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

Abstract

Embodiments of the present invention provide a charge amplification circuit for an atomic force microscope, a signal acquisition device for an atomic force microscope, and a signal acquisition method for an atomic force microscope. The charge amplification circuit for an atomic force microscope provided by an embodiment of the present invention receives an AC output signal from the atomic force microscope, and has a bandwidth of 150 Hz to 250 kHz. The charge amplification circuit includes: a first-stage charge amplifier, the gain of which is associated with a first feedback capacitor of the first-stage charge amplifier; and a second-stage voltage amplifier, the input of which is connected to the output of the first-stage charge amplifier, and the gain of which 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 in particular 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] The atomic force microscope (AFM) is an analytical instrument used to study the surface structure of various materials. It investigates the surface structure and properties of materials by detecting the extremely weak interatomic forces between the surface of the sample being tested and a miniature force-sensitive element. AFM surface detection technology involves fixing one end of a pair of extremely sensitive microcantilevers, each of which is extremely sensitive to weak forces, while a tiny tip at the other end approaches the sample and interacts with it, causing the applied force to deform or change the motion of the cantilever. When scanning the sample with the AFM, sensors can detect these changes, thereby obtaining information on the force distribution and, with nanometer-level resolution, various surface detection information, including surface topography and surface roughness.

[0003] When fabricating an AFM sensor, a charge amplifier circuit is required to collect and amplify the AFM's output signal for surface analysis and detection. This circuit converts the weak charge signal into a low-impedance voltage signal that can be measured and amplified. This conversion process not only enhances the signal amplitude but also improves detection accuracy. However, effective pre-charge amplifier circuit designs for the signal acquisition system of an atomic force microscope remain lacking.

[0004] Therefore, a pre-charge amplifier circuit specifically suitable for atomic force microscopes is needed, which has high signal-to-noise ratio, compact structure, simple manufacturing, and related design functions that can be directly connected to the device feedthrough to achieve high-resolution atomic force microscope signal acquisition and measurement. Summary of the Invention

[0005] To solve the above technical problems, according to one aspect of the present invention, a charge amplifier circuit for an atomic force microscope is provided, wherein the charge amplifier circuit receives the AC output signal of the atomic force microscope, and the bandwidth of the charge amplifier circuit is 150 Hz-250 kHz, and the charge amplifier 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, the input end of the first input unit receives the AC output signal of the atomic force microscope, and the output end of the first input unit is respectively connected to the input end of the first feedback unit and the inverting input end of the first amplifying unit; a first feedback unit, the first feedback unit includes a first feedback resistor and a first feedback capacitor connected in parallel, the output end of the first feedback unit is connected to the output end of the first amplifying unit; a first amplifying unit, the first amplifying unit is an inverting amplifier, the non-inverting input end of the inverting amplifier is grounded via the first amplifying resistor, and the output end of the inverting amplifier serves as the output end of the first-stage charge amplifier, and the output Output voltage signal; and / or, the second-stage voltage amplifier includes: a second input unit, the second input unit includes a third input resistor, the input end of the second input unit receives the voltage signal output by the first-stage charge amplifier, and the output end of the second input unit is respectively connected to the input end of the second feedback unit and the inverting input end of the second amplifying unit; a second feedback unit, the second feedback unit includes a second feedback resistor and a second feedback capacitor connected in parallel, and the output end of the second feedback unit is connected to the output end of the second amplifying unit; a second amplifying unit, the second amplifying unit is a voltage-type operational amplifier, the non-inverting input end of the voltage-type operational amplifier is grounded via the second amplifying resistor, and the output end of the voltage-type operational amplifier is connected to the output resistor as the 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 load circuit and / or to adjust the gain of the charge amplifier 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 amplifier 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 first amplification unit input; 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 capacitor, 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 amplifier circuit is 15 kHz-30 kHz.

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

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

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

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

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

[0015] The charge amplifier circuit, signal acquisition device, and signal acquisition method for an atomic force microscope according to the present invention can be directly connected to an atomic force microscope for signal acquisition. By adapting the bandwidth of the charge amplifier circuit to 150 Hz-250 kHz and designing related components and parameters of the charge amplifier circuit, a design function with a high signal-to-noise ratio, a compact structure, and simple fabrication is obtained, thereby realizing high-resolution signal acquisition and measurement of an atomic force microscope. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The above and other objects, features and advantages of the present invention will become more apparent by describing in detail the embodiments of the present invention with reference to the accompanying drawings.

[0017] Figure 1 A schematic structural diagram of a charge amplification circuit of an atomic force microscope according to an embodiment of the present invention is shown;

[0018] Figure 2 A schematic diagram showing the specific structures of amplifiers at various levels in a charge amplification circuit of an atomic force microscope according to an embodiment of the present invention is shown;

[0019] Figure 3 A schematic diagram showing the arrangement of specific devices in each amplifier stage in a charge amplification circuit of an atomic force microscope according to an embodiment of the present invention is shown;

[0020] 4( a ) to 4 ( c ) illustrate an example of a power supply portion of a charge amplification circuit of an atomic force microscope according to an embodiment of the present invention;

[0021] Figure 5 A schematic diagram showing a shielding box for a charge amplification circuit of an atomic force microscope according to an embodiment of the present invention is shown;

[0022] Figure 6 A flow chart showing a signal acquisition method for an atomic force microscope according to an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0023] The following describes a charge amplification circuit for an atomic force microscope, a signal acquisition device for an atomic force microscope, and a signal acquisition method for an atomic force microscope according to embodiments of the present invention with reference to the accompanying drawings. In the accompanying drawings, like reference numerals represent like elements throughout. 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.

[0024] A dedicated charge amplifier circuit for atomic force microscopes (AFMs) is a key device for signal acquisition. Currently, most charge amplifier circuits used in AFMs are large, requiring long cables to connect them. This inevitably introduces noise, which affects the AFM's resolution.

[0025] In an embodiment of the present invention, a charge amplifier circuit is provided that can be directly connected to an atomic force microscope device for collecting signals. By adapting the bandwidth of the charge amplifier circuit to 150 Hz-250 kHz and designing related components and parameters of the charge amplifier circuit, a design function with a high signal-to-noise ratio, a compact structure, and simple fabrication is obtained, thereby realizing high-resolution signal collection and measurement of atomic force microscopes.

[0026] In an embodiment of the present invention, it is considered possible to connect the charge amplifier circuit directly to the atomic force microscope without a connecting cable. Therefore, it is necessary to first consider modeling the probe used in the atomic force microscope to interact with the material as a voltage source with a series capacitor and resistor, and to evaluate the output impedance of the atomic force microscope probe, primarily the capacitive reactance. Subsequently, the structure of the charge amplifier circuit can be designed accordingly. This charge amplifier circuit can primarily consist of a first-stage charge amplifier (including a feedback network) and a second-stage voltage amplifier.

[0027] Specifically, in an embodiment of the present invention, a charge amplification circuit for an atomic force microscope is provided. Figure 1 A schematic structural diagram of a charge amplification circuit of an atomic force microscope according to an embodiment of the present invention is shown.

[0028] like Figure 1 As shown, the charge amplifier circuit 1 of an atomic force microscope according to an embodiment of the present invention receives the AC output signal of the atomic force microscope, and the bandwidth of the charge amplifier circuit 1 is 150 Hz-250 kHz. In this embodiment of the present invention, the charge amplifier circuit 1 includes: a first-stage charge amplifier 10, the gain of which is associated with a first feedback capacitor of the first-stage charge amplifier 10; and a second-stage voltage amplifier 20, the input of which is connected to the output of the first-stage charge amplifier 10, and the gain of which is associated with a second feedback resistor of the second-stage voltage amplifier 20. By setting the bandwidth adaptation value of the charge amplifier circuit and designing the relationship between the gains of the first-stage charge amplifier and the second-stage voltage amplifier and their components, a high signal-to-noise ratio, a compact structure, and simple fabrication can be achieved, thereby enabling high-resolution signal acquisition and measurement for an atomic force microscope.

[0029] In an embodiment of the present invention, after the first-stage charge amplifier has converted the weak signal collected from the AFM end into a voltage signal, the second-stage voltage amplifier can optionally be used to isolate the load circuit and / or adjust the gain of the charge amplifier circuit. Furthermore, when the second-stage voltage amplifier is used to adjust the gain of the charge amplifier 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. Accordingly, the amplification factor of the charge amplifier circuit can be 1 V / pC. Of course, the amplification factors can also be selected from other value ranges based on the specific application scenario. For example, the amplification factor of the charge amplifier 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.

[0030] In the embodiment of the present invention, the arrangement and connection relationship of each specific component 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 FIG. 1 is a schematic diagram showing the specific structure of each amplifier in the charge amplifier circuit 1 of the atomic force microscope according to an embodiment of the present invention. Figure 2 As shown, the first-stage charge amplifier 10 may include: a first input unit 110 for receiving a signal and inputting it into a first amplifying unit 130; a first feedback unit 120 for providing feedback to the signal of the first amplifying unit 130; and the first amplifying unit 130 for amplifying and outputting the received input signal. The first input unit 110, the first feedback unit 120, and the first amplifying unit 130 in the first-stage charge amplifier 10 may be electrically connected to each other.

[0031] In addition, if Figure 2 As shown, the second-stage voltage amplifier 20 may include: a second input unit 210 for receiving a signal and inputting it into a second amplifying unit 230; a second feedback unit 220 for providing feedback to the signal of the second amplifying unit 230; and the second amplifying unit 230 for amplifying and outputting the received input signal. The second input unit 210, the second feedback unit 220, and the second amplifying unit 230 in the second-stage voltage amplifier 20 may be electrically connected to each other.

[0032] In one embodiment of the present invention, the arrangement of devices between each amplifier stage and each unit therein can be set according to the specific application scenario of the atomic force microscope. Figure 3FIG. 1 is a schematic diagram showing the arrangement of specific devices in each amplifier stage in the charge amplifier circuit 1 of the atomic force microscope according to an embodiment of the present invention. Figure 3 As 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 amplifying 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, the output end of the first feedback unit 120 is connected to the output end of the first amplifying unit 130; the first amplifying unit 130, the first amplifying unit 130 is an inverting amplifier, the non-inverting input end of the inverting amplifier is grounded via the first amplifying resistor R3, and the output end of the inverting amplifier serves as the output end of the first-stage charge amplifier 10, outputting a voltage signal.

[0033] In addition, in the embodiment of the present invention, Figure 3 As 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 amplifying 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 amplifying unit 230; a second amplifying unit 230, the second amplifying unit 230 is a voltage-type operational amplifier, the non-inverting input end of the voltage-type operational amplifier is grounded via the second amplifying resistor R6, and the output end of the voltage-type operational amplifier is connected to the output resistor R7, serving as the output end of the second-stage voltage amplifier 20.

[0034] Optionally, the charge amplifier circuit 1 of the atomic force microscope may further include: Figure 3 For example, a decoupling capacitor C11 may 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, and avoid mutual coupling interference. In addition, in the embodiment of the present invention, optionally, the circuits may further include: Figure 3 The other components shown in , such as C2, C3, C4, C5, C7, C8, C9, C10, etc. Figure 3The various pins of the amplifier structures can also be set according to actual needs. The specific values ​​of the various components shown in the embodiment of the present invention can also be selected according to the actual application scenario of the atomic force microscope, and are not limited here.

[0035] In one example of the present invention, further selection and restrictions can be made based on the model or function of each device. In one example, the operational amplifier in the inverting amplifier serving as the first amplifying unit 130 can be a JFET operational amplifier. Furthermore, the first input resistor R8 can optionally be used to provide impedance matching; the second input resistor R2 can optionally be used to provide a bias current for the input of the first amplifying unit 130; and the first feedback capacitor C1 can optionally be used to determine the output voltage of the first-stage charge amplifier 10.

[0036] Further, optionally, the lower cutoff frequency f of the first stage charge amplifier 10 is L It can be determined by the first feedback capacitor C1 and the first feedback resistor R1. In addition, optionally, the upper limit cutoff frequency f of the first stage charge amplifier 10 is H It 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 amplifier circuit 1. H It plays an important role in the scanning speed and resolution of AFM.

[0037] 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.

[0038] In another embodiment of the present invention, the atomic force microscope charge amplifier circuit 1 may further include a power supply for supplying power to the circuit. Figures 4(a)-4(c) illustrate an example of a power supply for an atomic force microscope charge amplifier circuit 1 according to an embodiment of the present invention. As shown, a power supply section comprising two voltage-regulated power supplies, U3 and U4, may be employed for power conversion to provide +12V and -12V voltages, respectively, to the charge amplifier circuit 1. As shown in Figure 4(a), the power supply section comprising voltage-regulated power supply U3 may further include capacitors C12, C15, and C21, and a resistor R9, which receive input from the power supply input node +15-1 and provide a +12V output. Furthermore, as shown in Figure 4(b), the power supply section comprising voltage-regulated power supply U4 may further include capacitors C13, C14, and C22, and a resistor R10, which receive input from the -15-1 power supply input node and provide a -12V output. Furthermore, as shown in Figure 4(c), protection circuits D1 and D2 can be installed at the power input nodes +15-1 and -15-1, respectively, to prevent damage due to electrostatic discharge (ESD) or other causes. Optionally, the diode model shown in the figure can be TMBYV10-40FILM. These protective measures help ensure the stability and reliability of the charge amplifier circuit. In an example embodiment of the present invention, as shown in Figure 4(c), capacitors C16, C17, C18, and C19 may also be included. Their specific circuit connections are not detailed here.

[0039] The above-described selection, arrangement, and connection relationship settings of specific components in the atomic force microscope charge amplifier circuit 1 are merely examples. In actual applications, adaptive adjustments can be made based on the specific application scenario of the atomic force microscope, the properties of the collected materials, the specific requirements and value range of the desired signal, etc., without limitation to these, and will not be repeated here. Based on the specific settings of the above-mentioned component types, connection relationships, value ranges, and functional limitations, a high signal-to-noise ratio, a compact structure, and simple fabrication can be achieved, thereby realizing high-resolution signal acquisition and measurement for atomic force microscopy.

[0040] In an 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 may be 15 kHz-30 kHz. Optionally, the bandwidth of the charge amplifier circuit may be, for example, 20 kHz, 25 kHz, 28 kHz, etc., without limitation herein.

[0041] In an embodiment of the present invention, a schematic diagram for preparing a PCB is first determined based on the aforementioned embodiments. Subsequently, in an embodiment of the present invention, the design of the PCB and the external shielding box are further optimized to minimize the impact of signal-to-noise ratio. For example, the PCB in an embodiment of the present invention can optionally employ a two-layer design, comprising a bottom and top circuit boards. In the PCB design of an embodiment of the present invention, the packages of the components comprising the charge amplifier circuit can all be surface-mount devices. Optionally, most of the capacitors and resistors can be small 0805 and 0402 packages, ensuring the compactness of the resulting PCB. Furthermore, the PCB design in an embodiment of the present invention ensures that signals flow from input to output without signal overlap. The power conversion and signal processing chips can be distributed separately on the top and bottom layers, thereby preventing signal coupling. Furthermore, to maximize the shielding effectiveness of the PCB shielding box, copper cladding can be left around the bottom circuit board, contacting the shielding box (for example, this can be achieved by leaving the copper cladding uncovered during board fabrication). Similarly, four copper claddings, uncovered by the copper cladding, can also be left on the top circuit board. In one example, the four copper clad pieces of the top circuit board can be used to achieve confinement with the shielding box.

[0042] Figure 5 FIG. 1 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. Figure 5 As shown, the shielding box of the charge amplifier circuit of the embodiment of the present invention can be, for example, approximately 7 cm by 5 cm, which is very small and of suitable weight. Therefore, during the signal acquisition process, the shielding box can be directly connected to the AFM via BNC without the need for a long cable.

[0043] In an embodiment of the present invention, the atomic force microscope may be a tuning fork-based atomic force microscope, and may be a quality factor-enhanced qPlus atomic force microscope. Alternatively, the charge amplifier circuit of the atomic force microscope may be a pre-charge amplifier circuit of a tuning fork-based atomic force microscope. In one example, the charge amplifier circuit of the atomic force microscope may be a pre-charge amplifier circuit of a quality factor-enhanced qPlus atomic force microscope.

[0044] Through the design of the charge amplifier circuit of the atomic force microscope in the embodiment of the present invention, it is possible to obtain a design function with a high signal-to-noise ratio, a compact structure, and simple production by designing the relevant devices and parameters of the charge amplifier circuit, so as to realize signal acquisition and measurement of the atomic force microscope with high resolution.

[0045] In another embodiment of the present invention, a signal acquisition device for an atomic force microscope is provided, wherein the signal acquisition device may include the charge amplification circuit of the atomic force microscope according to the aforementioned embodiment, for signal acquisition and amplification processing of the atomic force microscope.

[0046] In another embodiment of the present invention, a signal acquisition method for an atomic force microscope is provided. Figure 6 FIG. 6 is a flow chart showing a signal acquisition method 600 for an atomic force microscope according to an embodiment of the present invention. Figure 6 As shown, the 600 may include:

[0047] Step 610: Receive the AC output signal of the atomic force microscope.

[0048] Step 620: Input the AC output signal of the atomic force microscope into the charge amplifier circuit of the atomic force microscope described above to amplify the AC output signal.

[0049] In the embodiment of the present invention, the signal acquisition method of the charge amplifier circuit of the atomic force microscope of the embodiment of the present invention can be used to obtain a design function with high signal-to-noise ratio, compact structure, and simple production, so as to realize signal acquisition and measurement of high-resolution atomic force microscope.

[0050] Of course, the above-mentioned specific embodiments are merely examples and not limitations, and those skilled in the art can, based on the concept of the present invention, merge and combine some steps and devices from the various embodiments described separately above to achieve the effects of the present invention. Such merged and combined embodiments are also included in the present invention, and such merges and combinations are not described one by one here.

[0051] Note that the advantages, benefits, and effects mentioned in the present invention are merely illustrative and non-limiting, and should not be construed as necessarily possessed by each embodiment of the present invention. Furthermore, the specific details of the invention described above are provided for illustrative purposes and to facilitate understanding, and are not intended to be limiting. The details do not necessarily limit the present invention to being implemented using the specific details.

[0052] The block diagrams of the devices, apparatuses, equipment, and systems involved in the present invention are intended to be illustrative examples only and are not intended to require or imply that they must be connected, arranged, or configured in the manner shown in the block diagrams. As will be appreciated by those skilled in the art, these devices, apparatuses, equipment, and systems may be connected, arranged, or configured in any manner. Words such as "include," "comprise," "have," and the like are open-ended words, meaning "including but not limited to," and may be used interchangeably therewith. The words "or" and "and" used herein refer to the words "and / or" and may be used interchangeably therewith, unless the context clearly indicates otherwise. The word "such as" used herein refers to the phrase "such as but not limited to," and may be used interchangeably therewith.

[0053] The step flow charts and the above method descriptions in the present invention are intended to be illustrative examples only and are not intended to require or imply that the steps of the various embodiments must be performed in the order given. As will be appreciated by those skilled in the art, the order of the steps in the above embodiments can be performed in any order. Words such as "thereafter," "then," "next," and the like 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 an element in the singular, such as using the articles "a," "an," or "the," is not to be construed as limiting the element to the singular.

[0054] In addition, the steps and devices in the various embodiments of this document are not limited to being implemented in a certain embodiment. In fact, based on the concept of the present invention, relevant partial steps and partial devices in the various embodiments of this document can be combined to conceive new embodiments, and these new embodiments are also included in the scope of the present invention.

[0055] Each operation of the method described above may be performed by any suitable means capable of performing the corresponding functions, which may include various hardware and / or software components and / or modules, including but not limited to circuits, application specific integrated circuits (ASICs), or processors.

[0056] The various illustrated logic blocks, modules, and circuits described herein may be implemented or performed 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. A general-purpose processor may be a microprocessor, but as an alternative, the processor may be any commercially available processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, such as a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.

[0057] The steps of the methods or algorithms described in conjunction with the present invention may be embedded directly in hardware, in a software module executed by a processor, or in a combination of the two. A software module may reside 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, hard disks, removable disks, CD-ROMs, and the like. A storage medium may be coupled to a processor so that the processor can read information from and write information to the storage medium. In an alternative embodiment, the storage medium may be integral to the processor. A software module may be a single instruction or many instructions and may be distributed across several different code segments, between different programs, and across multiple storage media.

[0058] The methods herein include one or more actions for implementing the methods described. The methods and / or actions may be interchangeable with one another without departing from the scope of the claims. In other words, unless a specific order of actions is specified, the order and / or use of the specific actions may be modified without departing from the scope of the claims.

[0059] The functions described can be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions can be stored as one or more instructions on a tangible computer-readable medium. The storage medium can be any available tangible medium that can be accessed by a computer. By way of example and not limitation, such computer-readable media can 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 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.

[0060] Thus, a computer program product can perform the operations described herein. For example, such a computer program product can be a computer-readable tangible medium having instructions tangibly stored (and / or encoded) thereon, the instructions being executable by one or more processors to perform the operations described herein. The computer program product can include packaging materials.

[0061] Software or instructions may also be transmitted over a transmission medium. For example, the software may be transmitted 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.

[0062] Furthermore, modules and / or other appropriate means for performing the methods and techniques described herein can be downloaded and / or otherwise obtained by user terminals and / or base stations, as appropriate. For example, such a device can be coupled to a server to facilitate the transmission of the means for performing the methods described herein. Alternatively, the various methods described herein can be provided via a storage component (e.g., RAM, ROM, or a physical storage medium such as a CD or floppy disk) so that the user terminal and / or base station can obtain the various methods when coupled to the device or provided with the storage component. Furthermore, any other appropriate technology for providing the methods and techniques described herein to a device can be utilized.

[0063] Other examples and implementations are within the scope and spirit of the 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 of these. Features that implement the functions can also be physically located in various locations, including being distributed so that parts of the functions are implemented at different physical locations. Moreover, as used herein, including in the claims, “or” used in a list of items beginning with “at least one of” indicates a separate list, so that, for example, a list 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). Furthermore, the word “exemplary” does not mean that the example described is preferred or better than other examples.

[0064] Various changes, substitutions, and modifications may be made to the technology described herein without departing from the teachings as defined by the appended claims. Moreover, the scope of the claims is not limited to the specific aspects of the processes, machines, manufacture, compositions of things, means, methods, and actions described above. Currently existing or later developed processes, machines, manufacture, compositions of things, means, methods, or actions that perform substantially the same function or achieve substantially the same results as the corresponding aspects described herein may be utilized. Accordingly, the appended claims include within their scope such processes, machines, manufacture, compositions of things, means, methods, or actions.

[0065] The above description of the invented aspects is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these aspects will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other aspects without departing from the scope of the present invention. Therefore, the present invention is not intended to be limited to the aspects shown herein, but rather to be accorded the widest scope consistent with the principles and novel features of the invention herein.

[0066] The above description has been presented for purposes of illustration and description. Furthermore, this description is not intended to limit the embodiments of the present invention to the forms invented herein. Although a number of example aspects and embodiments have been discussed above, those skilled in the art will recognize certain variations, modifications, alterations, additions, and sub-combinations thereof.

Claims

1. A charge amplifier circuit for an atomic force microscope, wherein: The charge amplifier circuit receives the AC output signal of the atomic force microscope, and the bandwidth of the charge amplifier circuit is 150 Hz-250 kHz. The charge amplifier circuit includes: a first-stage charge amplifier, wherein a gain of the first-stage charge amplifier is associated with a first feedback capacitor of the first-stage charge amplifier, and an amplification factor of the first-stage charge amplifier is -1 V / pC; and a second-stage voltage amplifier, wherein the input terminal of the second-stage voltage amplifier is connected to the output terminal of the first-stage charge amplifier, the gain of the second-stage voltage amplifier is associated with the second feedback resistor of the second-stage voltage amplifier, the amplification factor of the second-stage voltage amplifier is -1, and the amplification factor of the charge amplifier circuit is 1 V / pC; Wherein, the second-stage voltage amplifier includes: a second input unit, the second input unit including a third input resistor, an input end of the second input unit receiving the voltage signal output by the first-stage charge amplifier, and an output end of the second input unit being respectively connected to the input end of the second feedback unit and the inverting input end of the second amplification unit; a second feedback unit, the second feedback unit comprising a second feedback resistor and a second feedback capacitor connected in parallel, the output end of the second feedback unit being connected to the output end of the second amplifying unit; The second amplifying unit is a voltage-type operational amplifier, the non-inverting input terminal of the voltage-type operational amplifier is grounded via a second amplifying resistor, and the output terminal of the voltage-type operational amplifier is connected to the output resistor as the output terminal of the second-stage voltage amplifier.

2. The charge amplifier circuit according to claim 1, wherein: The first-stage charge amplifier includes: a first input unit, the first input unit comprising a first input resistor, a first input capacitor, and a second input resistor connected in sequence, an input end of the first input unit receiving an AC output signal of the atomic force microscope, and an output end of the first input unit being connected to an input end of a first feedback unit and an inverting input end of a first amplifying unit, respectively; a first feedback unit, the first feedback unit comprising a first feedback resistor and a first feedback capacitor connected in parallel, an output end of the first feedback unit being connected to an output end of the first amplifying unit; The first amplifying unit is an inverting amplifier, wherein the non-inverting input terminal of the inverting amplifier is grounded via a first amplifying 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.

3. The charge amplifier 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 to isolate the load circuit and / or to adjust the gain of the charge amplifier circuit.

4. The charge amplifier circuit according to claim 2, wherein: The inverting amplifier comprises 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 first amplifying unit input; 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 limit 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 amplifier circuit according to claim 1, wherein: The bandwidth of the charge amplifier circuit is 15 kHz-30 kHz.

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

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

8. The charge amplifier circuit according to claim 7, wherein: The charge amplifier circuit of the atomic force microscope is a pre-charge amplifier 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 a charge amplification circuit of the atomic force microscope according to any one of claims 1 to 8.

10. A signal acquisition method for an atomic force microscope, comprising: receiving an AC output signal of the atomic force microscope; The AC output signal of the atomic force microscope is input into the charge amplifier circuit of the atomic force microscope according to any one of claims 1 to 8, so as to amplify the AC output signal.

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