Filter circuit for quickly responding to LDO (Low Dropout Regulator) and LDO applying same

Abstract

The invention relates to the technical field of low dropout linear voltage regulators, in particular to a filter circuit for a quick response LDO and an LDO applying the filter circuit, the filter circuit is arranged at the output end of the quick response LDO, and the filter circuit comprises a frequency band filter unit, a first shaping filter unit and a second shaping filter unit; the input end of the frequency band filtering unit is used as the input end of the filtering circuit, the frequency band filtering unit, the first shaping filtering unit and the second shaping filtering unit are electrically connected in sequence, and the output end of the second shaping filtering unit is used as the output end of the filtering circuit; the frequency band filtering unit is used for setting a cut-off frequency to filter a non-output signal frequency band; the first shaping filtering unit is used for filtering noise and interference of the signal; the second shaping and filtering unit is used for signal waveform shaping and signal amplification; the problems that an existing filter circuit is poor in filtering capacity, uncontrollable in filtering frequency band and not suitable for a quick response LDO and an application environment of the quick response LDO are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of low voltage drop linear regulators, in particular to a filter circuit for fast response LDO and an application thereof. Background Art

[0002] LDO is a low-dropout linear regulator, which is often used in switching power supplies, especially in high-power and high-voltage switching power supplies. Since high-power and high-voltage switching power supplies usually have a higher switching frequency, this means that there will be more switching actions per unit time. These switching actions will introduce high-frequency noise and clutter, which may propagate to the input of the LDO through the power line and the ground line. At the same time, if the LDO uses a fast-response LDO, the fast-response LDO usually has a larger bandwidth so that it can respond to changes in input voltage and load current more quickly; however, a larger bandwidth also means that more high-frequency noise and clutter may pass through the LDO and be transmitted to the output. Therefore, the fast-response LDO needs to set a filtering circuit at the output end so that the fast-response LDO can match the application environment of the high-power and high-voltage switching power supply, filter out internal and external clutter and noise, and provide high-quality output signals.

[0003] At present, LDO usually only sets a pair of RC tubes at the output end as a filtering circuit, and the filtering ability is limited. As the frequency f increases, the capacitive reactance Xc gradually decreases, that is, the impedance of the capacitor to the high-frequency signal is low, and the filtered output signal frequency band is uncontrollable, and it is easy to filter out the specified frequency band of the output signal; it is not suitable for fast response LDO and cannot adapt to the application environment of fast response LDO. Summary of the invention

[0004] In view of the above defects, the purpose of the present invention is to propose a filter circuit for fast response LDO and its application LDO, which solves the problems that the existing filter circuit has poor filtering ability, uncontrollable filtering frequency band, and cannot be applied to fast response LDO and its application environment.

[0005] To achieve this object, the present invention adopts the following technical solutions:

[0006] A filter circuit for fast response LDO, comprising a frequency band filter unit, a first shaping filter unit and a second shaping filter unit; the input end of the frequency band filter unit is used as the input end of the filter circuit, the output end of the frequency band filter unit is electrically connected to the input end of the first shaping filter unit, the output end of the first shaping filter unit is electrically connected to the input end of the second shaping filter unit, and the output end of the second shaping filter unit is used as the output end of the filter circuit;

[0007] The frequency band filtering unit is used to set a cutoff frequency to filter out non-output signal frequency bands;

[0008] The first shaping filter unit is used to filter out noise and interference of the signal;

[0009] The second shaping and filtering unit is used for signal waveform shaping and signal amplification.

[0010] Further, the frequency band filtering unit includes a response speed setting circuit and a frequency band filter; the input end of the response speed setting circuit is used as the input end of the frequency band filtering unit, the output end of the response speed setting circuit is electrically connected to the input end of the frequency band filter, and the output end of the frequency band filter is used as the output end of the frequency band filtering unit;

[0011] The response speed setting circuit is used to set the on-time of the frequency band filter.

[0012] Furthermore, the response speed setting circuit includes a MOS tube M1 and a MOS tube M2; the gate of the MOS tube M1 is used as the input end of the response speed setting circuit, and the drain of the MOS tube M1 is used as the output end of the response speed setting circuit;

[0013] The source of the MOS tube M1 is connected to the VDD power supply, the gate of the MOS tube M1 is electrically connected to the gate of the MOS tube M2, the drain of the MOS tube M1 is electrically connected to the drain of the MOS tube M2, and the source of the MOS tube M2 is grounded.

[0014] Further, the frequency band filter includes a resistor R and a capacitor C, one end of the resistor R is used as an input end of the frequency band filter, the other end of the resistor R is used as an output end of the frequency band filter, the other end of the resistor R is electrically connected to one end of the capacitor C, and the other end of the capacitor C is grounded;

[0015] The resistor R includes at least two sub-resistors R1, one end of the first sub-resistor R1 is used as one end of the resistor R, and the other end of the last sub-resistor R1 is used as the other end of the resistor R; the other end of the first sub-resistor R1 is electrically connected to one end of the last sub-resistor R1;

[0016] The capacitor C includes at least two sub-capacitors C1 , one end of each sub-capacitor C1 is used as one end of the capacitor C, and the other end of each sub-capacitor C1 is used as the other end of the capacitor C.

[0017] Further, the first shaping filter unit includes MOS tube M3, MOS tube M4, MOS tube M5, MOS tube M6, MOS tube M7, MOS tube M8, resistor R3 and resistor R4; the gate of the MOS tube M4 is used as the input end of the first shaping filter unit, and the gate of the MOS tube M7 is used as the output end of the first shaping filter unit;

[0018] The source of the MOS tube M3 and the source of the MOS tube M7 are both connected to the VDD power supply, the drain of the MOS tube M3 and the source of the MOS tube M4 are both electrically connected to the source of the MOS tube M7, the drain of the MOS tube M7 is electrically connected to one end of the resistor R3, the other end of the resistor R3 is grounded, the gate of the MOS tube M3, the gate of the MOS tube M4, and the gate of the MOS tube M5 are all electrically connected to the gate of the MOS tube M6, the drain of the MOS tube M4 is electrically connected to the drain of the MOS tube M5, the source of the MOS tube M6 and the source of the MOS tube M8 are both grounded, the drain of the MOS tube M6 and the source of the MOS tube M5 are both electrically connected to the source of the MOS tube M8, the drain of the MOS tube M8 is electrically connected to one end of the resistor R4, the other end of the resistor R4 is connected to the VDD power supply, and the gate of the MOS tube M7 is electrically connected to the gate of the MOS tube M8.

[0019] Furthermore, the second shaping filter unit includes a first inverter and a second inverter; the input end of the first inverter is used as the input end of the second shaping filter unit, the output end of the first inverter is electrically connected to the input end of the second inverter, and the output end of the second inverter is used as the output end of the second shaping filter unit.

[0020] Furthermore, the first inverter and the second inverter have the same circuit structure;

[0021] The first inverter includes a MOS tube M9 and a MOS tube M10; the gate of the MOS tube M9 is used as the input end of the first inverter, and the drain of the MOS tube M9 is used as the output end of the first inverter;

[0022] The gate of the MOS tube M9 is electrically connected to the gate of the MOS tube M10, the source of the MOS tube M9 is connected to the VDD power supply, the drain of the MOS tube M9 is electrically connected to the drain of the MOS tube M10, and the source of the MOS tube M10 is grounded.

[0023] A fast response LDO, comprising the above-mentioned filter circuit for fast response LDO; further comprising a bias circuit, a large bandwidth source follower, a reference circuit, a voltage regulator tube D1 and an operational amplifier circuit; the output end of the filter circuit is used as the output end of the fast response LDO;

[0024] The output end of the bias circuit and the cathode of the voltage regulator D1 are electrically connected to the input end of the wide-bandwidth source follower, the output end of the wide-bandwidth source follower is electrically connected to the input end of the reference circuit, the output end of the reference circuit is electrically connected to the input end of the operational amplifier circuit, the output end of the operational amplifier circuit is electrically connected to the input end of the filter circuit, and the anode of the voltage regulator D1 is grounded.

[0025] The technical solution provided by the present invention can include the following beneficial effects: the filter circuit is set at the output end of the fast response LDO, and the non-output signal band is first filtered out by the frequency band filtering unit according to the set cutoff frequency before the signal of the fast response LDO is output, and only the specified signal band is allowed to pass, so as to achieve the frequency band filtering while avoiding the signal band filtering being uncontrollable, and filtering out the specified frequency band of the output signal; then the signal is filtered out by the first shaping filter unit to remove the noise and interference in the signal; finally, the second shaping filter unit shapes the signal, because the waveform of the signal may be distorted due to the influence of various factors (such as noise, attenuation, etc.) during the signal transmission process, and the waveform quality of the signal is restored or improved by the second shaping filter unit through the reprocessing of the signal, so that the waveform of the output signal is closer to the original signal, and the second shaping filter unit also amplifies the signal to improve the signal carrying capacity and maintain the driving capacity of the subsequent circuit. In summary, the filter circuit processes the signal in sequence through three functional modules, enhances the filtering ability of the fast response LDO signal, adapts to high-frequency signals, and can resist high-frequency noise and clutter from the fast response LDO application environment (such as high-power high-voltage switching power supply). BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 The present invention is a circuit diagram of a filter circuit for a fast response LDO according to one embodiment of the present invention.

[0027] Figure 2 It is a schematic diagram of a fast response LDO according to one embodiment of the present invention.

[0028] Among them: frequency band filtering unit 51, first shaping filtering unit 52, second shaping filtering unit 53, response speed setting circuit 511, frequency band filter 512, MOS tube M1, MOS tube M2, resistor R, capacitor C, sub-resistor R1, sub-capacitor C1, MOS tube M3, MOS tube M4, MOS tube M5, MOS tube M6, MOS tube M7, MOS tube M8, resistor R3, resistor R4, first inverter 531, second inverter 532, MOS tube M9, MOS tube M10, bias circuit 1, large bandwidth source follower 2, reference circuit 3, voltage regulator D1, operational amplifier circuit 4, filtering circuit 5. DETAILED DESCRIPTION

[0029] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0030] In the description of the embodiments of the present invention, the terms "first" and "second" are used for descriptive purposes only and are not to be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the embodiments of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0031] In the description of the embodiments of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected or indirectly connected through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the embodiments of the present invention can be understood according to specific circumstances.

[0032] Combine the following Figure 1 to Figure 2 , describing a filter circuit for fast response LDO and its application LDO in an embodiment of the present invention.

[0033] A filter circuit for fast response LDO, comprising a frequency band filter unit 51, a first shaping filter unit 52 and a second shaping filter unit 53; the input end of the frequency band filter unit 51 is used as the input end of the filter circuit, the output end of the frequency band filter unit 51 is electrically connected to the input end of the first shaping filter unit 52, the output end of the first shaping filter unit 52 is electrically connected to the input end of the second shaping filter unit 53, and the output end of the second shaping filter unit 53 is used as the output end of the filter circuit;

[0034] The frequency band filtering unit 51 is used to set the cut-off frequency to filter out the non-output signal frequency band;

[0035] The first shaping filter unit 52 is used to filter out noise and interference of the signal;

[0036] The second shaping filter unit 53 is used for signal waveform shaping and signal amplification.

[0037] The present invention proposes a preferred embodiment of a filter circuit for fast response LDO, such as Figure 1As shown, the signal input is first filtered out by the frequency band filtering unit 51 according to the set cutoff frequency, and only the specified signal frequency band is allowed to pass, so as to achieve frequency band filtering while avoiding the signal frequency band filtering being uncontrollable, and filtering out the specified frequency band of the output signal; then the signal is filtered out by the first shaping filter unit 52 to remove the noise and interference in the signal; finally, the signal is shaped by the second shaping filter unit 53, because the waveform of the signal may be distorted due to the influence of various factors (such as noise, attenuation, etc.) during the signal transmission process, and the waveform quality of the signal is restored or improved by the second shaping filter unit 53 to reprocess the signal, so that the waveform of the output signal is closer to the original signal, and the second shaping filter unit 53 also amplifies the signal to improve the signal's carrying capacity and maintain the driving capacity of the subsequent circuit. In summary, the filter circuit processes the signal in sequence through three functional modules, enhances the filtering ability of the fast response LDO signal, adapts to high-frequency signals, and can resist high-frequency noise and clutter from the fast response LDO application environment (such as high-power high-voltage switching power supply).

[0038] Further, the frequency band filtering unit 51 includes a response speed setting circuit 511 and a frequency band filter 512; the input end of the response speed setting circuit 511 is used as the input end of the frequency band filtering unit 51, the output end of the response speed setting circuit 511 is electrically connected to the input end of the frequency band filter 512, and the output end of the frequency band filter 512 is used as the output end of the frequency band filtering unit 51;

[0039] The response speed setting circuit 511 is used to set the on time of the band filter 512 .

[0040] In this embodiment, the function of the frequency band filtering unit 51 to filter out the non-output signal frequency band according to the cut-off frequency is achieved by setting the on-time of the frequency band filter 512 by the response speed setting circuit 511, that is, by changing the response speed of the response speed setting circuit 511 itself to determine when the signal is transmitted to the frequency band filter 512 and how long it continues to pass, thereby achieving frequency band selection and filtering out the non-output signal frequency band.

[0041] Furthermore, the response speed setting circuit 511 includes a MOS transistor M1 and a MOS transistor M2; the gate of the MOS transistor M1 is used as the input end of the response speed setting circuit 511, and the drain of the MOS transistor M1 is used as the output end of the response speed setting circuit 511;

[0042] The source of the MOS tube M1 is connected to the VDD power supply, the gate of the MOS tube M1 is electrically connected to the gate of the MOS tube M2, the drain of the MOS tube M1 is electrically connected to the drain of the MOS tube M2, and the source of the MOS tube M2 is grounded.

[0043] In this embodiment, the response speed setting circuit 511 is an inverter composed of a MOS tube M1 and a MOS tube M2. The slew rate is affected by adjusting the W / L ratio (width-to-length ratio) of the MOS tube, thereby affecting the response speed of the inverter. The W / L ratio of the MOS tube can be set in advance according to signal requirements.

[0044] Further, the band filter 512 includes a resistor R and a capacitor C, one end of the resistor R is used as an input end of the band filter 512, the other end of the resistor R is used as an output end of the band filter 512, the other end of the resistor R is electrically connected to one end of the capacitor C, and the other end of the capacitor C is grounded;

[0045] The resistor R includes at least two sub-resistors R1, one end of the first sub-resistor R1 is used as one end of the resistor R, and the other end of the last sub-resistor R1 is used as the other end of the resistor R; the other end of the previous sub-resistor R1 is electrically connected to one end of the next sub-resistor R1;

[0046] The capacitor C includes at least two sub-capacitors C1 , one end of each sub-capacitor C1 is used as one end of the capacitor C, and the other end of each sub-capacitor C1 is used as the other end of the capacitor C.

[0047] In this embodiment, the frequency band filter 512 is an RC filter composed of a resistor R and a capacitor C. By designing resistors R with different resistance values ​​and capacitors C with different capacitance values, under the condition that the MOS tube of the response speed setting circuit 511 is fixed at W, by adjusting L in proportion, the RC filter can obtain different cut-off frequencies, play an adjustable filtering function, and filter out unnecessary output signal frequency bands. According to signal requirements, the resistance value of the resistor R and the capacitance value of the capacitor C can be set in advance in cooperation with the response speed setting circuit 511, and the filtering scheme can be determined through simulation to match the high-frequency signal of the fast-response LDO. More importantly, the resistor R is composed of multiple sub-resistors R1 connected in series, and the capacitor C is composed of multiple sub-capacitors C1 connected in parallel, which can improve the simulation accuracy and the final frequency band filtering accuracy, and the filtering effect is better.

[0048] Furthermore, the first shaping filter unit 52 includes a MOS tube M3, a MOS tube M4, a MOS tube M5, a MOS tube M6, a MOS tube M7, a MOS tube M8, a resistor R3 and a resistor R4; the gate of the MOS tube M4 is used as the input end of the first shaping filter unit 52, and the gate of the MOS tube M7 is used as the output end of the first shaping filter unit 52;

[0049] The source of the MOS tube M3 and the source of the MOS tube M7 are both connected to the VDD power supply, the drain of the MOS tube M3 and the source of the MOS tube M4 are both electrically connected to the source of the MOS tube M7, the drain of the MOS tube M7 is electrically connected to one end of the resistor R3, the other end of the resistor R3 is grounded, the gate of the MOS tube M3, the gate of the MOS tube M4, and the gate of the MOS tube M5 are all electrically connected to the gate of the MOS tube M6, the drain of the MOS tube M4 is electrically connected to the drain of the MOS tube M5, the source of the MOS tube M6 and the source of the MOS tube M8 are both grounded, the drain of the MOS tube M6 and the source of the MOS tube M5 are both electrically connected to the source of the MOS tube M8, the drain of the MOS tube M8 is electrically connected to one end of the resistor R4, the other end of the resistor R4 is connected to the VDD power supply, and the gate of the MOS tube M7 is electrically connected to the gate of the MOS tube M8.

[0050] In this embodiment, the first shaping filter unit 52 is a Schmitt trigger composed of MOS tube M3, MOS tube M4, MOS tube M5, MOS tube M6, MOS tube M7, MOS tube M8, resistor R3 and resistor R4. The hysteresis characteristic of the Schmitt trigger can effectively filter out the noise and interference of the signal, and the effect is better. More importantly, by adjusting the width-to-length ratio of the NMOS tube and the PMOS tube in the Schmitt trigger, the forward conduction threshold VTH+ and the negative conduction threshold VTH- of the Schmitt trigger can be adjusted to match the high-frequency signal of the fast response LDO, improve the filtering accuracy, and facilitate the reservation of the threshold margin to prevent misleading conduction.

[0051] Furthermore, the second shaping filter unit 53 includes a first inverter 531 and a second inverter 532; the input end of the first inverter 531 is used as the input end of the second shaping filter unit 53, the output end of the first inverter 531 is electrically connected to the input end of the second inverter 532, and the output end of the second inverter 532 is used as the output end of the second shaping filter unit 53.

[0052] In this embodiment, the signal shaping and signal amplification functions of the second shaping filter unit 53 are implemented by a two-stage inverter. The first inverter 531 receives the input signal and converts it into a form suitable for processing by the second inverter 532, and then the second inverter 532 further processes the signal, thereby achieving signal shaping and amplification through two signal inversions to provide a more stable and reliable output signal.

[0053] Furthermore, the circuit structures of the first inverter 531 and the second inverter 532 are the same;

[0054] The first inverter 531 includes a MOS tube M9 and a MOS tube M10; the gate of the MOS tube M9 is used as the input end of the first inverter 531, and the drain of the MOS tube M9 is used as the output end of the first inverter 531;

[0055] The gate of the MOS tube M9 is electrically connected to the gate of the MOS tube M10, the source of the MOS tube M9 is connected to the VDD power supply, the drain of the MOS tube M9 is electrically connected to the drain of the MOS tube M10, and the source of the MOS tube M10 is grounded.

[0056] In this embodiment, the first inverter 531 and the second inverter 532 are preferably formed by MOS tubes, which can not only realize signal shaping and signal amplification functions, but also play the role of buffering, isolation and impedance matching during signal transmission.

[0057] A fast response LDO, comprising the above-mentioned filter circuit 5 for fast response LDO; further comprising a bias circuit 1, a large bandwidth source follower 2, a reference circuit 3, a voltage regulator D1 and an operational amplifier circuit 4; the output end of the filter circuit 5 is used as the output end of the fast response LDO;

[0058] The output end of the bias circuit 1 and the cathode of the voltage regulator D1 are electrically connected to the input end of the wide bandwidth source follower 2, the output end of the wide bandwidth source follower 2 is electrically connected to the input end of the reference circuit 3, the output end of the reference circuit 3 is electrically connected to the input end of the operational amplifier circuit 4, the output end of the operational amplifier circuit 4 is electrically connected to the input end of the filter circuit 5, and the anode of the voltage regulator D1 is grounded.

[0059] In this embodiment, an embodiment of a fast response LDO is also proposed, such as Figure 2 As shown, the startup circuit composed of the bias circuit 1 and the voltage regulator D1 generates a stable bias voltage. After being buffered and isolated by the large-bandwidth source follower 2, the bias voltage is provided to the reference circuit 3, so that it works at the required static working point, avoiding the reference circuit 3 from entering the zero bias current state, that is, the working current in the circuit is zero and cannot work normally; the reference circuit 3 then generates a reference voltage and provides it to the operational amplifier circuit 4, and the operational amplifier circuit 4 thereby realizes voltage linear adjustment; and because the large-bandwidth source follower 2 is adopted, the linear establishment time of the operational amplifier circuit 4 is greatly shortened, thereby greatly shortening the time for the operational amplifier circuit 4 to respond to the output signal, and finally the output signal is filtered by the end filter circuit 5 and the non-output signal frequency band is filtered out, so as to obtain a better quality output signal, which is more matched with the fast response LDO and adapts to the application environment of the fast response LDO, and avoids signal distortion.

[0060] A filter circuit for fast response LDO according to an embodiment of the present invention and other structures and operations of the LDO used therein are well known to those skilled in the art and will not be described in detail here.

[0061] In the description of this specification, the description with reference to the terms "embodiment", "example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0062] Although the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

Claims

1. A filter circuit for fast response LDO, characterized in that: It comprises a frequency band filtering unit, a first shaping filtering unit and a second shaping filtering unit; the input end of the frequency band filtering unit is used as the input end of the filtering circuit, the output end of the frequency band filtering unit is electrically connected to the input end of the first shaping filtering unit, the output end of the first shaping filtering unit is electrically connected to the input end of the second shaping filtering unit, and the output end of the second shaping filtering unit is used as the output end of the filtering circuit; The frequency band filtering unit is used to set a cutoff frequency to filter out non-output signal frequency bands; The first shaping filter unit is used to filter out noise and interference of the signal; The second shaping and filtering unit is used for signal waveform shaping and signal amplification.

2. A filter circuit for fast response LDO according to claim 1, characterized in that: The frequency band filtering unit comprises a response speed setting circuit and a frequency band filter; the input end of the response speed setting circuit is used as the input end of the frequency band filtering unit, the output end of the response speed setting circuit is electrically connected to the input end of the frequency band filter, and the output end of the frequency band filter is used as the output end of the frequency band filtering unit; The response speed setting circuit is used to set the on-time of the frequency band filter.

3. A filter circuit for fast response LDO according to claim 2, characterized in that: The response speed setting circuit includes a MOS tube M1 and a MOS tube M2; the gate of the MOS tube M1 is used as the input end of the response speed setting circuit, and the drain of the MOS tube M1 is used as the output end of the response speed setting circuit; The source of the MOS tube M1 is connected to the VDD power supply, the gate of the MOS tube M1 is electrically connected to the gate of the MOS tube M2, the drain of the MOS tube M1 is electrically connected to the drain of the MOS tube M2, and the source of the MOS tube M2 is grounded.

4. A filter circuit for fast response LDO according to claim 2, characterized in that: The frequency band filter comprises a resistor R and a capacitor C, one end of the resistor R is used as an input end of the frequency band filter, the other end of the resistor R is used as an output end of the frequency band filter, the other end of the resistor R is electrically connected to one end of the capacitor C, and the other end of the capacitor C is grounded; The resistor R includes at least two sub-resistors R1, one end of the first sub-resistor R1 is used as one end of the resistor R, and the other end of the last sub-resistor R1 is used as the other end of the resistor R; the other end of the first sub-resistor R1 is electrically connected to one end of the last sub-resistor R1; The capacitor C includes at least two sub-capacitors C1 , one end of each sub-capacitor C1 is used as one end of the capacitor C, and the other end of each sub-capacitor C1 is used as the other end of the capacitor C.

5. The filter circuit for fast response LDO according to claim 1, characterized in that: The first shaping filter unit includes MOS tube M3, MOS tube M4, MOS tube M5, MOS tube M6, MOS tube M7, MOS tube M8, resistor R3 and resistor R4; the gate of the MOS tube M4 is used as the input end of the first shaping filter unit, and the gate of the MOS tube M7 is used as the output end of the first shaping filter unit; The source of the MOS tube M3 and the source of the MOS tube M7 are both connected to the VDD power supply, the drain of the MOS tube M3 and the source of the MOS tube M4 are both electrically connected to the source of the MOS tube M7, the drain of the MOS tube M7 is electrically connected to one end of the resistor R3, the other end of the resistor R3 is grounded, the gate of the MOS tube M3, the gate of the MOS tube M4, and the gate of the MOS tube M5 are all electrically connected to the gate of the MOS tube M6, the drain of the MOS tube M4 is electrically connected to the drain of the MOS tube M5, the source of the MOS tube M6 and the source of the MOS tube M8 are both grounded, the drain of the MOS tube M6 and the source of the MOS tube M5 are both electrically connected to the source of the MOS tube M8, the drain of the MOS tube M8 is electrically connected to one end of the resistor R4, the other end of the resistor R4 is connected to the VDD power supply, and the gate of the MOS tube M7 is electrically connected to the gate of the MOS tube M8.

6. A filter circuit for fast response LDO according to claim 1, characterized in that: The second shaping filter unit includes a first inverter and a second inverter; the input end of the first inverter is used as the input end of the second shaping filter unit, the output end of the first inverter is electrically connected to the input end of the second inverter, and the output end of the second inverter is used as the output end of the second shaping filter unit.

7. A filter circuit for fast response LDO according to claim 6, characterized in that: The first inverter and the second inverter have the same circuit structure; The first inverter includes a MOS tube M9 and a MOS tube M10; the gate of the MOS tube M9 is used as the input end of the first inverter, and the drain of the MOS tube M9 is used as the output end of the first inverter; The gate of the MOS tube M9 is electrically connected to the gate of the MOS tube M10, the source of the MOS tube M9 is connected to the VDD power supply, the drain of the MOS tube M9 is electrically connected to the drain of the MOS tube M10, and the source of the MOS tube M10 is grounded.

8. A fast response LDO, characterized in that: A filter circuit for fast response LDO according to any one of claims 1 to 7; a bias circuit, a wide bandwidth source follower, a reference circuit, a voltage regulator D1 and an operational amplifier circuit; the output end of the filter circuit is used as the output end of the fast response LDO; The output end of the bias circuit and the cathode of the voltage regulator D1 are electrically connected to the input end of the wide-bandwidth source follower, the output end of the wide-bandwidth source follower is electrically connected to the input end of the reference circuit, the output end of the reference circuit is electrically connected to the input end of the operational amplifier circuit, the output end of the operational amplifier circuit is electrically connected to the input end of the filter circuit, and the anode of the voltage regulator D1 is grounded.

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