitor; the super source follower structure at least includes a first transistor, a second transistor, a third transistor and an eighth transistor.

[0017] Optionally, when the load changes suddenly, the output voltage changes and is coupled to the gate of the first transistor through the first capacitor. The gate of the power tube is regulated by the first transistor and the second transistor to provide transient source current or transient sink current to achieve transient enhancement.

[0018] Optionally, the output voltage is coupled to the drain terminal of the first transistor and then coupled to the gate of the third transistor through a second capacitor, so that the gate of the power transistor is regulated from the drain terminal of the third transistor.

[0019] Optionally, the class AB super source realizes class AB output along with the second transistor, the second resistor and the second capacitor in the circuit;

[0020] The first transistor, the second transistor, the third transistor, the eighth transistor, the second resistor and the second capacitor in the class AB super source follower circuit realize a super source follower structure. When the output increases or decreases, the gate of the power tube responds to the output voltage change.

[0021] Optionally, in the class AB super source follower circuit, when the output voltage increases, the gate of the eighth transistor increases, the source of the eighth transistor increases, and the output of the power tube becomes lower, thereby realizing negative feedback regulation;

[0022] When the output voltage becomes smaller, the gate of the eighth transistor decreases, the source of the eighth transistor decreases, and the output of the power tube becomes higher, thereby realizing negative feedback regulation.

[0023] Optionally, the active capacitor comprises at least:

[0024] a fourth transistor, a fifth transistor, a sixth transistor, and a seventh transistor;

[0025] The active capacitor provides a transient large current to the circuit when the load changes suddenly;

[0026] When the output voltage decreases, the gate voltage of the sixth transistor decreases, and the current flowing through the sixth transistor increases;

[0027] When the output voltage increases, the gate voltage of the seventh transistor increases, and the current flowing through the seventh transistor increases.

[0028] Optionally, when the output voltage suddenly changes, the fourth transistor and the fifth transistor amplify the error, and the output voltage is directly adjusted to a stable value through the sixth transistor and the seventh transistor.

[0029] Compared with the prior art, the present invention provides a fast transient response LDO circuit without external capacitors. It includes an error amplifier circuit, a classAB super source follower circuit and an active capacitor; and the classAB super source follower circuit is arranged between the error amplifier circuit and the output stage, and the output stage provides working current for the load; the classAB super source follower circuit can improve the gate slew rate of the output power tube and enhance the transient response speed; at the same time, the classAB super source follower circuit includes at least a transient response enhancement module, which is used to provide a path for directly adjusting the output voltage, further enhancing the transient response speed. The active capacitor has extremely low power consumption in static state; in transient state, it can provide a transient large current to reduce output overshoot and make the output voltage quickly stabilized. The circuit structure provided by the present invention adopts active capacitor technology, high-pass filtering technology and classAB super source follower to achieve fast transient response, and realizes a monolithic integrated transient enhanced LDO. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0031] Figure 1 It is a schematic diagram of the structure of an over-temperature protection circuit based on a voltage comparator in the prior art;

[0032] Figure 2 A schematic diagram of a fast transient response LDO circuit without external capacitors provided by the present invention;

[0033] FIG3( a ) is a diagram showing simulation results of a transient enhanced LDO provided by the present invention when the load current suddenly changes from 0 mA to 100 mA;

[0034] FIG3( b ) is a diagram showing simulation results of a transient enhanced LDO provided by the present invention when the load current suddenly changes from 100 mA to 0 mA.

[0035] Reference numerals:

[0036] 1-error amplifier circuit, 2-class AB super source follower circuit, 3-active capacitor, 11-first bandwidth extension unit, 13-second bandwidth extension unit, 12-gain enhancement unit, 21-transient response enhancement module. DETAILED DESCRIPTION

[0037] In order to clearly describe the technical solutions of the embodiments of the present invention, in the embodiments of the present invention, words such as "first" and "second" are used to distinguish the same items or similar items with basically the same functions and effects. For example, the first threshold and the second threshold are only used to distinguish different thresholds, and their order is not limited. Those skilled in the art can understand that words such as "first" and "second" do not limit the quantity and execution order, and words such as "first" and "second" do not necessarily limit them to be different.

[0038] It should be noted that, in the present invention, words such as "exemplary" or "for example" are used to indicate examples, illustrations or descriptions. Any embodiment or design described as "exemplary" or "for example" in the present invention should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of words such as "exemplary" or "for example" is intended to present related concepts in a specific way.

[0039] In the present invention, "at least one" means one or more, and "plurality" means two or more. "And / or" describes the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone, where A and B can be singular or plural. The character " / " generally indicates that the associated objects before and after are in an "or" relationship. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single or plural items. For example, at least one of a, b or c can mean: a, b, c, the combination of a and b, the combination of a and c, the combination of b and c, or the combination of a, b and c, where a, b, c can be single or multiple.

[0040] First, some abbreviations, English and key term definitions used in the embodiments of this specification are explained:

[0041] MOS tube (metal-oxide-semiconductor field-effect transistor);

[0042] BJT tube (bipolar junction transistor);

[0043] LDO (low dropout linear regulator);

[0044] Active current technology (AC) active capacitor technology;

[0045] Supersourcefollower (SSF) Super source follower.

[0046] At present, the traditional architecture LDO circuit is Figure 1 As shown. The LDO structure in the prior art includes a reference voltage module, an error amplifier circuit, a power tube and a feedback network. When the output voltage changes, this change will be captured by the feedback resistor. The error amplifier circuit compares the reference voltage source with the output voltage (VOUT) obtained by the feedback resistor voltage divider and amplifies the error to generate a control signal to control the conduction degree of the adjustment tube, thereby controlling the output voltage to achieve constant output voltage. The adjustment tube is affected by the error amplifier circuit to restore it to the set voltage level and maintain output stability. However, this structure cannot be integrated on a single chip, and the output filter capacitor can only be added to the PCB board. This not only occupies the chip pad area, but also introduces parasitic inductance and resistance in the connecting wire, and also increases the cost.

[0047] In order to solve the defects in the prior art, the present invention provides a fast transient response LDO circuit without external capacitors. Next, the solution provided in the embodiment of this specification is described in conjunction with the accompanying drawings:

[0048] like Figure 2 As shown, the present invention provides a fast transient response LDO circuit without off-chip capacitors, which may include the following structure:

[0049] Error amplifier circuit 1, class AB super source follower circuit 2 and active capacitor 3;

[0050] The class AB super source-follower circuit 2 is arranged between the error amplifier circuit 1 and the active capacitor 3;

[0051] The class AB super source-follower circuit 2 at least includes a transient response enhancement module 21; the transient response enhancement module 21 is used to provide a path for regulating the power tube current and accelerate the transient response.

[0052] In the above structure, a low dropout regulator (LDO) is a commonly used power management circuit, which is used to reduce the DC power supply voltage to a stable DC voltage to supply power to a load.

[0053] The error amplifier circuit 1 is used to amplify the error between the actual measured value and the expected value, so as to drive the subsequent circuit or system to compensate or adjust the error.

[0054] Source Follower is a common amplifier circuit, also known as voltage follower or common emitter follower. Its characteristic is that the output follows the input voltage (that is, the source voltage).

[0055] Super source follower (SSF) improves the performance of the traditional source follower by adding an extra transistor and a current source, significantly reducing the output resistance of the source follower from a larger value to a smaller value.

[0056] Active Capacitors3: New electronic components that combine the functions of traditional capacitors and active electronic components (such as operational amplifiers). They are mainly used to improve the performance of circuits, especially in applications that require high precision, low noise and high stability, by enhancing or adjusting the characteristics of capacitors through active components.

[0057] The class AB super source-follower circuit 2 is provided with a transient response enhancement module 21 for providing a path for adjusting the power tube current and accelerating the transient response.

[0058] Figure 2 The circuit in the invention comprises an error amplifier circuit 1, a classAB super source follower circuit 2 and an active capacitor 3; and the classAB super source follower circuit 2 is arranged between the error amplifier circuit 1 and the active capacitor 3; the classAB super source follower circuit 2 is arranged between the error amplifier circuit 1 and the output stage, and the output stage provides working current for the load; the classAB super source follower circuit 2 can improve the gate slew rate of the output power tube and enhance the transient response speed; at the same time, the classAB super source follower circuit 2 at least includes a transient response enhancement module 21, which is used to provide a path for directly adjusting the output voltage, and further enhance the transient response speed. The active capacitor has extremely low power consumption in static state; in transient state, it can provide a transient large current to reduce output overshoot and make the output voltage quickly stabilized. The circuit structure provided by the present invention adopts active capacitor 3 technology, high-pass filtering technology and classAB super source follower to achieve fast transient response, and realizes a monolithic integrated transient enhanced LDO.

[0059] based on Figure 2 The embodiment of this specification also provides some specific structures of the circuit, which will be described below.

[0060] First, if Figure 2 As shown, for the error amplifier circuit, the error amplifier circuit 1 may include a first bandwidth extension unit 11, a second bandwidth extension unit 13 and a gain enhancement unit 12; the gain enhancement unit 12 is connected between the first bandwidth extension unit 11 and the second bandwidth extension unit 13;

[0061] The error amplifier circuit is used to adjust the output voltage; the feedback voltage measured by the sampling circuit at the negative end of the error amplifier circuit becomes smaller, and the reference voltage source measured at the positive end of the error amplifier circuit remains unchanged; the error amplifier circuit outputs a positive difference voltage based on the detected voltage difference, so that the current flowing through the power tube increases and the voltage at the load end increases.

[0062] The basic voltage regulation principle and technical effect corresponding to the setting of the above error amplifier circuit are:

[0063] When the output voltage decreases due to changes in the load, the feedback voltage measured by the sampling circuit at the negative end of the error amplifier circuit decreases, while the reference voltage source measured at the positive end of the error amplifier circuit remains unchanged. The error amplifier circuit detects the voltage difference between the two and outputs a positive difference voltage, which increases the current flowing through the power tube, thereby increasing the voltage at the load end, achieving the purpose of regulating the output voltage.

[0064] For the class AB class super source follower circuit 2, the class AB class super source follower circuit 2 may include a transient response enhancement module 21 and a super source follower structure. The transient response enhancement module 21 may include at least a first resistor and a first capacitor; and the super source follower structure may include at least a first transistor, a second transistor, a third transistor, and an eighth transistor.

[0065] Specifically, the classAB super source implements the classAB output with the second transistor, the second resistor and the second capacitor in the circuit 2;

[0066] The first transistor, the second transistor, the third transistor, the eighth transistor, the second resistor and the second capacitor in the class AB super source follower circuit 2 realize a super source follower structure. When the output increases or decreases, the gate of the power tube responds to the output voltage change.

[0067] When the output voltage increases, the gate of the eighth transistor increases, the source of the eighth transistor increases, and the output of the power tube becomes lower, thereby realizing negative feedback regulation;

[0068] When the output voltage becomes smaller, the gate of the eighth transistor decreases, the source of the eighth transistor decreases, and the output of the power tube becomes higher, thereby realizing negative feedback regulation.

[0069] The transient enhancement principle of the class AB super source follower in the above structure and the corresponding technical effects are:

[0070] First, the realization of class AB super source follower and the principle of reducing overshoot / undershoot. One of the purposes of adding a source follower between the error amplifier circuit and the power tube is to solve the stability problem caused by two low-frequency poles under light load. In order to achieve high precision of LDO, the error amplifier circuit needs high gain and high output impedance; in order to achieve strong driving capability, a large-sized power tube is required, so the pole frequency at the output end of the error amplifier circuit is very low.

[0071] At the same time, when the load is light, the impedance of the LDO output is large and the pole frequency is low. Two low-frequency poles will cause stability problems. After adding the source follower, its small input gate impedance pushes the pole at EA to high frequency; its small output impedance also pushes the pole at the power tube gate to high frequency. Therefore, at low frequency, there is only one main pole at the LDO output, and the entire loop is stable.

[0072] When the load changes suddenly, the VOUT change is coupled to the gate of M1 through C1, and the gate of the power tube is regulated through M1 and M2 to provide transient pull / sink current. A transient enhancement effect is achieved. Secondly, VOUT is coupled to the drain of M1 and then coupled to the gate of M3 through C2, and the gate of the power tube is regulated from the drain of M3. The two are superimposed to achieve class AB output.

[0073] For the class AB super source follower circuit, more specifically, when the output VOUT increases, VFB increases, the gate of M8 increases, the source of M8 increases, the output of the power tube becomes low, and negative feedback regulation is achieved.

[0074] At the same time, the increase in the gate voltage of M8 will also cause M2 to generate a pull-down current to lower the output of the power tube and increase the positive gate slew rate. When the output VOUT becomes smaller, VFB decreases, the gate voltage of M8 decreases, the source voltage of M8 decreases, and the output of the power tube increases, thus achieving negative feedback regulation.

[0075] At the same time, the reduction of M8 gate voltage will also increase its drain voltage, which is coupled to the gate of M3 through capacitor C2. M3 provides a fast and large pull-up current to increase the gate negative voltage slew rate. M1-M3 and M8 form an SSF structure. M2, R2 and C2 realize classAB output. M1-M3, M8, R2 and C2 realize classAB SSF, so that when the output increases or decreases, the power tube gate can quickly respond to VOUT changes. ClassAB output accelerates the transient response process.

[0076] For the active capacitor 3, the active capacitor 3 may at least include: a fourth transistor, a fifth transistor, a sixth transistor and a seventh transistor;

[0077] The active capacitor 3 provides a transient large current to the circuit when the load changes suddenly;

[0078] When the output voltage decreases, the gate voltage of the sixth transistor decreases, and the current flowing through the sixth transistor increases;

[0079] When the output voltage increases, the gate voltage of the seventh transistor increases, and the current flowing through the seventh transistor increases;

[0080] When the output voltage suddenly changes, the fourth transistor and the fifth transistor amplify the error, and directly adjust the output voltage to be stable through the sixth transistor and the seventh transistor.

[0081] For the above active capacitor 3, the technical transient enhancement principle and technical effect of the active capacitor 3 based on the current comparator are as follows:

[0082] When VOUT changes suddenly, M4 and M5 amplify the error, and directly adjust VOUT through M6 and M7 to stabilize the output, achieving a transient enhancement effect.

[0083] More specifically, the function of the active capacitor 3 is to provide a transient large current to the circuit when the load changes suddenly. The active capacitor 3 has a circuit that provides a transient pull-up current and a transient pull-down current. Specifically, when providing a transient pull-up current, when VOUT decreases, the gate voltage of M6 decreases, and the current flowing through M6 increases, causing VOUT to increase.

[0084] It can also provide transient pull-down current. When VOUT increases, the gate voltage of M7 increases, and the current flowing through M7 increases, causing VOUT to decrease.

[0085] For Transient enhanced (transient response enhancement module 21) in the class AB super source follower circuit: when the output changes, it is coupled to the gate of M1 through capacitor C1, providing a path for quickly adjusting the power tube current, thereby accelerating the transient response.

[0086] Next, the transient enhancement effect provided by the present invention is described in conjunction with the transient enhancement LDO simulation result diagrams shown in FIG. 3( a ) and FIG. 3( b ):

[0087] As shown in Figure 3(a), when the load current suddenly changes from 0mA to 100mA, i.e. the IL curve, the overshoot of the conventional structure (without any transient enhancement technology), i.e. the pink curve, reaches 566mV; after the conventional structure is added with active capacitor 3 technology, i.e. the green curve, the overshoot is 216mV; the conventional structure is added with active capacitor 3 technology and classAB SSF, i.e. the red curve, the overshoot is 76mV.

[0088] Figure 3(b) shows the undershoot when the load current suddenly changes from 100mA to 0mA. The undershoot values ​​of the three structures are 368mV, 277mV and 102mV respectively.

[0089] It can be seen from FIG. 3( a ) and FIG. 3( b ) that the technical solution provided by the present invention has a good transient enhancement effect.

[0090] Through the description of the above embodiments, the fast transient response LDO circuit without external capacitors provided by the present invention has at least the following technical effects:

[0091] 1) The present invention is different from the traditional LDO with off-chip filtering large capacitors, but adopts the form of no off-chip capacitors to achieve full on-chip integration to reduce cost and area. For LDO without off-chip capacitors, the present invention adopts active capacitor 3 technology, high-pass filtering technology and classAB super source follower to achieve fast transient response. That is, a monolithic integrated transient enhanced LDO is realized through the classAB super source follower, active capacitor 3 structure and high-pass filter. Compared with the traditional structure, the present invention is more suitable for load mutation situations.

[0092] 2) Use fully symmetrical OTA to achieve large bandwidth to enhance response speed, and use current starvation technology to increase gain to ensure LDO accuracy; use classAB super source follower, active capacitor 3 and high-pass filtering technology to improve the transient response of LDO.

[0093] Although the present invention is described herein in conjunction with various embodiments, in the process of implementing the claimed invention, those skilled in the art may understand and implement other variations of the disclosed embodiments by viewing the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other components or steps, and "one" or "an" does not exclude multiple situations. A single processor or other unit may implement several functions listed in the claims. Certain measures are recorded in different dependent claims, but this does not mean that these measures cannot be combined to produce good results.

[0094] Although the present invention has been described in conjunction with specific features and embodiments thereof, it is apparent that various modifications and combinations may be made thereto without departing from the spirit and scope of the present invention. Accordingly, this specification and the accompanying drawings are merely exemplary illustrations of the present invention as defined by the appended claims and are deemed to cover any and all modifications, variations, combinations or equivalents within the scope of the present invention. Obviously, those skilled in the art may make various modifications and variations to the present invention without departing from the spirit and scope of the present invention. Thus, the present invention is intended to include such modifications and variations if they fall within the scope of the claims of the present invention and their equivalents.

Claims

1. A fast transient response LDO circuit without external capacitor, characterized in that: include: Error amplifier circuit, class AB super source follower circuit and active capacitor; The class AB super source follower circuit is arranged between the error amplifier circuit and the output stage; The class AB super source-follower circuit at least includes a transient response enhancement module; the transient response enhancement module is used to provide a path for adjusting the power tube current and accelerate the transient response; The output stage provides operating current to the load.

2. The fast transient response LDO circuit without external capacitor according to claim 1, characterized in that: The error amplification circuit comprises a first bandwidth extension unit, a second bandwidth extension unit and a gain enhancement unit; the gain enhancement unit is connected between the first bandwidth extension unit and the second bandwidth extension unit; The error amplifier circuit is used to adjust the output voltage; the feedback voltage measured by the sampling circuit at the negative end of the error amplifier circuit becomes smaller, and the reference voltage source measured at the positive end of the error amplifier circuit remains unchanged; the error amplifier circuit outputs a positive difference voltage based on the detected voltage difference, so that the current flowing through the power tube increases and the voltage at the load end increases.

3. The fast transient response LDO circuit without external capacitor according to claim 1, characterized in that: The class AB super source circuit also includes: A super source follower structure; the super source follower structure is connected to the transient response enhancement module; The transient response enhancement module at least includes a first resistor and a first capacitor; the super source follower structure at least includes a first transistor, a second transistor, a third transistor and an eighth transistor.

4. The fast transient response LDO circuit without external capacitor according to claim 3, characterized in that: When the load changes suddenly, the output voltage changes and is coupled to the gate of the first transistor through the first capacitor. The gate of the power tube is regulated by the first transistor and the second transistor to provide transient source current or transient sink current to achieve transient enhancement.

5. The fast transient response LDO circuit without external capacitor according to claim 4, characterized in that: The output voltage is coupled to the drain terminal of the first transistor and then coupled to the gate of the third transistor through the second capacitor, so that the gate of the power transistor is regulated from the drain terminal of the third transistor.

6. The fast transient response LDO circuit without external capacitor according to claim 3, characterized in that: The class AB super source realizes class AB output along with the second transistor, the second resistor and the second capacitor in the circuit; The first transistor, the second transistor, the third transistor, the eighth transistor, the second resistor and the second capacitor in the class AB super source follower circuit realize a super source follower structure. When the output increases or decreases, the gate of the power tube responds to the output voltage change.

7. The fast transient response LDO circuit without external capacitor according to claim 3, characterized in that: In the class AB super source-follower circuit, when the output voltage increases, the gate of the eighth transistor increases, the source of the eighth transistor increases, and the output of the power tube becomes lower, thereby realizing negative feedback regulation; When the output voltage becomes smaller, the gate of the eighth transistor decreases, the source of the eighth transistor decreases, and the output of the power tube becomes higher, thereby realizing negative feedback regulation.

8. The fast transient response LDO circuit without external capacitor according to claim 1, characterized in that: Active capacitors include at least: a fourth transistor, a fifth transistor, a sixth transistor, and a seventh transistor; The active capacitor provides a transient large current to the circuit when the load changes suddenly; When the output voltage decreases, the gate voltage of the sixth transistor decreases, and the current flowing through the sixth transistor increases; When the output voltage increases, the gate voltage of the seventh transistor increases, and the current flowing through the seventh transistor increases.

9. The fast transient response LDO circuit without external capacitor according to claim 8, characterized in that: When the output voltage suddenly changes, the fourth transistor and the fifth transistor amplify the error, and directly adjust the output voltage to be stable through the sixth transistor and the seventh transistor.

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