A single molecule thermal conductivity signal differential amplification adjustable gain detection system

Abstract

The present application relates to a kind of single molecule thermal conductivity signal differential amplification adjustable gain detection system, the differential amplification adjustable gain detection system includes first amplification module, second amplification module, differential amplification module;The first amplification module is used to receive the chip thermal excitation thermal conductivity current signal, the first amplification module includes true logarithm amplification circuit, first low-pass filter circuit, first instrument amplification circuit connected along signal direction, the second amplification module is used to receive the excitation signal, the second amplification module includes second low-pass filter circuit, second instrument amplification circuit connected along signal direction;The differential amplification module connects the first amplification module, second amplification module, the differential amplification module is used to receive the output signal of the first amplification module, the output signal of the second amplification module, differential amplification is carried out, to extract from the output signal of the single molecule chip device Signal containing single molecule thermal conductivity ac signal.

Description

Technical Field

[0001] This invention relates to the field of gain detection systems, specifically to a differential amplification adjustable gain detection system for single-molecule thermal conductivity signals. Background Technology

[0002] Research on heat transport at the nanoscale is crucial for the development of novel nanoelectronic devices, especially for studying heat transport in single molecules. Understanding the laws governing charge and energy transport at the atomic and molecular scale, represented by molecular junctions, is fundamentally important and holds promise for revealing quantum phenomena without classical analogues. In the context of nanoscale devices, atomic-level metal contacts and single-molecule junctions represent the ultimate limit of miniaturization and have become exemplary systems for revealing previously unknown quantum effects related to charge and energy transport.

[0003] However, studying heat transport at the nanoscale remains a formidable challenge, and it has so far been difficult to capture or detect. Although the thermal conductivity of single-molecule junctions can be measured using picometric scanning calorimetry probes with picowatt resolution, there is still a long way to go in accurately measuring and characterizing heat transport, dissipation, and transfer within these junctions. Designing such a detection circuit and an efficient and stable signal detection device is crucial. For single-molecule thermal conductivity signal detection, noise, vibration, and other interferences are among the factors affecting detection accuracy. Furthermore, the measurement range of single-molecule thermal conductivity signals is very large, spanning from milliamperes to picoamperes, and when the signal is weak, down to the picoampere level, it is difficult to extract, which is also one of the challenges in circuit design. Currently, there are no similar advanced circuit devices that can be directly used. Therefore, a new detection circuit needs to be proposed to meet the requirements of high accuracy, high stability, low noise, large measurement range, and adjustable gain in single-molecule thermal conductivity signal detection.

[0004] The purpose of this invention is to design a differential amplification and adjustable gain detection system for single-molecule thermal conductivity signals to address the problems existing in the prior art. Summary of the Invention

[0005] To address the problems existing in the prior art, the present invention provides a differential amplification adjustable gain detection system for single-molecule thermal conductivity signals, which can effectively solve at least one of the problems existing in the prior art.

[0006] The technical solution of this invention is:

[0007] A differential amplification adjustable gain detection system for single-molecule thermal conductivity signals is used to connect to a single-molecule chip device and amplify the output signal of the single-molecule chip device. The output signal of the single-molecule chip device includes a chip thermal excitation thermal conductivity current signal and an excitation signal. The differential amplification adjustable gain detection system includes a first amplification module, a second amplification module, and a differential amplification module.

[0008] The first amplification module is used to receive the thermally excited thermal current signal of the chip. The first amplification module includes a true logarithmic amplifier circuit, a first low-pass filter circuit, and a first instrument amplification circuit connected in sequence according to the signal path. The input terminal of the true logarithmic amplifier circuit is connected to the thermally excited thermal current signal of the chip. The true logarithmic amplifier circuit performs logarithmic amplification on the thermally excited thermal current signal of the chip. The first low-pass filter circuit performs low-pass filtering on the output signal of the true logarithmic amplifier circuit. The first instrument amplification circuit performs instrument amplification on the output signal of the first low-pass filter circuit.

[0009] The second amplification module is used to receive the excitation signal. The second amplification module includes a second low-pass filter circuit and a second instrument amplification circuit connected in sequence according to the signal direction. The second low-pass filter circuit performs low-pass filtering on the excitation signal, and the second instrument amplification circuit amplifies the output signal of the second low-pass filter circuit.

[0010] The differential amplifier module is connected to the first amplifier module and the second amplifier module. The differential amplifier module is used to receive the output signal of the first amplifier module and the output signal of the second amplifier module. The differential amplifier module includes a third low-pass filter circuit and a differential amplifier circuit connected in sequence according to the signal direction. The third low-pass filter circuit performs low-pass filtering on the output signal of the first amplifier module and the output signal of the second amplifier module. The differential amplifier circuit differentially amplifies the output signal of the third low-pass filter circuit, thereby extracting a signal containing a single-molecule thermal conductivity AC signal from the output signal of the single-molecule chip device.

[0011] Furthermore, the chip thermal excitation thermal conductivity current signal includes a positive chip thermal excitation signal and a negative chip thermal excitation signal. The true logarithmic amplifier circuit includes an amplifier U2, which operates in a non-inverting amplification state. The positive terminal of the amplifier U2 is used to receive the positive chip thermal excitation signal, and the negative terminal of the amplifier U2 is used to receive the negative chip thermal excitation signal. A transistor Q1 is connected between the negative terminal and the output terminal of the amplifier U2. The base and collector of the transistor Q1 are connected to the negative terminal of the amplifier U2, and the emitter of the transistor Q1 is connected to the output terminal of the amplifier U2. The logarithmic characteristics of the transistor Q1 in the saturation region are used to logarithmically amplify the chip thermal excitation thermal conductivity current signal.

[0012] Furthermore, the true logarithmic amplifier circuit includes amplifier U1 and amplifier U3;

[0013] The amplifier U1 operates in a non-inverting amplification state. The positive terminal of the amplifier U1 is grounded, and the negative terminal of the amplifier U1 is used to receive a reference signal. A transistor Q2 is connected between the negative terminal and the output terminal of the amplifier U1. The base and collector of the transistor Q2 are connected to the negative terminal of the amplifier U1, and the emitter of the transistor Q2 is connected to the output terminal of the amplifier U1. The reference signal is logarithmically amplified by utilizing the logarithmic characteristic of the transistor Q2 in the saturation region.

[0014] The amplifier U3 operates in subtractor mode. The positive terminal of the amplifier U3 is connected to the output signal of the amplifier U1, and the negative terminal of the amplifier U3 is connected to the output signal of the amplifier U2. The amplifier U3 performs a logarithmic subtraction between the output signal of the amplifier U2 and the output signal of the amplifier U1, thereby shifting the output signal of the amplifier U2.

[0015] Furthermore, the true logarithmic amplifier circuit includes amplifier U4.

[0016] The amplifier U4 operates in directional amplification mode. The positive terminal of the amplifier U4 is grounded, and the negative terminal of the amplifier U4 is connected to the output signal of the amplifier U3 to amplify the output signal of the amplifier U3 in reverse.

[0017] Furthermore, the first low-pass filter circuit, the second low-pass filter circuit, and the third low-pass filter circuit are all RC low-pass filters. Adjusting the value of the resistor or capacitor can change the cutoff frequency of the corresponding low-pass filter. The chip thermally excited thermal conductivity current signal includes the chip intrinsic positive signal and the chip intrinsic negative signal.

[0018] The first low-pass filter circuit includes a resistor R11 connected in series with the output terminal of the true logarithmic amplifier circuit, a resistor R12 connected in series with the ground terminal, a capacitor C8 connected in parallel with the resistor R11, a capacitor C7 connected in parallel with the resistor R12, and a capacitor C9 connected in parallel between the resistor R11 and the resistor R12.

[0019] The second low-pass filter circuit includes R14 connected in series with the intrinsic positive signal of the chip, R15 connected in series with the intrinsic negative signal of the chip, C11 connected in parallel with the resistor R14, C10 connected in parallel with the resistor R15, and C12 connected in parallel between the resistor R14 and the resistor R15.

[0020] The third low-pass filter circuit includes R13 connected in series with the output terminal of the first amplification module, R16 connected in series with the output terminal of the second amplification module, C14 connected in parallel with the resistor R13, C113 connected in parallel with the resistor R16, and C15 connected in parallel between the resistor R13 and the resistor R16.

[0021] Furthermore, the first instrument amplification circuit includes an instrument amplifier A1, which operates in an amplification state. The positive terminal of the instrument amplifier A1 is connected to the output signal of the first low-pass filter circuit to amplify the output signal of the first low-pass filter circuit. The instrument amplifier A1 is connected to a gain setting resistor RG1, and adjusting the resistance value of the gain setting resistor RG1 can change the gain of the instrument amplifier A1.

[0022] The second instrument amplification circuit includes an instrument amplifier A2, which operates in an amplification state. The positive and negative terminals of the instrument amplifier A2 are respectively connected to the output signal of the second low-pass filter circuit to amplify the output signal of the second low-pass filter circuit. The instrument amplifier A2 is connected to a gain setting resistor RG2, and adjusting the resistance value of the gain setting resistor RG2 can change the gain of the instrument amplifier A2.

[0023] Furthermore, the differential amplifier module includes an instrumentation amplifier A3, which operates in differential amplification mode. The positive and negative terminals of the instrumentation amplifier A3 are respectively connected to the output signal of the third low-pass filter circuit, and the instrumentation amplifier A3 differentially amplifies the two output signals of the third low-pass filter circuit.

[0024] Furthermore, the instrument amplifier A3 is connected to a gain setting resistor RG3, and adjusting the resistance value of the gain setting resistor RG3 can change the gain of the instrument amplifier A3.

[0025] Furthermore, the output of the differential amplifier module is connected to a filter to detect the single-molecule thermal conductivity AC signals at different frequencies.

[0026] Furthermore, the filter includes an amplifier UF, the positive terminal of which is connected to the output signal of the differential amplification module. The amplifier UF operates in filter mode, and the positive terminal of the amplifier UF is connected in series with resistors R1 and R2. Adjusting the resistance values ​​of resistors R1 and / or R2 can change the filtering bandwidth of the amplifier UF, thereby enabling the detection of the single-molecule thermal conductivity AC signal at different frequencies.

[0027] Therefore, the present invention provides the following effects and / or advantages:

[0028] This application uses a first amplification module, a second amplification module, a differential amplification module, and their interconnections to input single-molecule thermal conduction signals generated at different ports of four single-molecule chip devices. The weak single-molecule thermal conduction signals are then initially amplified by a true logarithmic amplifier module, logarithmically converted, and sent to the next stage instrumentation amplifier. Next, three passive low-pass filter modules (first low-pass filter circuit, second low-pass filter circuit, and third low-pass filter circuit) and a second-order active low-pass filter (filter) are used to filter the input amplifier signal, thereby improving signal stability. Finally, a differential amplifier module composed of the three instrumentation amplifiers differentially divides the initially amplified thermal conduction signal, converting the thermally excited current signal from the chip into a voltage signal, and then differentially dividing it with the excitation signal to measure the thermal conduction signal, extracting the weak heat flow of the single molecules excited by the temperature difference, and ultimately measuring the single-molecule thermal conduction.

[0029] This application uses a simple circuit with a clear circuit structure and well-defined functions, requiring fewer circuit components, to extract AC signals containing single-molecule thermal conductivity from the output signal of the single-molecule chip device.

[0030] It should be understood that the above summary and the following detailed description of the invention are exemplary and explanatory, and are intended to provide further explanation of the invention as claimed. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of a module according to one embodiment of the present invention.

[0032] Figure 2 This is a circuit diagram of a true logarithmic amplifier circuit according to one embodiment of the present invention.

[0033] Figure 3 This is one embodiment of the present invention. Figure 1 A circuit diagram excluding the true logarithmic amplifier circuit.

[0034] Figure 4 The output curves of amplifiers U3 and U4 are shown in one embodiment of the present invention.

[0035] Figure 5 This is the output curve of the differential amplifier module in one embodiment of the present invention.

[0036] Figure 6 This is a calibration diagram of the temperature resistivity of the system provided by the present invention.

[0037] Figure 7 The current I of the input signal of the system provided by the present invention 3 The relationship between the voltage V of the output signal and the output signal.

[0038] Figure 8 The test diagram shows the bandwidth of the system provided by this invention, which is 0-100Hz.

[0039] Figure 9 A graph showing the relationship between the input current and output voltage of the system provided by this invention.

[0040] Figure 10 The theoretical waveform and actual test waveform diagram of the system provided by this invention. Detailed Implementation

[0041] To facilitate understanding by those skilled in the art, the structure of the present invention will now be described in further detail with reference to the accompanying drawings:

[0042] refer to Figure 1 A differential amplification adjustable gain detection system for single-molecule thermal conductivity signals is used to connect to a single-molecule chip device and amplify the output signal of the single-molecule chip device. The output signal of the single-molecule chip device includes a chip thermal excitation thermal conductivity current signal and an excitation signal. The differential amplification adjustable gain detection system includes a first amplification module, a second amplification module, and a differential amplification module.

[0043] In this embodiment, the single-molecule chip device is existing technology, and the detection of single-molecule thermal conductivity signals using a single-molecule chip device is also existing technology. For example, in "Resistance thermometry-based picowatt-resolution heat-flow calorimeter" (Appl. Phys. Lett. 102, 163110 (2013), S.Sadat 1 , E. Meyhofer 1，a) and P.Reddy 1，2，b) ), "Room temperature picowatt-resolution calorimetry" (Appl.Phys.Lett.99, 043106 (2011), Seid Sadat , YiJie Chua , Woochu l Lee , Yashar Ganjeh , Katsuo Kurabayash i, Edgar Meyhofer a) and Pramod Reddy a)The measurement instrument setup requires measuring several important physical quantities: temperature coefficient of resistance (TCR), cutoff frequency, and chip thermal conductivity. These measurements must be performed in a vacuum environment, powered by a constant alternating current, and using a lock-in amplifier for signal acquisition. Furthermore, the chip thermally excited thermal conductivity current signal refers to the signal generated by the transition of bandgap electrons due to the thermal energy produced by atomic vibrations in the semiconductor crystal.

[0044] refer to Figure 1 The first amplification module is used to receive the thermally excited thermal current signal of the chip. The first amplification module includes a true logarithmic amplifier circuit, a first low-pass filter circuit, and a first instrument amplification circuit connected in sequence according to the signal direction. The input terminal of the true logarithmic amplifier circuit is connected to the thermally excited thermal current signal of the chip. The true logarithmic amplifier circuit performs logarithmic amplification on the thermally excited thermal current signal of the chip. The first low-pass filter circuit performs low-pass filtering on the output signal of the true logarithmic amplifier circuit. The first instrument amplification circuit performs instrument amplification on the output signal of the first low-pass filter circuit.

[0045] Specifically, the chip thermal excitation thermal conductivity current signal includes a positive chip thermal excitation signal and a negative chip thermal excitation signal, referenced... Figure 2 The true logarithmic amplifier circuit includes an amplifier U2, which operates in a non-inverting amplification state. The positive terminal of the amplifier U2 is used to receive the positive signal of the chip's thermal excitation, and the negative terminal of the amplifier U2 is used to receive the negative signal of the chip's thermal excitation. A transistor Q1 is connected between the negative terminal and the output terminal of the amplifier U2. The base and collector of the transistor Q1 are connected to the negative terminal of the amplifier U2, and the emitter of the transistor Q1 is connected to the output terminal of the amplifier U2. The logarithmic characteristics of the transistor Q1 in the saturation region are used to logarithmically amplify the thermal current signal of the chip's thermal excitation.

[0046] In this embodiment, the amplifier operates in a unidirectional amplification state, which is existing technology. The specific connection circuit of amplifier U2 can be found in [reference needed]. Figure 2The output of the amplifier has a linear relationship with its input. In this embodiment, a transistor Q1 is connected between the negative terminal and the output terminal of the amplifier U2. Because the output and input of the amplifier have a linear amplification relationship, and transistor Q1 is connected between the negative terminal and the output terminal, and the thermal current signal generated by the chip is very weak, transistor Q1 operates in the saturation region before the amplification region. At this time, the output voltage of the transistor has a logarithmic amplification relationship. Under the linear amplification relationship of amplifier U2, the true logarithmic amplifier circuit composed of amplifier U2 and transistor Q1 can achieve a combination of logarithmic and linear amplification. A significant feature of a true logarithmic amplifier is that the transistor has logarithmic characteristics when the signal is small, which makes the input and output signals logarithmically related, thus giving the circuit good amplification capability for small signals.

[0047] Furthermore, the true logarithmic amplifier circuit includes amplifier U1 and amplifier U3;

[0048] The amplifier U1 operates in a non-inverting amplification state. The positive terminal of the amplifier U1 is grounded, and the negative terminal of the amplifier U1 is used to receive a reference signal. A transistor Q2 is connected between the negative terminal and the output terminal of the amplifier U1. The base and collector of the transistor Q2 are connected to the negative terminal of the amplifier U1, and the emitter of the transistor Q2 is connected to the output terminal of the amplifier U1. The reference signal is logarithmically amplified by utilizing the logarithmic characteristic of the transistor Q2 in the saturation region.

[0049] The amplifier U3 operates in subtractor mode. The positive terminal of the amplifier U3 is connected to the output signal of the amplifier U1, and the negative terminal of the amplifier U3 is connected to the output signal of the amplifier U2. The amplifier U3 performs a logarithmic subtraction between the output signal of the amplifier U2 and the output signal of the amplifier U1, thereby shifting the output signal of the amplifier U2.

[0050] In this embodiment, the working principle of amplifier U1 is the same as that of amplifier U2. The specific connection circuit of amplifier U1 can be found in [reference needed]. Figure 2 .

[0051] Amplifiers U2 and U1 amplify and output their respective signals. Then, the output signals of amplifiers U2 and U1 are connected to the input of amplifier U3. The amplifier operating in subtractor mode is existing technology; the specific connection circuit can be found in [reference needed]. Figure 2 At this point, amplifier U3 subtracts the output signals of amplifiers U2 and U1, referencing... Figure 3VU2 is the output characteristic curve of amplifier U2, and VU3 is the output characteristic curve of amplifier U3. Since both amplifiers U2 and U1 are in logarithmic amplification mode, and both amplifiers U2 and U3 use transistors, the amplification base of the logarithmic amplification of amplifiers U2 and U3 is the same. Amplifier U3 subtracts the output signals of amplifiers U2 and U1, and according to the logarithmic operation formula, the base VU2 is shifted down to obtain VU3. The purpose of this is that the output voltage of amplifier U2 may exceed the amplification range of subsequent amplifier circuits, so its curve is shifted down in this circuit in advance to meet the amplification range of subsequent amplifier circuits.

[0052] Furthermore, the true logarithmic amplifier circuit includes amplifier U4.

[0053] The amplifier U4 operates in directional amplification mode. The positive terminal of the amplifier U4 is grounded, and the negative terminal of the amplifier U4 is connected to the output signal of the amplifier U3 to amplify the output signal of the amplifier U3 in reverse.

[0054] In the above, subtraction in amplifier U3 shifts the output voltage of amplifier U2 downwards, thus satisfying the amplification range of amplifier U4. (Reference) Figure 2 In this embodiment, amplifier U4 is in amplification mode, thereby further amplifying the down-shifted signal output from lower amplifier U2 to obtain the signal shown below. Figure 3 The VU4 curve shown.

[0055] Next, the signal output from amplifier U4 is filtered and then sent to the first instrument amplification circuit for instrument amplification.

[0056] The first instrument amplification circuit includes an instrument amplifier A1, which operates in an amplification state. The positive and negative terminals of the instrument amplifier A1 are respectively connected to the output signal of the first low-pass filter circuit to amplify the output signal of the first low-pass filter circuit. The instrument amplifier A1 is connected to a gain setting resistor RG1, and adjusting the resistance value of the gain setting resistor RG1 can change the gain of the instrument amplifier A1.

[0057] In this embodiment, the instrumentation amplifier operating in amplification mode is a prior art technique, and its connection method is as follows: Figure 4 As shown. Adjusting the value of resistor RG1 allows for different gain levels.

[0058] Next, we will introduce the processing of the other output signal of the single-molecule chip device.

[0059] The second amplification module is used to receive the excitation signal. The second amplification module includes a second low-pass filter circuit and a second instrument amplification circuit connected in sequence according to the signal direction. The second low-pass filter circuit performs low-pass filtering on the excitation signal, and the second instrument amplification circuit amplifies the output signal of the second low-pass filter circuit.

[0060] refer to Figure 4 Specifically, the second instrument amplification circuit includes an instrument amplifier A2, which operates in an amplification state. The positive terminal of the instrument amplifier A2 is connected to the output signal of the second low-pass filter circuit to amplify the output signal of the second low-pass filter circuit. The instrument amplifier A2 is connected to a gain setting resistor RG2, and adjusting the resistance value of the gain setting resistor RG2 can change the gain of the instrument amplifier A2.

[0061] The two instrument amplifiers in the first and second instrument amplifier circuits can be gain-adjusted to meet the amplification requirements of signals with different input ranges.

[0062] After introducing the two amplification modules, we will explain how to further process the two amplified signals obtained from the single-molecule chip device.

[0063] The differential amplifier module is connected to the first amplifier module and the second amplifier module. The differential amplifier module is used to receive the output signal of the first amplifier module and the output signal of the second amplifier module. The differential amplifier module includes a third low-pass filter circuit and a differential amplifier circuit connected in sequence according to the signal direction. The third low-pass filter circuit performs low-pass filtering on the output signal of the first amplifier module and the output signal of the second amplifier module. The differential amplifier circuit differentially amplifies the output signal of the third low-pass filter circuit, thereby extracting a signal containing a single-molecule thermal conductivity AC signal from the output signal of the single-molecule chip device.

[0064] Specifically, refer to Figure 4 The differential amplifier module includes an instrument amplifier A3, which operates in differential amplification mode. The positive and negative terminals of the instrument amplifier A3 are respectively connected to the output signal of the third low-pass filter circuit, and the instrument amplifier A3 differentially amplifies the two output signals of the third low-pass filter circuit.

[0065] Furthermore, the instrument amplifier A3 is connected to a gain setting resistor RG3, and adjusting the resistance value of the gain setting resistor RG3 can change the gain of the instrument amplifier A3.

[0066] Differential amplifiers possess the characteristic of circuit symmetry, which helps stabilize the operating point. Utilizing the symmetry of circuit parameters and negative feedback, differential amplifiers effectively stabilize the quiescent operating point, with a significant feature being the amplification of differential-mode signals and suppression of common-mode signals. This embodiment uses a differential amplifier module to amplify the signal differentially, and the output signal is the difference in amplitude between the two input signals of the differential amplifier module. (Reference) Figure 5 VA1 is the output curve of amplifier A1, and its amplitude can be changed by adjusting the gain of amplifier A1; VA2 is the output curve of amplifier A2, and its amplitude can be changed by adjusting the gain of amplifier A2; VA3-1 is the output curve of amplifier A3, which is obtained by differentially dividing signals VA1 and VA2; VA3-2 is the output curve of amplifier A3 after adjusting the gain of amplifier A3.

[0067] Through the aforementioned circuitry and its connections, single-molecule thermal conduction signals generated at different ports of four single-molecule chip devices are input. These signals are then initially amplified by a true logarithmic amplifier module, logarithmically converted, and then fed into the next stage instrumentation amplifier. Next, three passive low-pass filter modules (first, second, and third low-pass filter circuits) and a second-order active low-pass filter (filter) are used to filter the input amplifier signal, thereby improving signal stability. Finally, a differential amplifier module composed of the three instrumentation amplifiers differentially divides the initially amplified thermal conduction signal, converting the thermally excited current signal from the chip into a voltage signal, and then differentially dividing it with the excitation signal to measure the thermal conduction signal. This extracts the weak heat flow of the single molecule excited by the temperature difference, ultimately measuring the single-molecule thermal conduction.

[0068] Further, refer to Figure 4 The first low-pass filter circuit, the second low-pass filter circuit, and the third low-pass filter circuit are all RC low-pass filters. Adjusting the value of the resistor or capacitor can change the cutoff frequency of the corresponding low-pass filter. The chip thermally excited thermal conductivity current signal includes the chip intrinsic positive signal and the chip intrinsic negative signal.

[0069] The first low-pass filter circuit includes a resistor R11 connected in series with the output terminal of the true logarithmic amplifier circuit, a resistor R12 connected in series with the ground terminal, a capacitor C8 connected in parallel with the resistor R11, a capacitor C7 connected in parallel with the resistor R12, and a capacitor C9 connected in parallel between the resistor R11 and the resistor R12.

[0070] The second low-pass filter circuit includes R14 connected in series with the intrinsic positive signal of the chip, R15 connected in series with the intrinsic negative signal of the chip, C11 connected in parallel with the resistor R14, C10 connected in parallel with the resistor R15, and C12 connected in parallel between the resistor R14 and the resistor R15.

[0071] The third low-pass filter circuit includes R13 connected in series with the output terminal of the first amplification module, R16 connected in series with the output terminal of the second amplification module, C14 connected in parallel with the resistor R13, C113 connected in parallel with the resistor R16, and C15 connected in parallel between the resistor R13 and the resistor R16.

[0072] In this embodiment, the first, second, and third low-pass filter circuits are all passive low-pass filters. Furthermore, each of these circuits has an adjustable cutoff frequency between 0 and 20kHz, adjustable by the values ​​of the resistors or capacitors within each circuit. Preferably, the bandwidths of the first and second low-pass filter circuits are greater than or equal to the bandwidth of the third low-pass filter circuit. This ensures that during the filtering process, the first and second low-pass filter circuits allow the signal to pass through as much as possible, while the third low-pass filter circuit minimizes its bandwidth, thereby improving signal quality and reducing noise interference.

[0073] Furthermore, the output of the differential amplifier module is connected to a filter to detect the single-molecule thermal conductivity AC signals at different frequencies.

[0074] Furthermore, the filter includes an amplifier UF, the positive terminal of which is connected to the output signal of the differential amplification module. The amplifier UF operates in filter mode, and the positive terminal of the amplifier UF is connected in series with resistors R1 and R2. Adjusting the resistance values ​​of resistors R1 and / or R2 can change the filtering bandwidth of the amplifier UF, thereby enabling the detection of the single-molecule thermal conductivity AC signal at different frequencies.

[0075] In this embodiment, the signal output from amplifier A3 is filtered using a filter. The signal output from A3 is filtered and its amplitude stabilized by an active second-order low-pass filter UF. The values ​​of R1 and R2 can also be adjusted to change the filter bandwidth, thereby enabling the detection of signals at different frequencies and achieving stable signal output while minimizing signal noise interference.

[0076] Experimental data

[0077] Figure 6 This is a calibration graph of the system for temperature resistivity, where TCR represents temperature resistivity. This graph reflects the system's calibration of the chip parameters. Knowing the TCR curve, this system can calculate the temperature given the known resistance, with the error controlled within 3%.

[0078] Figure 7 The current I of the system's input signal 3The graph shows the relationship between the voltage V of the output signal and the linear fitting result. The left graph shows the result obtained by linear fitting. The better the linearity of the fitting result, the more stable the amplifier is and the better the measurement effect.

[0079] Figure 8 The test graph shows that the system provided in this application has a good low-pass filtering effect, which ensures the accuracy of the thermal conductivity signal.

[0080] Figure 9 The left figure shows the relationship between the system input current and output voltage, illustrating that the amplifier provided in this application has a wide test range and can be applied to input currents from 0.01uA to 100uA. The right figure shows the relationship between the system input current and output voltage in differential amplification mode, illustrating that the system has good amplification and linearity in differential mode.

[0081] Figure 10 The figures show the theoretical and actual test waveforms of the system. It can be seen that the theoretical waveform and the actual test waveform are the same, indicating that the differential amplification scheme for the thermal conductivity signal of this system is correct.

[0082] It should be noted that any reference signs placed between parentheses in the claims should not be construed as limiting the claims. The word "comprising" does not exclude the presence of components or steps not listed in the claims. The word "a" or "an" preceding a component does not exclude the presence of a plurality of such components. The invention can be implemented by means of hardware comprising several different components and by means of a suitably programmed computer. In a unit claim enumerating several means, several of these means may be embodied by the same item of hardware. The use of the words first, second, and third, etc., does not indicate any order. These words can be interpreted as names.

[0083] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0084] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0085] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms should not be construed as necessarily referring to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

Claims

1. A differential amplification and adjustable gain detection system for single-molecule thermal conductivity signals, characterized in that: The differential amplification adjustable gain detection system is used to connect to a single-molecule chip device and amplify the output signal of the single-molecule chip device. The output signal of the single-molecule chip device includes a chip thermal excitation thermal conductivity current signal and an excitation signal. The differential amplification adjustable gain detection system includes a first amplification module, a second amplification module, and a differential amplification module. The first amplification module is used to receive the thermally excited thermal current signal of the chip. The first amplification module includes a true logarithmic amplifier circuit, a first low-pass filter circuit, and a first instrument amplification circuit connected in sequence according to the signal path. The input terminal of the true logarithmic amplifier circuit is connected to the thermally excited thermal current signal of the chip. The true logarithmic amplifier circuit performs logarithmic amplification on the thermally excited thermal current signal of the chip. The first low-pass filter circuit performs low-pass filtering on the output signal of the true logarithmic amplifier circuit. The first instrument amplification circuit performs instrument amplification on the output signal of the first low-pass filter circuit. The second amplification module is used to receive the excitation signal. The second amplification module includes a second low-pass filter circuit and a second instrument amplification circuit connected in sequence according to the signal direction. The second low-pass filter circuit performs low-pass filtering on the excitation signal, and the second instrument amplification circuit amplifies the output signal of the second low-pass filter circuit. The differential amplifier module is connected to the first amplifier module and the second amplifier module. The differential amplifier module is used to receive the output signal of the first amplifier module and the output signal of the second amplifier module. The differential amplifier module includes a third low-pass filter circuit and a differential amplifier circuit connected in sequence according to the signal direction. The third low-pass filter circuit performs low-pass filtering on the output signal of the first amplifier module and the output signal of the second amplifier module. The differential amplifier circuit differentially amplifies the output signal of the third low-pass filter circuit, thereby extracting a signal containing a single-molecule thermal conductivity AC signal from the output signal of the single-molecule chip device.

2. The single-molecule thermal conductivity signal differential amplification adjustable gain detection system according to claim 1, characterized in that: The chip thermal excitation thermal current signal includes a positive chip thermal excitation signal and a negative chip thermal excitation signal. The true logarithmic amplifier circuit includes an amplifier U2, which operates in a non-inverting amplification state. The positive terminal of the amplifier U2 is used to receive the positive chip thermal excitation signal, and the negative terminal of the amplifier U2 is used to receive the negative chip thermal excitation signal. A transistor Q1 is connected between the negative terminal and the output terminal of the amplifier U2. The base and collector of the transistor Q1 are connected to the negative terminal of the amplifier U2, and the emitter of the transistor Q1 is connected to the output terminal of the amplifier U2. The logarithmic characteristic of the transistor Q1 in the saturation region is used to logarithmically amplify the chip thermal excitation thermal current signal.

3. The differential amplification and adjustable gain detection system for single-molecule thermal conductivity signals according to claim 2, characterized in that: The true logarithmic amplifier circuit includes amplifier U1 and amplifier U3; The amplifier U1 operates in a non-inverting amplification state. The positive terminal of the amplifier U1 is grounded, and the negative terminal of the amplifier U1 is used to receive a reference signal. A transistor Q2 is connected between the negative terminal and the output terminal of the amplifier U1. The base and collector of the transistor Q2 are connected to the negative terminal of the amplifier U1, and the emitter of the transistor Q2 is connected to the output terminal of the amplifier U1. The reference signal is logarithmically amplified by utilizing the logarithmic characteristic of the transistor Q2 in the saturation region. The amplifier U3 operates in subtractor mode. The positive terminal of the amplifier U3 is connected to the output signal of the amplifier U1, and the negative terminal of the amplifier U3 is connected to the output signal of the amplifier U2. The amplifier U3 performs a logarithmic subtraction between the output signal of the amplifier U2 and the output signal of the amplifier U1, thereby shifting the output signal of the amplifier U2.

4. The differential amplification and adjustable gain detection system for single-molecule thermal conductivity signals according to claim 3, characterized in that: The true logarithmic amplifier circuit includes amplifier U4. The amplifier U4 operates in directional amplification mode. The positive terminal of the amplifier U4 is grounded, and the negative terminal of the amplifier U4 is connected to the output signal of the amplifier U3 to amplify the output signal of the amplifier U3 in reverse.

5. The differential amplification and adjustable gain detection system for single-molecule thermal conductivity signals according to claim 1, characterized in that: The first low-pass filter circuit, the second low-pass filter circuit, and the third low-pass filter circuit are all RC low-pass filters. Adjusting the value of the resistor or capacitor can change the cutoff frequency of the corresponding low-pass filter. The chip thermally excited thermal conductivity current signal includes the chip intrinsic positive signal and the chip intrinsic negative signal. The first low-pass filter circuit includes a resistor R11 connected in series with the output terminal of the true logarithmic amplifier circuit, a resistor R12 connected in series with the ground terminal, a capacitor C8 connected in parallel with the resistor R11, a capacitor C7 connected in parallel with the resistor R12, and a capacitor C9 connected in parallel between the resistor R11 and the resistor R12. The second low-pass filter circuit includes R14 connected in series with the intrinsic positive signal of the chip, R15 connected in series with the intrinsic negative signal of the chip, C11 connected in parallel with the resistor R14, C10 connected in parallel with the resistor R15, and C12 connected in parallel between the resistor R14 and the resistor R15. The third low-pass filter circuit includes R13 connected in series with the output terminal of the first amplification module, R16 connected in series with the output terminal of the second amplification module, C14 connected in parallel with the resistor R13, C113 connected in parallel with the resistor R16, and C15 connected in parallel between the resistor R13 and the resistor R16.

6. The differential amplification and adjustable gain detection system for single-molecule thermal conductivity signals according to claim 1, characterized in that: The first instrument amplification circuit includes an instrument amplifier A1, which operates in an amplification state. The positive terminal of the instrument amplifier A1 is connected to the output signal of the first low-pass filter circuit to amplify the output signal of the first low-pass filter circuit. The instrument amplifier A1 is connected to a gain setting resistor RG1, and adjusting the resistance value of the gain setting resistor RG1 can change the gain of the instrument amplifier A1. The second instrument amplification circuit includes an instrument amplifier A2, which operates in an amplification state. The positive and negative terminals of the instrument amplifier A2 are respectively connected to the output signal of the second low-pass filter circuit to amplify the output signal of the second low-pass filter circuit. The instrument amplifier A2 is connected to a gain setting resistor RG2, and adjusting the resistance value of the gain setting resistor RG2 can change the gain of the instrument amplifier A2.

7. The differential amplification and adjustable gain detection system for single-molecule thermal conductivity signals according to claim 1, characterized in that: The differential amplifier module includes an instrument amplifier A3, which operates in differential amplification mode. The positive and negative terminals of the instrument amplifier A3 are respectively connected to the output signal of the third low-pass filter circuit, and the instrument amplifier A3 differentially amplifies the two output signals of the third low-pass filter circuit.

8. The differential amplification and adjustable gain detection system for single-molecule thermal conductivity signals according to claim 7, characterized in that: The instrument amplifier A3 is connected to a gain setting resistor RG3. Adjusting the resistance value of the gain setting resistor RG3 can change the gain of the instrument amplifier A3.

9. The differential amplification and adjustable gain detection system for single-molecule thermal conductivity signals according to claim 1, characterized in that: The output of the differential amplifier module is connected to a filter to detect the single-molecule thermal conductivity AC signals of different frequencies.

10. A differential amplification and adjustable gain detection system for single-molecule thermal conductivity signals according to claim 9, characterized in that: The filter includes an amplifier UF. The positive terminal of the amplifier UF is connected to the output signal of the differential amplifier module. The amplifier UF operates in filter mode. The positive terminal of the amplifier UF is connected in series with resistors R1 and R2. Adjusting the resistance values ​​of resistors R1 and / or R2 can change the filtering bandwidth of the amplifier UF, thereby realizing the detection of the single-molecule thermal conductivity AC signal at different frequencies.

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