Charge amplification circuit of atomic force microscope, signal acquisition device and method

Abstract

The embodiment of the invention provides a charge amplification circuit of an atomic force microscope, a signal acquisition device of the atomic force microscope and a signal acquisition method of the atomic force microscope. According to the charge amplification circuit of the atomic force microscope provided by the embodiment of the invention, the charge amplification circuit receives an alternating current output signal of the atomic force microscope, the bandwidth of the charge amplification circuit is 150 Hz-250 kHz, and the charge amplification circuit comprises a first-stage charge amplifier, a second-stage charge amplifier, a third-stage charge amplifier and a fourth-stage charge amplifier, the gain of the first-stage charge amplifier is associated with a first feedback capacitor of the first-stage charge amplifier; the input end of the second-stage voltage amplifier is connected with the output end of the first-stage charge amplifier, and the gain of the second-stage voltage amplifier is associated with a second feedback resistor of the second-stage voltage amplifier.

Description

Technical Field

[0001] The present invention relates to the field of circuit design of atomic force microscopes, and particularly to a charge amplification circuit of an atomic force microscope, a signal acquisition device of an atomic force microscope, and a signal acquisition method of an atomic force microscope. Background Art

[0002] An atomic force microscope (AFM) is an analytical instrument that can be used to study the surface structure of various material materials. It can study the surface structure and properties of materials by detecting the extremely weak interatomic interaction force between the surface of a sample to be measured and a micro force-sensitive element. The surface detection technology of the atomic force microscope can fix one end of a pair of micro-cantilevers that are extremely sensitive to weak forces, and the tiny tip at the other end approaches the sample and interacts with it, so that the acting force deforms the micro-cantilever or changes its motion state. When using an atomic force microscope to scan a sample, these changes can be detected by a sensor, so as to obtain the acting force distribution information and various surface detection information such as surface topography structure information and surface roughness information with nanometer-level resolution.

[0003] When preparing an AFM sensor, it is necessary to use a charge amplification circuit to collect and amplify the output signal of the AFM for surface analysis and detection. The charge amplification circuit can convert a weak charge signal into a low-impedance voltage signal that can be measured and amplified. This conversion process not only enhances the amplitude of the signal but also improves the detection accuracy of the signal. However, there is still a lack of relevant designs for an effective pre-charge amplification circuit in the signal acquisition device of the atomic force microscope.

[0004] Therefore, there is a need for a pre-charge amplification circuit specifically applicable to an atomic force microscope, which has the related design functions of high signal-to-noise ratio, compact structure, simple production, and direct connection to the device feedthrough, so as to realize the signal acquisition and measurement of a high-resolution atomic force microscope. Summary of the Invention

[0005] To solve the above technical problems, according to one aspect of the present invention, a charge amplification circuit of an atomic force microscope is provided, wherein the charge amplification circuit receives the AC output signal of the atomic force microscope, and the bandwidth of the charge amplification circuit is 150 Hz - 250 kHz. The charge amplification circuit includes: a first-stage charge amplifier, the gain of the first-stage charge amplifier is associated with a first feedback capacitor of the first-stage charge amplifier; and a second-stage voltage amplifier, the input end of the second-stage voltage amplifier is connected to the output end of the first-stage charge amplifier, and the gain of the second-stage voltage amplifier is associated with a second feedback resistor of the second-stage voltage amplifier.

[0006] In one example, the first-stage charge amplifier includes: a first input unit, the first input unit includes a first input resistor, a first input capacitor, and a second input resistor connected in sequence, an input end of the first input unit receives an AC output signal of the atomic force microscope, and an output end of the first input unit is respectively connected to an input end of a first feedback unit and an inverting input end of a first amplification unit; a first feedback unit, the first feedback unit includes a first feedback resistor and a first feedback capacitor connected in parallel, and an output end of the first feedback unit is connected to an output end of the first amplification unit; a first amplification unit, the first amplification unit is an inverting amplifier, a non-inverting input end of the inverting amplifier is grounded through a first amplification resistor, and an output end of the inverting amplifier serves as an output end of the first-stage charge amplifier to output a voltage signal; and / or, the second-stage voltage amplifier includes: a second input unit, the second input unit includes a third input resistor, an input end of the second input unit receives the voltage signal output by the first-stage charge amplifier, and an output end of the second input unit is respectively connected to an input end of a second feedback unit and an inverting input end of a second amplification unit; a second feedback unit, the second feedback unit includes a second feedback resistor and a second feedback capacitor connected in parallel, and an output end of the second feedback unit is connected to an output end of the second amplification unit; a second amplification unit, the second amplification unit is a voltage-type operational amplifier, a non-inverting input end of the voltage-type operational amplifier is grounded through a second amplification resistor, and an output end of the voltage-type operational amplifier is connected to an output resistor, serving as an output end of the second-stage voltage amplifier.

[0007] In one example, a decoupling capacitor is further included between the first-stage charge amplifier and the second-stage voltage amplifier; the second-stage voltage amplifier is used to isolate the function of the load circuit and / or to adjust the gain of the charge amplification circuit; the amplification factor of the first-stage charge amplifier is -1 V / pC; the amplification factor of the second-stage voltage amplifier is -1; and / or the amplification factor of the charge amplification circuit is 1 V / pC.

[0008] In one example, the inverting amplifier includes a JFET type operational amplifier; the first input resistor is used to provide impedance matching; the second input resistor is used to provide a bias current for the input of the first amplification unit; the first feedback capacitor is used to determine the output voltage of the first-stage charge amplifier; the low cut-off frequency of the first-stage charge amplifier is determined by the first feedback capacitor and the first feedback resistor; the high cut-off frequency of the first-stage charge amplifier is determined by the first input resistor, the second input resistor, the equivalent series resistance and parallel capacitance of the atomic force microscope, the first input capacitance, and the capacitance of the interface cable connected to the charge amplification circuit; and / or the gain of the second-stage voltage amplifier is proportional to the ratio of the second feedback resistor to the third input resistor.

[0009] In one example, the bandwidth of the charge amplification circuit is 15 kHz - 30 kHz.

[0010] In one example, the bandwidth of the charge amplification circuit is 25 kHz.

[0011] In one example, the charge amplification circuit of the atomic force microscope is a pre-charge amplification circuit of a tuning fork-based atomic force microscope.

[0012] In one example, the charge amplification circuit of the atomic force microscope is a pre-charge amplification circuit of a quality factor enhanced qPlus atomic force microscope.

[0013] According to another aspect of the present invention, there is provided a signal acquisition device for an atomic force microscope, wherein the signal acquisition device includes the charge amplification circuit of the atomic force microscope according to any one of the foregoing.

[0014] According to another aspect of the present invention, there is provided a signal acquisition method for an atomic force microscope, including: receiving the AC output signal of the atomic force microscope; inputting the AC output signal of the atomic force microscope into the charge amplification circuit of the atomic force microscope according to any one of the foregoing to amplify the AC output signal.

[0015] According to the charge amplification circuit of the atomic force microscope, the signal acquisition device of the atomic force microscope, and the signal acquisition method of the atomic force microscope of the present invention, it can be directly connected to the atomic force microscope for signal acquisition, and by adapting the bandwidth of the charge amplification circuit to 150 Hz - 250 kHz and designing the relevant devices and parameters of the charge amplification circuit, a design function with high signal-to-noise ratio, compact structure, and simple fabrication can be obtained to achieve signal acquisition and measurement of a high-resolution atomic force microscope. Description of the Drawings

[0016] The embodiments of the present invention will be described in detail with reference to the accompanying drawings, and the above and other objects, features, and advantages of the present invention will become clearer.

[0017] Figure 1 The structural schematic diagram of the charge amplification circuit of the atomic force microscope according to an embodiment of the present invention is shown; Figure 2 The specific structural schematic diagram of each stage of the amplifier in the charge amplification circuit of the atomic force microscope according to an embodiment of the present invention is shown; Figure 3 The schematic diagram of the specific device arrangement in each stage of the amplifier in the charge amplification circuit of the atomic force microscope according to an embodiment of the present invention is shown; Figures 4(a)-4(c) show examples of the power supply part of the charge amplification circuit of the atomic force microscope according to an embodiment of the present invention; Figure 5 The schematic diagram of the shielding box of the charge amplification circuit of the atomic force microscope according to an embodiment of the present invention is shown; Figure 6 The flowchart of the signal acquisition method of the atomic force microscope according to an embodiment of the present invention is shown. Specific Embodiments

[0018] The charge amplification circuit of the atomic force microscope, the signal acquisition device of the atomic force microscope, and the signal acquisition method of the atomic force microscope according to the embodiments of the present invention will be described below with reference to the accompanying drawings. In the drawings, the same reference numerals always represent the same elements. It should be understood that the embodiments described herein are merely illustrative and should not be construed as limiting the scope of the present invention.

[0019] The charge amplification circuit dedicated to the atomic force microscope is a key device for signal acquisition of the atomic force microscope. Most of the current charge amplification circuits used in atomic force microscopes are relatively large in size, so longer cables are required to connect them to each other. Inevitably, this will introduce noise, thereby affecting the resolution of the atomic force microscope.

[0020] In the embodiments of the present invention, a charge amplification circuit that can be directly connected to the atomic force microscope device for signal acquisition is provided. By adapting the bandwidth of the charge amplification circuit to 150 Hz - 250 kHz and designing the relevant devices and parameters of the charge amplification circuit, a design function with high signal-to-noise ratio, compact structure, and simple production is obtained to achieve the signal acquisition and measurement of a high-resolution atomic force microscope.

[0021] In the embodiment of the present invention, it is considered that the charge amplification circuit is directly connected to the atomic force microscope without using a connecting cable. Thus, first, it is necessary to model the probe in the atomic force microscope that interacts with the material as a voltage source with a series capacitor and resistor, and evaluate the output impedance of the atomic force microscope probe, mainly the magnitude of the capacitive reactance. Subsequently, the structure of the charge amplification circuit can be designed accordingly. The charge amplification circuit can mainly consist of a first-stage charge amplifier (including a feedback network) and a second-stage voltage amplifier.

[0022] Specifically, in the embodiment of the present invention, a charge amplification circuit for an atomic force microscope is provided. Figure 1 FIG. shows a schematic structural diagram of the charge amplification circuit of the atomic force microscope according to the embodiment of the present invention.

[0023] As Figure 1 shown, the charge amplification circuit 1 of the atomic force microscope according to the embodiment of the present invention receives the AC output signal of the atomic force microscope, and the bandwidth of the charge amplification circuit 1 is 150 Hz - 250 kHz. In the embodiment of the present invention, the charge amplification circuit 1 includes: a first-stage charge amplifier 10, the gain of the first-stage charge amplifier 10 is associated with the first feedback capacitor of the first-stage charge amplifier 10; and a second-stage voltage amplifier 20, the input terminal of the second-stage voltage amplifier 20 is connected to the output terminal of the first-stage charge amplifier 10, and the gain of the second-stage voltage amplifier 20 is associated with the second feedback resistor of the second-stage voltage amplifier 20. By setting the bandwidth adaptation value of the charge amplification circuit, and designing the association relationships between the gains of the first-stage charge amplifier and the second-stage voltage amplifier and the corresponding devices respectively, the design functions of high signal-to-noise ratio, compact structure, and simple fabrication can be achieved to realize the signal acquisition and measurement of a high-resolution atomic force microscope.

[0024] In an embodiment of the present invention, after the first-stage charge amplifier has converted the weak signal collected from the AFM terminal into a voltage signal, optionally, the function of the second-stage voltage amplifier can be used to isolate the load circuit and / or to adjust the gain of the charge amplification circuit. In addition, when the second-stage voltage amplifier is used to adjust the gain of the charge amplification circuit, the amplification factor of the second-stage voltage amplifier can be adjusted. For example, in one example, the amplification factor of the first-stage charge amplifier can be -1 V / pC, and the amplification factor of the second-stage voltage amplifier can be -1. Correspondingly, the amplification factor of the charge amplification circuit can be 1 V / pC. Of course, optionally, the above amplification factors can also be selected within other value ranges according to specific application scenarios. For example, the amplification factor of the charge amplification circuit can also be various values such as 0.1 V / pC, 0.2 V / pC, 0.5 V / pC, 0.8 V / pC, 1.2 V / pC, 1.5 V / pC, 2 V / pC, 3 V / pC, 5 V / pC, 10 V / pC, etc.

[0025] In an embodiment of the present invention, the arrangement and connection relationship of each specific device of the charge amplification circuit 1 of the atomic force microscope can be set according to the specific requirements for signal amplification of the atomic force microscope. Figure 2 The specific structural schematic diagrams of each stage of the amplifier in the charge amplification circuit 1 of the atomic force microscope according to an embodiment of the present invention are shown. As Figure 2 shown, the first-stage charge amplifier 10 may include: a first input unit 110 for receiving and inputting a signal to a first amplification unit 130; a first feedback unit 120 for feeding back the signal of the first amplification unit 130; and a first amplification unit 130 for amplifying the received input signal and outputting it. The first input unit 110, the first feedback unit 120, and the first amplification unit 130 in the first-stage charge amplifier 10 may be electrically connected to each other.

[0026] In addition, as Figure 2 shown, the second-stage voltage amplifier 20 may include: a second input unit 210 for receiving and inputting a signal to a second amplification unit 230; a second feedback unit 220 for feeding back the signal of the second amplification unit 230; and a second amplification unit 230 for amplifying the received input signal and outputting it. The second input unit 210, the second feedback unit 220, and the second amplification unit 230 in the second-stage voltage amplifier 20 may be electrically connected to each other.

[0027] In an embodiment of the present invention, the device arrangement among each stage of the amplifier and each unit therein can be set according to the specific application scenario of the atomic force microscope. Figure 3Shows a schematic diagram of the specific device arrangement in each stage of the amplifier in the charge amplification circuit 1 of the atomic force microscope according to an embodiment of the present invention. As Figure 3 shown, the first-stage charge amplifier 10 may include: a first input unit 110, the first input unit 110 includes a first input resistor R8, a first input capacitor C20, and a second input resistor R2 connected in sequence. The input end of the first input unit 110 receives the AC input signal of the atomic force microscope, and the output end of the first input unit 110 is respectively connected to the input end of the first feedback unit 120 and the inverting input end of the first amplification unit 130; a first feedback unit 120, the first feedback unit 120 includes a first feedback resistor R1 and a first feedback capacitor C1 connected in parallel, and the output end of the first feedback unit 120 is connected to the output end of the first amplification unit 130; a first amplification unit 130, the first amplification unit 130 is an inverting amplifier, the non-inverting input end of the inverting amplifier is grounded through a first amplification resistor R3, and the output end of the inverting amplifier is used as the output end of the first-stage charge amplifier 10 to output a voltage signal.

[0028] In addition, in the embodiment of the present invention, as Figure 3 shown, the second-stage voltage amplifier 20 may include: a second input unit 210, the second input unit 210 includes a third input resistor R5, the input end of the second input unit 210 receives the voltage signal output by the first-stage charge amplifier 10, and the output end of the second input unit 210 is respectively connected to the input end of the second feedback unit 220 and the inverting input end of the second amplification unit 230; a second feedback unit 220, the second feedback unit 220 includes a second feedback resistor R4 and a second feedback capacitor C6 connected in parallel, and the output end of the second feedback unit 220 is connected to the output end of the second amplification unit 230; a second amplification unit 230, the second amplification unit 230 is a voltage-type operational amplifier, the non-inverting input end of the voltage-type operational amplifier is grounded through a second amplification resistor R6, and the output end of the voltage-type operational amplifier is connected to an output resistor R7 as the output end of the second-stage voltage amplifier 20.

[0029] Optionally, the charge amplification circuit 1 of the atomic force microscope may further include Figure 3 other structures illustrated in Figure 3 For example, a decoupling capacitor C11 may also be included between the first-stage charge amplifier 10 and the second-stage voltage amplifier 20. The decoupling capacitor C11 is used to provide a stable circuit input, reduce noise coupling to avoid mutual coupling interference. In addition, in the embodiment of the present invention, optionally, various other devices shown in Figure 3The various different pins of each amplifier structure can also be set according to actual needs. The specific values of each device shown in the embodiments of the present invention can also be selected according to the actual application scenarios of the atomic force microscope and are not limited herein.

[0030] In an example of the present invention, further selection and limitation can be made for the models or functions of each device. In one example, the operational amplifier in the inverting amplifier as the first amplification unit 130 can be a JFET type operational amplifier. Additionally, optionally, the first input resistor R8 can be used to provide impedance matching; optionally, the second input resistor R2 can be used to provide a bias current for the input of the first amplification unit 130; optionally, the first feedback capacitor C1 can be used to determine the output voltage of the first-stage charge amplifier 10.

[0031] Furthermore, optionally, the low cutoff frequency f of the first-stage charge amplifier 10 L can be determined by the first feedback capacitor C1 and the first feedback resistor R1. Additionally, optionally, the high cutoff frequency f of the first-stage charge amplifier 10 H can be determined by the first input resistor R8, the second input resistor R2, the equivalent series resistance and parallel capacitance of the atomic force microscope, the first input capacitor C20, and the capacitance of the interface cable connecting the atomic force microscope and the charge amplification circuit 1. Among them, the high cutoff frequency f of the first-stage charge amplifier 10 H plays an important role in the scanning speed and resolution of the AFM.

[0032] In another embodiment of the present invention, optionally, the relationship between the gain of the second-stage voltage amplifier 20 and the second feedback resistor R4 of the second-stage voltage amplifier 20 can be: the gain of the second-stage voltage amplifier 20 is proportional to the ratio of the second feedback resistor R4 to the third input resistor R5, that is, the gain of the second-stage voltage amplifier 20 is proportional to R4 / R5.

[0033] In another embodiment of the present invention, the atomic force microscope charge amplifier circuit 1 may further include a power supply part for supplying power to the circuit. FIGS. 4(a)-4(c) show examples of the power supply part of the atomic force microscope charge amplifier circuit 1 according to an embodiment of the present invention. As shown, a power supply part including two voltage regulators U3 and U4 respectively can be used for power conversion to supply +12V and -12V voltages to the charge amplifier circuit 1 respectively. As shown in FIG. 4(a), the power supply part including the voltage regulator U3 may further include capacitors C12, C15, C21 and resistor R9, which receive the input of the power supply input terminal +15-1 node and provide a +12V output. In addition, as shown in FIG. 4(b), the power supply part including the voltage regulator U4 may further include capacitors C13, C14, C22 and resistor R10, which receive the input of the -15-1 power supply input terminal node and provide a -12V output. In addition, as shown in FIG. 4(c), protection circuits D1 and D2 may be respectively provided at the power supply input terminal nodes +15-1 and -15-1 to prevent damage caused by electrostatic discharge (ESD) or other reasons. Optionally, the model of the diode shown in the figure may be TMBYV10-40FILM. The setting of these protection measures helps to ensure the stability and reliability of the charge amplifier circuit. In the example of the embodiment of the present invention, as shown in FIG. 4(c), capacitors C16, C17, C18 and C19 may also be included, and the specific circuit connection manner thereof will not be described in detail here.

[0034] The above contents such as various selections, arrangements, and connection relationship settings of the specific devices in the atomic force microscope charge amplifier circuit 1 are all examples. In actual applications, they can be adaptively adjusted according to the specific application scenarios of the atomic force microscope, the properties of the materials to be collected, the specific requirements and value ranges of the required signals, etc., and are not limited thereto, and will not be described in detail. According to the specific settings of the above device types, connection relationships, value ranges, and function limitations, a design function with high signal-to-noise ratio, compact structure, and simple manufacturing can be achieved to realize signal acquisition and measurement of a high-resolution atomic force microscope.

[0035] In the embodiment of the present invention, the bandwidth of the charge amplifier circuit may be 150 Hz - 250 kHz. Optionally, the bandwidth of the charge amplifier circuit may be, for example, 10 kHz - 40 kHz. Further, the bandwidth of the charge amplifier circuit is 15 kHz - 30 kHz. Among them, optionally, the bandwidth of the charge amplifier circuit is, for example, 20 kHz, 25 kHz, 28 kHz, etc., and no limitation is made here.

[0036] In the embodiments of the present invention, first, confirm the schematic diagram for fabricating the PCB board according to the above various embodiments. Thereafter, in the embodiments of the present invention, it is also necessary to further reduce the relevant influence of the signal-to-noise ratio for the design of the PCB board and the external shielding box. For example, optionally, the PCB board in the embodiments of the present invention can adopt the design of a double-layer circuit board, which respectively includes a bottom-layer circuit board and a top-layer circuit board. In the design of the PCB board in the embodiments of the present invention, the packages of the various devices constituting the charge amplification circuit can all be surface-mounted. Optionally, most of the capacitors and resistors can be of small packages of 0805 and 0402, which ensures the compactness of the fabricated PCB board structure. In addition, the design of the PCB board in the embodiments of the present invention ensures that the signal flow is from input to output, without signal superposition; and the chips for power conversion and signal processing can be respectively distributed on the upper and lower layers, thereby avoiding signal coupling. In addition, to ensure the shielding effect of the PCB board shielding box as much as possible, copper cladding in contact with the shielding box can be left around the bottom-layer circuit board (for example, it can be achieved by not covering the green oil during the board manufacturing). In addition, four pieces of copper cladding without covering the green oil can also be left on the top-layer circuit board. In one example, the design of the four pieces of the above copper cladding on the top-layer circuit board can be used to realize the fixation with the shielding box.

[0037] Figure 5 FIG. shows a schematic diagram of a shielding box for a charge amplification circuit of an atomic force microscope according to an embodiment of the present invention. As Figure 5 shown, the shielding box of the charge amplification circuit in the embodiment of the present invention can be, for example, about 7 cm * 5 cm, with a very small volume and appropriate weight. Therefore, during the signal acquisition process, the shielding box can be directly connected to the AFM with a BNC without the need for a long cable.

[0038] In the embodiments of the present invention, the atomic force microscope can be a tuning-fork based atomic force microscope, and among them, it can be a quality factor enhanced qPlus atomic force microscope. For the tuning fork, optionally, the charge amplification circuit of the atomic force microscope is a pre-charge amplification circuit of a tuning-fork based atomic force microscope. In one example, the charge amplification circuit of the atomic force microscope is a pre-charge amplification circuit of a quality factor enhanced qPlus atomic force microscope.

[0039] Through the design of the charge amplification circuit of the atomic force microscope in the embodiments of the present invention, by designing the relevant devices and parameters of the charge amplification circuit, a design function with high signal-to-noise ratio, compact structure, and simple fabrication can be obtained to realize the signal acquisition and measurement of a high-resolution atomic force microscope.

[0040] In another embodiment of the present invention, there is also provided a signal acquisition device for an atomic force microscope. Among them, the signal acquisition device may include the charge amplification circuit of the atomic force microscope according to the foregoing embodiment, for signal acquisition and amplification processing of the atomic force microscope.

[0041] In another embodiment of the present invention, there is also provided a signal acquisition method for an atomic force microscope. Figure 6 The flowchart of the signal acquisition method 600 of the atomic force microscope according to an embodiment of the present invention is shown. As Figure 6 shown, the 600 may include: Step 610: Receive the AC output signal of the atomic force microscope.

[0042] Step 620: Input the AC output signal of the atomic force microscope into the charge amplification circuit of the atomic force microscope according to the foregoing, to amplify the AC output signal.

[0043] In the embodiment of the present invention, through the signal acquisition method via the charge amplification circuit of the atomic force microscope in the embodiment of the present invention, a design function with high signal-to-noise ratio, compact structure and simple manufacture can be obtained, so as to realize signal acquisition and measurement of a high-resolution atomic force microscope.

[0044] Of course, the above specific embodiments are only examples and not limitations, and those skilled in the art can combine and combine some steps and devices from the above separately described embodiments according to the concept of the present invention to achieve the effects of the present invention. Such combined embodiments are also included in the present invention, and such combinations are not described one by one here.

[0045] Note that the advantages, benefits, effects, etc. mentioned in the present invention are only examples and not limitations, and it cannot be considered that these advantages, benefits, effects, etc. are essential for each embodiment of the present invention. In addition, the specific details of the above invention are only for the purpose of illustration and easy understanding, rather than limitations. The above details do not limit the present invention to necessarily adopt the above specific details to implement.

[0046] The block diagrams of the devices, apparatuses, equipment, and systems involved in the present invention are only illustrative examples and are not intended to require or imply that they must be connected, arranged, and configured in the manner shown in the block diagrams. As those skilled in the art will recognize, these devices, apparatuses, equipment, and systems can be connected, arranged, and configured in any manner. Words such as "including", "comprising", "having", etc. are open-ended terms, meaning "including but not limited to", and can be used interchangeably with each other. The words "or" and "and" used herein refer to the word "and / or" and can be used interchangeably with it, unless the context clearly indicates otherwise. The word "such as" used herein refers to the phrase "such as but not limited to" and can be used interchangeably with it.

[0047] The flowchart of the steps in the present invention and the above method descriptions are only illustrative examples and are not intended to require or imply that the steps of each embodiment must be carried out in the order given. As those skilled in the art will recognize, the steps in the above embodiments can be carried out in any order. Words such as "thereafter", "then", "next", etc. are not intended to limit the order of the steps; these words are only used to guide the reader through the description of these methods. In addition, any reference to a singular element using the articles "a", "an", or "the" is not to be construed as limiting that element to the singular.

[0048] In addition, the steps and devices in each of the embodiments herein are not limited to being implemented in a particular embodiment. In fact, according to the concept of the present invention, relevant partial steps and partial devices in each of the embodiments herein can be combined to conceive new embodiments, and these new embodiments are also within the scope of the present invention.

[0049] The various operations of the above-described method can be carried out by any suitable means capable of performing the corresponding functions. The means can include various hardware and / or software components and / or modules, including but not limited to circuits, application-specific integrated circuits (ASICs), or processors.

[0050] The various illustrated logic blocks, modules, and circuits can be implemented or carried out using a general-purpose processor, a digital signal processor (DSP), an ASIC, a field-programmable gate array signal (FPGA), or other programmable logic device (PLD), discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. The general-purpose processor can be a microprocessor, but alternatively, the processor can be any commercially available processor, controller, microcontroller, or state machine. The processor can also be implemented as a combination of computing devices, such as a combination of a DSP and a microprocessor, multiple microprocessors, one or more microprocessors cooperating with a DSP core, or any other such configuration.

[0051] The steps of the methods or algorithms described in connection with the present invention may be directly embodied in hardware, in a software module executed by a processor, or in a combination of the two. The software modules may be present in any form of tangible storage medium. Some examples of storage media that may be used include random access memory (RAM), read only memory (ROM), flash memory, EPROM memory, EEPROM memory, registers, a hard disk, a removable disk, a CD-ROM, etc. The storage medium may be coupled to the processor such that the processor can read information from, and write information to, the storage medium. In an alternative, the storage medium may be integral to the processor. The software modules may be a single instruction or many instructions, and may be distributed over several different code segments, different programs, and across multiple storage media.

[0052] The methods of this invention include one or more acts for implementing the described methods. The methods and / or acts may be interchanged with one another without departing from the scope of the claims. In other words, unless a specific order of acts is specified, the order and / or use of specific acts may be modified without departing from the scope of the claims.

[0053] The described functionality may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functionality may be stored as one or more instructions on a tangible computer-readable medium. The storage medium may be any available tangible medium accessible by a computer. By way of example, and not limitation, such computer-readable media may include RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other tangible medium that can be used to carry or store the desired program code in the form of instructions or data structures and that can be accessed by a computer. As used herein, a disc includes a compact disc (CD), a laser disc, an optical disc, a digital versatile disc (DVD), a floppy disk, and a Blu-ray disc.

[0054] Accordingly, a computer program product may perform the operations given herein. For example, such a computer program product may be a computer-readable tangible medium having tangible storage (and / or encoding) thereon of instructions executable by one or more processors to perform the operations described herein. The computer program product may include packaging material.

[0055] Software or instructions may also be transmitted through a transmission medium. For example, the transmission medium may be used to transmit software from a website, server, or other remote source using a transmission medium such as coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, or microwave.

[0056] In addition, the modules and / or other suitable means for performing the methods and techniques described herein can be downloaded and / or otherwise obtained by a user terminal and / or a base station as appropriate. For example, such a device can be coupled to a server to facilitate the transfer of means for performing the methods described herein. Alternatively, the various methods described herein can be provided via a storage component (such as RAM, ROM, a physical storage medium such as a CD or a floppy disk), so that a user terminal and / or a base station can obtain the various methods when coupled to the device or provided with the storage component by the device. In addition, any other suitable techniques for providing the methods and techniques described herein to a device can be utilized.

[0057] Other examples and implementations are within the scope and spirit of the present invention and the appended claims. For example, due to the nature of software, the functions described above can be implemented using software executed by a processor, hardware, firmware, hardwiring, or any combination thereof. The features implementing the functions can also be physically located at various positions, including being distributed so that parts of the functions are implemented at different physical positions. Also, as used herein, including in the claims, the "or" used in the listing of items starting with "at least one" indicates a disjunctive listing, so that for example, the listing of "at least one of A, B, or C" means A or B or C, or AB or AC or BC, or ABC (i.e., A and B and C). In addition, the term "exemplary" does not mean that the examples described are preferred or better than other examples.

[0058] Various changes, substitutions, and alterations to the techniques described herein can be made without departing from the teachings of the technology defined by the appended claims. In addition, the scope of the claims of the present invention is not limited to the specific aspects of the processes, machines, manufactures, compositions of events, means, methods, and acts described above. Processes, machines, manufactures, compositions of events, means, methods, or acts that currently exist or will be developed later and that perform substantially the same function or achieve substantially the same result as the corresponding aspects described herein can be utilized. Accordingly, the appended claims include such processes, machines, manufactures, compositions of events, means, methods, or acts within their scope.

[0059] The foregoing description of the aspects of the invention has been provided to enable any person skilled in the art to make or use the invention. Various modifications to these aspects will be readily apparent to those skilled in the art, and the general principles defined herein can be applied to other aspects without departing from the scope of the invention. Thus, the invention is not intended to be limited to the aspects shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

[0060] The foregoing description has been presented for purposes of illustration and description. Furthermore, this description is not intended to limit embodiments of the invention to the form disclosed herein. Although several example aspects and embodiments have been discussed above, those of skill in the art will recognize some variations, modifications, alterations, additions, and subcombinations thereof.

Claims

1. A charge amplification circuit for an atomic force microscope, wherein, The charge amplification circuit receives the AC output signal of the atomic force microscope, and the bandwidth of the charge amplification circuit is 150 Hz - 250 kHz. The charge amplification circuit includes: A first-stage charge amplifier, where the gain of the first-stage charge amplifier is associated with a first feedback capacitor of the first-stage charge amplifier; and A second-stage voltage amplifier, where the input terminal of the second-stage voltage amplifier is connected to the output terminal of the first-stage charge amplifier, and the gain of the second-stage voltage amplifier is associated with a second feedback resistor of the second-stage voltage amplifier.

2. The charge amplification circuit according to claim 1, wherein The first-stage charge amplifier includes: A first input unit, which includes a first input resistor, a first input capacitor, and a second input resistor connected in sequence. The input terminal of the first input unit receives the AC output signal of the atomic force microscope, and the output terminal of the first input unit is respectively connected to the input terminal of a first feedback unit and the inverting input terminal of a first amplification unit; A first feedback unit, which includes a first feedback resistor and a first feedback capacitor connected in parallel. The output terminal of the first feedback unit is connected to the output terminal of the first amplification unit; A first amplification unit, which is an inverting amplifier. The non-inverting input terminal of the inverting amplifier is grounded through a first amplification resistor, and the output terminal of the inverting amplifier serves as the output terminal of the first-stage charge amplifier to output a voltage signal; and / or The second-stage voltage amplifier includes: A second input unit, which includes a third input resistor. The input terminal of the second input unit receives the voltage signal output by the first-stage charge amplifier, and the output terminal of the second input unit is respectively connected to the input terminal of a second feedback unit and the inverting input terminal of a second amplification unit; A second feedback unit, which includes a second feedback resistor and a second feedback capacitor connected in parallel. The output terminal of the second feedback unit is connected to the output terminal of the second amplification unit; A second amplification unit, which is a voltage-type operational amplifier. The non-inverting input terminal of the voltage-type operational amplifier is grounded through a second amplification resistor, and the output terminal of the voltage-type operational amplifier is connected to an output resistor, serving as the output terminal of the second-stage voltage amplifier.

3. The charge amplification circuit according to claim 1, wherein A decoupling capacitor is further included between the first-stage charge amplifier and the second-stage voltage amplifier; The second-stage voltage amplifier is used for isolating the function of the load circuit and / or for adjusting the gain of the charge amplification circuit; The amplification factor of the first-stage charge amplifier is -1 V / pC; The amplification factor of the second-stage voltage amplifier is -1; and / or The amplification factor of the charge amplification circuit is 1 V / pC.

4. The charge amplification circuit according to claim 2, wherein The inverting amplifier includes a JFET-type operational amplifier; The first input resistor is used to provide impedance matching; The second input resistor is used to provide a bias current for the input of the first amplification unit; The first feedback capacitor is used to determine the output voltage of the first-stage charge amplifier; The lower cutoff frequency of the first-stage charge amplifier is determined by the first feedback capacitor and the first feedback resistor; The upper cutoff frequency of the first-stage charge amplifier is determined by the first input resistor, the second input resistor, the equivalent series resistance and parallel capacitance of the atomic force microscope, the first input capacitance, and the capacitance of the interface cable connected to the charge amplification circuit; and / or The gain of the second-stage voltage amplifier is proportional to the ratio of the second feedback resistor to the third input resistor.

5. The charge amplification circuit according to claim 1, wherein, The bandwidth of the charge amplification circuit is 15 kHz - 30 kHz.

6. The charge amplification circuit according to claim 1, wherein, The bandwidth of the charge amplification circuit is 25 kHz.

7. The charge amplification circuit according to any one of claims 1-6, wherein, The charge amplification circuit of the atomic force microscope is a pre-charge amplification circuit of a tuning fork-based atomic force microscope.

8. The charge amplification circuit according to claim 7, wherein, The charge amplification circuit of the atomic force microscope is a pre-charge amplification circuit of a quality factor-enhanced qPlus atomic force microscope.

9. A signal acquisition device for an atomic force microscope, wherein, The signal acquisition device includes the charge amplification circuit of the atomic force microscope according to any one of claims 1-8.

10. A signal acquisition method for an atomic force microscope, comprising: Receiving the AC output signal of the atomic force microscope; Inputting the AC output signal of the atomic force microscope into the charge amplification circuit of the atomic force microscope according to any one of claims 1-8 to amplify the AC output signal.

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