Asymmetric output circuit with doubled output swing and working method thereof

Abstract

The invention discloses an asymmetric output circuit with doubled output swing and a working method thereof, a transimpedance amplifier receives a pulse signal and transmits the pulse signal unidirectionally, a single-ended to differential circuit is connected with a preceding stage transimpedance amplifier circuit, a single-ended signal is converted into a differential signal, and the differential signal is transmitted to the preceding stage transimpedance amplifier circuit. A direct-current voltage difference generated at the output end determines that the output buffer circuit is in an asymmetric state; the asymmetric output buffer circuit is connected with the single-ended to differential circuit and is used for receiving the differential signal and doubling the output swing; the differential pressure holding circuit is connected with the output point of the asymmetric output stage, detects the output conditions of the two points, acts on the input point of the asymmetric buffer circuit, and is used for keeping the stability of the asymmetric state; the output swing is doubled, the use efficiency of current is greatly improved, the analog receiving front-end circuit is suitable for the laser radar, the working power consumption of the analog receiving front-end circuit can be reduced, the integration and heat dissipation requirements of a laser radar system are met, and the use cost of the laser radar system is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of integrated circuits, and in particular relates to an asymmetric output circuit with doubled output swing and a working method thereof. Background Art

[0002] LiDAR (Light Detection and Ranging) is a technology that uses laser pulses to measure distance. It determines the distance of the target object by calculating the time it takes for the laser pulse to be emitted and returned to the receiver. This technology has been widely used in fields such as self-driving cars, remote sensing mapping, robot navigation and environmental monitoring because it can provide high-resolution three-dimensional data.

[0003] Direct Time of Flight (dToF) LiDAR is the mainstream method at present, with its simple structure and high technical maturity. It calculates the distance by measuring the time difference between the emission and reflection of laser pulses. It has the characteristics of simple structure and high technical maturity. With the advancement of hardware technology, the various components of LiDAR are developing towards a more solid, precise, compact and intelligent direction.

[0004] As a key component in the LiDAR, the performance of the receiver directly affects the performance of the entire LiDAR system. However, there are some limitations in the processing of pulsed signals. Due to the low repetition rate and narrow pulse width of the pulse signal, although its peak power is high, the signal received by the receiver has a small DC component and a strong unipolar characteristic. This means that the voltage signal processed by the receiving circuit is unidirectional, rather than alternating between two states like a symmetrical circuit. This characteristic brings challenges to the amplification of the signal and the expansion of the swing in the subsequent circuit.

[0005] In order to further amplify the output signal, the output stage circuit often requires more current consumption, or the system uses an additional post-stage amplifier, which increases the cost and additional power consumption of the lidar system and is not conducive to its integration and miniaturization. In addition, the unipolar signal may also cause other problems during the processing process, such as signal distortion and increased noise. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide an asymmetric output circuit with doubled output swing and a working method thereof in view of the deficiencies in the above-mentioned prior art, so as to solve the technical problem that the laser radar analog front-end circuit has large current and low current efficiency in pursuit of large signal swing output, and the overall power consumption of the laser radar system is large.

[0007] The present invention adopts the following technical solutions: An asymmetric output circuit with doubled output swing, comprising a transimpedance amplifier, wherein the input end of the transimpedance amplifier is connected to a laser radar system, and the output end is connected to an output positive end and an output negative end after sequentially passing through a single-ended to differential circuit, a voltage difference holding circuit and an asymmetric output buffer circuit; The transimpedance amplifier is used to convert the photocurrent signal of the pulse signal into a voltage signal; The single-ended to differential circuit is used to convert a voltage signal into two differential signals and reset the DC levels of the two differential signals; The voltage difference holding circuit is used to detect the output condition of the asymmetric output circuit and maintain the asymmetric state of the asymmetric buffer circuit; The asymmetric output buffer circuit is connected to the single-ended to differential circuit, and is used for receiving the differential signal and realizing the output of the final signal.

[0008] Preferably, the voltage signal converted from the photocurrent signal is unipolar.

[0009] Preferably, the DC voltage difference generated at the output end of the single-ended to differential circuit is used to determine whether the output buffer circuit is in an asymmetric state.

[0010] Preferably, the single-ended to differential circuit includes a current source I S2D , current source I S2D The S poles of the MOS tubes MP1 and MP2 are connected in two ways respectively, the G pole of the MOS tube MP1 is connected to the output end of the transimpedance amplifier, the G pole of the MOS tube MP2 is connected to the output end of the transimpedance amplifier via the resistor R1, and the D poles of the MOS tubes MP1 and MP2 are divided into two ways, one way is connected to the resistor R1 via the resistor array and the capacitor C1, and the other way is respectively connected to the voltage difference holding circuit 4 and the asymmetric output buffer circuit.

[0011] Preferably, the resistor array includes resistors R2 and R3 connected in parallel, and the resistance values ​​of the resistors R2 and R3 are different.

[0012] Preferably, the voltage difference holding circuit includes a current source I os , current source I os The S poles of the MOS tubes MP3 and MP4 are connected to two paths respectively, the G poles of the MOS tubes MP3 and MP4 are connected to the differential amplifier AF, the D poles of the MOS tubes MP3 and MP4 are connected to the single-ended differential circuit and the asymmetric output buffer circuit 5 respectively, the input end of the differential amplifier AF is connected to the first reference voltage and the second reference voltage respectively, and the output end is connected to the output positive end and the output negative end through the level shifter.

[0013] Preferably, the differential amplifier AF detects the voltage difference between the positive output terminal and the negative output terminal and compares it with the first reference voltage and the second reference voltage prefabricated externally, and then clamps the input terminal voltage of the asymmetric output buffer circuit and keeps the input terminal voltage difference always at V preset, making the asymmetric output buffer circuit in an asymmetric state.

[0014] Preferably, the asymmetric output buffer circuit comprises a current source I Buffer , current source I Buffer One end of is grounded, and the other end is connected to the S poles of the MOS tubes MN1 and MN2 respectively. The G poles of the MOS tubes MN1 and MN2 are connected to the single-ended differential circuit and the voltage difference holding circuit respectively. The D pole of the MOS tube MN1 is divided into two paths, one is connected to the output positive end, and the other is connected to one end of the resistor R3. The D pole of the MOS tube MN2 is divided into two paths, one is connected to the output negative end, and the other is connected to one end of the resistor R4. The other end of the resistor R3 is connected to the other end of the resistor R4.

[0015] Preferably, the asymmetric output buffer circuit and the voltage difference holding circuit output simultaneously.

[0016] Another technical solution of the present invention is a working method of an asymmetric output circuit with doubled output swing, comprising the following steps: The transimpedance amplifier transmits the AC signal in the signal to the input end of the single-ended to differential circuit; the single-ended to differential signal converts the signal from a single-ended to a differential signal and transmits it to the asymmetric buffer circuit; The circuit state and asymmetry degree of the asymmetric buffer circuit are jointly determined by the resistor array in the single-ended to differential circuit and the first reference voltage and the second reference voltage applied externally; the swing amplitude of the output signal is expanded by the asymmetric buffer circuit.

[0017] Compared with the prior art, the present invention has at least the following beneficial effects: An asymmetric output circuit with doubled output swing, which re-presets the DC component of the pulse signal and makes the asymmetric output buffer stage circuit work under full current swing; ultimately, without changing the output buffer stage current, the output swing is doubled, which can effectively improve the current utilization rate and simplify the amplification requirements of the post-stage amplifier. It is suitable for pulsed laser radar systems and can reduce the working power consumption of analog receiving front-end circuits, which is beneficial to the integration and heat dissipation requirements of the laser radar system, thereby further reducing the use cost of the laser radar system.

[0018] Furthermore, photodiodes are often connected to analog front-end circuits using a coupling method such as cathode coupling. Since the pulse signal is a single-ended input and the repetition rate is often between 100kHz and 200kHz, the corresponding DC component is very small. Therefore, after the optical signal is converted into a current signal, it often has a unipolar characteristic and continues to be further transmitted through the analog front-end circuit.

[0019] Furthermore, unlike the conventional single-ended to differential circuit, the output DC point of the single-ended to differential circuit proposed in the present invention has a deviation. This DC difference makes the initial working states of the two input MOS tubes of the output buffer stage connected to the single-ended to differential circuit different, which are respectively in a fully turned-on state and a fully turned-off state, which is called an asymmetric state at this time.

[0020] Furthermore, the single-ended to differential circuit further amplifies the single-ended voltage signal transmitted from the front-end transimpedance amplifier, and converts it into two differential signals of equal magnitude and opposite directions through a double-ended output.

[0021] Furthermore, the single-ended to differential circuit uses two unbalanced load resistors, which will cause a DC value deviation at the output end of the single-ended to differential circuit. Controlling the deviation of this DC component will reset the DC common mode value of the differential signal, causing the differential signal to change from the original "fully symmetrical" signal to a "quasi-differential" signal.

[0022] Furthermore, since the voltage difference is formed by the load resistance difference between R2 and R3, it is easily affected by changes in process angle, temperature, and voltage. Therefore, a voltage difference holding circuit is introduced to make the output stage circuit proposed by the present invention more PVT robust.

[0023] Furthermore, a two-stage amplifier is used in the voltage difference holding circuit to increase the loop gain, wherein the first stage is a differential amplifier AF, which is used to set the difference obtained from the input end of the voltage difference holding circuit to be equal to the difference between the reference level 1 and the reference level 2, which is Vpreset and is controllable. Its working mode is very similar to the DC elimination loop used in most limiting amplifiers, but it is worth emphasizing that the target offset difference in the voltage difference holding circuit is Vpreset, while the target offset difference in the DC elimination loop is 0.

[0024] Furthermore, through the control of the single-ended to differential circuit with output bias, the output buffer circuit is in an asymmetric state, which determines that the initial states of the two MOS tubes in the circuit are fully off and fully on. When the pulse signal arrives, the two MOS tubes will switch the working state to fully on and fully off. Specifically, the two paths of the differential pair flow through completely opposite tail currents, and the output swing is doubled.

[0025] A working method of an asymmetric output circuit with doubled output swing. Compared with a symmetrical output circuit under the same power consumption, the proposed asymmetric output circuit with doubled output swing has doubled output swing, which greatly improves the current utilization efficiency and can reduce the working power consumption of an analog receiving front-end circuit.

[0026] In summary, the asymmetric output circuit with doubled output swing and its working method proposed in the present invention are suitable for pulsed laser radar analog front-end circuits, and exhibit low power consumption and large swing output characteristics, which are beneficial to the integration and heat dissipation requirements of the laser radar system, thereby further reducing the use cost of the laser radar system, so that the laser radar can be more suitable for user needs and used in a wider range of scenarios.

[0027] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings to be used in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0029] Figure 1 A schematic diagram of the topological structure of an asymmetric output circuit with doubled output swing according to the present invention; Figure 2 A schematic diagram showing the working state of an asymmetric output circuit with doubled output swing disclosed in the present application and a specific description of the current and output swing; Figure 3 It is a schematic diagram for explaining the working state of the symmetrical output circuit and the current and output swing; Figure 4 The waveform diagram is output by the analog front-end circuit of the present invention after processing a pulse signal input with relatively large intensity, and the conclusion is obtained by including simulation results and test results.

[0030] Among them: 1. Asymmetric output circuit; 2. Transimpedance amplifier; 3. Single-ended to differential circuit; 4. Voltage difference holding circuit; 5. Asymmetric output buffer circuit; 6. Resistor array. DETAILED DESCRIPTION

[0031] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "one side", "one end", "one side" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, in the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0033] In the description 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 a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0034] It should be understood that when used in this specification and the appended claims, the terms "include" and "comprises" indicate the presence of described features, integers, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or combinations thereof.

[0035] It should also be understood that the terms used in the present specification are only for the purpose of describing specific embodiments and are not intended to limit the present invention. As used in the present specification and the appended claims, unless the context clearly indicates otherwise, the singular forms "a", "an" and "the" are intended to include plural forms.

[0036] It should be further understood that the term "and / or" used in the present description and the appended claims refers to any and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0037] Various structural schematic diagrams of the embodiments disclosed in the present invention are shown in the accompanying drawings. These figures are not drawn to scale, and some details are magnified and some details may be omitted for the purpose of clear expression. The shapes of various regions and layers shown in the figures and the relative sizes and positional relationships therebetween are only exemplary, and may deviate in practice due to manufacturing tolerances or technical limitations, and those skilled in the art may additionally design regions / layers with different shapes, sizes, and relative positions according to actual needs.

[0038] The present invention provides an asymmetric output circuit with doubled output swing and a working method thereof, which pre-sets the DC component of a pulse signal and enables the asymmetric output buffer stage circuit to operate under full current swing; ultimately, without changing the output buffer stage current, the output swing is doubled, which can effectively improve the current utilization rate and simplify the amplification requirements of the post-stage amplifier. It is suitable for pulsed laser radar analog front-end circuits and can reduce the working power consumption of the analog receiving front-end circuit, which is beneficial to the integration and heat dissipation requirements of the laser radar system, thereby further reducing the use cost of the laser radar system.

[0039] See also Figure 1 The present invention discloses an asymmetric output circuit with doubled output swing, wherein the asymmetric output circuit 1 comprises a transimpedance amplifier 2, a single-ended to differential circuit 3, a voltage difference holding circuit 4 and an asymmetric output buffer circuit 5; The transimpedance amplifier 2 is used to receive the pulse signal in the laser radar system and convert the photocurrent signal of the pulse signal into a single-ended voltage signal for unidirectional transmission. The input end of the transimpedance amplifier 2 receives the pulse signal received in the laser radar system, and its output end is connected to the single-ended to differential circuit 3.

[0040] The single-ended to differential circuit 3 is used to convert a unipolar voltage signal into two differential signals and reset the DC levels of the two differential signals. The DC voltage difference generated at the output end determines that the output buffer circuit 5 is in an asymmetric state. The output of the single-ended to differential circuit 3 is connected to the output of the voltage difference holding circuit 4 and the input of the asymmetric output buffer circuit 5.

[0041] The resistor array 6 in the single-ended to differential circuit 3 is composed of two resistors R2 and R3 with different resistance values, and generates a voltage difference V at the output end of the single-ended to differential circuit 3. preset , pressure difference V preset It is used to determine that the output buffer circuit 5 is in an asymmetric state.

[0042] The voltage difference holding circuit 4 is used to detect the output condition of the asymmetric output circuit 1 and act on the input point of the asymmetric buffer circuit 5 to maintain the stability of its asymmetric state. The input of the voltage difference holding circuit 4 is connected to the output of the asymmetric output buffer circuit 5, and its output is connected to the input of the asymmetric output buffer circuit 5.

[0043] The asymmetric output buffer circuit 5 is connected to the single-ended to differential circuit 3, and is used to receive the differential signal and double the output swing of the final signal.

[0044] The single-ended to differential circuit 3 includes a current source I S2D, MOS tubes MP1 and MP2, resistors R1, R2, R3, and capacitor C1; among them, MP1 and MP2 are input tubes for amplification, MP1 directly receives the signal from TIA, and the output of the low-pass filter composed of R1 and C1 is connected to MP2; In order to expand the swing, the output offset voltage V preset Forced asymmetric state, output offset voltage V preset It is caused by the asymmetric loads R2 and R3, with a resistance difference of ΔR.

[0045] The capacitance and resistance of the filter capacitor C1 , the filter resistor R1 , and the resistor arrays R2 and R3 are all within a preset range.

[0046] Specifically, the voltage difference holding circuit 4 includes a current source I os , differential amplifier, MOS tubes MP3, MP4, and a level shifter and a first reference voltage and a second reference voltage.

[0047] The input of the voltage difference holding circuit 4 is connected to the output of the asymmetric output buffer circuit 5, and the output of the voltage difference holding circuit 4 is connected to the input of the asymmetric output buffer circuit 5. By detecting the voltage difference between the output positive terminal and the output negative terminal and comparing it with the external pre-made first reference voltage and second reference voltage, the input terminal voltage of the asymmetric output buffer circuit 5 is clamped, and the input terminal voltage difference is always kept at V preset , which also determines that the asymmetric output buffer circuit 5 is in an asymmetric state. The level shifter migrates the level while ensuring that the voltage difference remains unchanged, and ensures that the difference in voltage received at the input point is set to V through the differential amplifier (DDA). ref1 -V ref2 The voltage difference is further amplified by the source followers of MOS tube MP3 and MOS tube MP4 to maintain the voltage difference.

[0048] The selected values ​​of the level shifter and the first reference voltage and the second reference voltage are all within a preset range.

[0049] Specifically, the asymmetric output buffer circuit 5 includes: a current source I Buffer , resistors R4, R5, MOS tubes MN1, MN2; among which MN1, MN2 are input amplifier tubes, and the load resistor R satisfies the impedance matching.

[0050] The input end of the asymmetric output buffer circuit 5 is connected to the output of the single-ended to differential circuit 3, and the output end is connected to the voltage difference holding circuit 4 for simultaneous output; due to the unbalanced voltage difference V preset This puts the asymmetric output buffer circuit 5 in an asymmetric state and causes the output swing to double.

[0051] The present invention provides a working method of an asymmetric output circuit with doubled output swing, comprising the following steps: The transimpedance amplifier transmits the AC signal in the signal to the input end of the single-ended to differential circuit, and the single-ended to differential circuit converts the signal from single-ended to differential signal and transmits it to the asymmetric buffer circuit. The circuit state and asymmetry of the asymmetric buffer circuit are jointly determined by the resistor array in the single-ended to differential circuit and the first reference voltage and the second reference voltage applied externally; and the asymmetric buffer circuit will expand and double the swing of the output signal.

[0052] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. The components of the embodiments of the present invention described and shown in the drawings here can usually be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0053] Compared with the symmetrical output circuit with the same power consumption, the asymmetric output circuit with doubled output swing of the present invention will show lower power consumption and doubled output swing characteristics. That is, the asymmetry will enable a 2-fold output swing under the same bias current. This is because there is basically no DC signal in the signal pulse of the APD of the pulsed laser radar, resulting in the output of the TIA being unipolar. This is also different from the performance of the continuous-time DC-coupled PD-TIA. Therefore, by resetting the common-mode level of the differential signal, the signal at the output end of the circuit is changed from a fully symmetrical signal to a quasi-fully differential signal, so that the two paths of the differential pair of the output buffer stage flow full currents in opposite directions, and the system finally obtains a double output swing under the same tail current.

[0054] See also Figure 2 , assuming that the input signal is a unipolar pulse with only negative direction, then after the output of the transimpedance amplifier, the signal will only have a positive voltage swing. In the traditional solution, the single-ended to differential circuit used will convert the single-ended signal into two signals VIN1 / VIN2 with the same DC operating point and opposite polarity but the same amplitude. VIN1 and VIN2 determine the working state of MN1 and MN2. When the signal arrives, the current in MN1 and MN2 changes from tail current 0.5I to tail current 1. B Change to I B and 0, resulting in a differential tail current change of IB To ensure output impedance matching, the total output resistance RL is 25Ω, and the differential output swing can be expressed as I B R L .

[0055] Therefore, in this way, using only the positive portion of the input in the buffer, the signal output swing of the overall output stage will only reach half of the maximum voltage swing in the buffer, which results in half of the tail current being wasted.

[0056] See also Figure 3 , the asymmetric state means that the tail current I B In the initial state, only one signal path flows; when the pulse signal arrives, I B Turn to another path; if all I B If both paths flow through the other path, the output swing will be maximum; in this case, the signal at the output of the circuit becomes a true fully differential signal.

[0057] Specifically, in the initial state, all tail current flows through MN2. When the pulse signal arrives, I B is directed from MN2 to MN1. The current in MN2 is from I B becomes 0, and the current in MN1 changes from 0 to I B , resulting in a differential current change of 2I B , the differential output swing is 2I B R L .and Figure 2 As shown, compared with the symmetrical output stage, the method of the present invention achieves twice the output swing at the same tail current.

[0058] See also Figure 4 , showing the waveform output by the analog front-end circuit of the present invention after processing a relatively strong pulse signal input. When the input is a 200 μA signal, the circuit enters a saturated state. When the output stage circuit uses only 40 mA, the output swing reaches nearly 2V pp,diff This can be proved by both simulation results and test results, which ensures the effectiveness and reliability of the present invention.

[0059] In summary, the present invention provides an asymmetric output circuit with doubled output swing and its working method, by re-presetting the DC component of the pulse signal and making the asymmetric output buffer stage circuit work under full current swing. Finally, without changing the output buffer stage current, the output swing is doubled, which can effectively improve the current utilization rate and simplify the amplification requirements of the post-stage amplifier. It is suitable for pulsed laser radar systems, and can reduce the working power consumption of the analog receiving front-end circuit, which is beneficial to the integration and heat dissipation requirements of the laser radar system, thereby further reducing the use cost of the laser radar system.

[0060] The above contents are only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. An asymmetric output circuit with doubled output swing, characterized in that: It comprises a transimpedance amplifier (2), the input end of the transimpedance amplifier (2) is connected to the laser radar system, and the output end is connected to the output positive end and the output negative end after passing through a single-ended differential conversion circuit (3), a voltage difference holding circuit (4) and an asymmetric output buffer circuit (5) in sequence; The transimpedance amplifier (2) is used to convert the photocurrent signal of the pulse signal into a voltage signal; The single-ended to differential circuit (3) is used to convert the voltage signal into two differential signals and reset the DC levels of the two differential signals; The voltage difference holding circuit (4) is used to detect the output condition of the asymmetric output circuit and maintain the asymmetric state of the asymmetric buffer circuit; The asymmetric output buffer circuit (5) is connected to the single-ended to differential circuit (3) and is used to receive the differential signal and output the final signal.

2. The asymmetric output circuit with doubled output swing and the working method thereof according to claim 1, characterized in that: The voltage signal converted from the photocurrent signal is unipolar.

3. The asymmetric output circuit with doubled output swing and the working method thereof according to claim 1, characterized in that: The DC voltage difference generated at the output end of the single-ended to differential circuit (3) is used to determine whether the output buffer circuit (5) is in an asymmetric state.

4. The asymmetric output circuit with doubled output swing and the working method thereof according to claim 3, characterized in that: The single-ended to differential circuit (3) includes a current source I S2D , current source I S2D The S poles of the MOS tubes MP1 and MP2 are connected in two paths respectively; the G pole of the MOS tube MP1 is connected to the output end of the transimpedance amplifier (2); the G pole of the MOS tube MP2 is connected to the output end of the transimpedance amplifier (2) via the resistor R1; the D poles of the MOS tubes MP1 and MP2 are connected in two paths; one path is connected to the resistor R1 via the resistor array (6) and the capacitor C1; and the other path is connected to the voltage difference holding circuit 4 and the asymmetric output buffer circuit (5).

5. The asymmetric output circuit with doubled output swing and the working method thereof according to claim 4, characterized in that: The resistor array (6) includes resistors R2 and R3 connected in parallel, and the resistance values ​​of the resistors R2 and R3 are different.

6. The asymmetric output circuit with doubled output swing and the working method thereof according to claim 1, characterized in that: The voltage difference holding circuit (4) includes a current source I os , current source I os The S poles of the MOS tubes MP3 and MP4 are connected in two ways respectively; the G poles of the MOS tubes MP3 and MP4 are connected to the differential amplifier AF; the D poles of the MOS tubes MP3 and MP4 are connected to the single-ended differential conversion circuit (3) and the asymmetric output buffer circuit 5 respectively; the input end of the differential amplifier AF is connected to the first reference voltage and the second reference voltage respectively; and the output end is connected to the output positive end and the output negative end via the level shifter.

7. The asymmetric output circuit with doubled output swing and the working method thereof according to claim 6, characterized in that: The differential amplifier AF detects the voltage difference between the positive output terminal and the negative output terminal and compares it with the first reference voltage and the second reference voltage pre-made externally, and then clamps the input voltage of the asymmetric output buffer circuit (5) and keeps the input voltage difference always at V preset , so that the asymmetric output buffer circuit (5) is in an asymmetric state.

8. The asymmetric output circuit with doubled output swing and the working method thereof according to claim 1, characterized in that: The asymmetric output buffer circuit (5) includes a current source I Buffer , current source I Buffer One end of the MOS tube MN1 is grounded, and the other end is connected to the S poles of the MOS tubes MN1 and MN2 respectively; the G poles of the MOS tubes MN1 and MN2 are connected to the single-ended differential conversion circuit (3) and the voltage difference holding circuit (4) respectively; the D pole of the MOS tube MN1 is divided into two paths, one path is connected to the output positive end, and the other path is connected to one end of the resistor R3; the D pole of the MOS tube MN2 is divided into two paths, one path is connected to the output negative end, and the other path is connected to one end of the resistor R4; the other end of the resistor R3 is connected to the other end of the resistor R4.

9. The asymmetric output circuit with doubled output swing and the working method thereof according to claim 8, characterized in that: The asymmetric output buffer circuit (5) and the voltage difference holding circuit (4) output simultaneously.

10. The working method of the asymmetric output circuit with doubled output swing according to any one of claims 1 to 9, characterized in that: The following steps are involved: The transimpedance amplifier transmits the AC signal in the signal to the input end of the single-ended to differential circuit; the single-ended to differential signal converts the signal from a single-ended to a differential signal and transmits it to the asymmetric buffer circuit; The circuit state and asymmetry degree of the asymmetric buffer circuit are jointly determined by the resistor array in the single-ended to differential circuit and the first reference voltage and the second reference voltage applied externally; the swing amplitude of the output signal is expanded by the asymmetric buffer circuit.

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