CN114362691B

CN114362691B - AC small signal driving information pick-up circuit

Info

Publication number: CN114362691B
Application number: CN202210262375.XA
Authority: CN
Inventors: 补世荣; 罗宇; 陈柳; 谢沛臻
Original assignee: Yijiazi Chengdu Communication Co ltd
Current assignee: Yijiazi Chengdu Communication Co ltd
Priority date: 2022-03-17
Filing date: 2022-03-17
Publication date: 2022-05-24
Anticipated expiration: 2042-03-17
Also published as: CN114362691A

Abstract

One end of a drain electrode and a source electrode of the transistor is grounded, the other end of the drain electrode and the source electrode of the transistor is connected with an input end of a feedback network, an input end of a high-pass branch circuit and an output end of a low-pass branch circuit, and an input end of the low-pass branch circuit is connected with the alternating small signal; the output signal of the output end of the feedback network is connected with a transistor grid, the instantaneous current and the thermal noise current existing in the circuit contain rich harmonic components after the circuit is electrified, the feedback frequency selection network performs frequency selection on the instantaneous current and couples the instantaneous current to the transistor grid for amplification, the amplified frequency components are subjected to frequency selection through the feedback frequency selection network and are coupled to the transistor grid for re-amplification, the amplified frequency components tend to be in a stable state after being limited, and the stable signal passes through a high-pass branch and an output frequency selection network and then is output to an information pickup circuit; the resonance angular frequency of the feedback frequency-selecting network is made to follow the change of the external physical quantity, so that the signal output by the information pickup circuit contains the change information of the external physical quantity.

Description

AC small signal driving information pick-up circuit

Technical Field

The invention belongs to the technical field of electronic power and sensor, and particularly relates to an information pickup circuit which takes a capacitor as a sensitive element and is directly driven by an alternating current small signal.

Background

The world has entered the information age today, and in the process of utilizing information, the problem to be solved first is how to obtain accurate and reliable information, and sensors are the main way and means to obtain information in the fields of nature and production. Sensors have long penetrated an extremely wide range of fields such as industrial production, space development, marine exploration, environmental protection, resource investigation, medical diagnosis, bioengineering, and even cultural relic protection. It is not an exaggeration to say that almost every modernization project is not separated from the various sensors.

The sensor generally comprises a sensing element, a conversion circuit and an auxiliary power supply. The sensitive element directly senses the measured information and outputs a physical quantity signal which has a determined relation with the measured information; the conversion element converts the physical quantity signal output by the sensitive element into an electric signal; the conversion circuit is responsible for amplifying and modulating the electric signal output by the conversion element, and the conversion element and the conversion circuit generally need an auxiliary direct-current power supply. However, due to the limitation of the electric quantity of the battery, the sensor battery needs to be replaced at certain intervals; when the battery power is insufficient, the measurement accuracy of the sensor is also deteriorated; meanwhile, the battery has the risk of high-temperature explosion, so that the sensor powered by the direct-current battery is limited in some special occasions, such as high-voltage side temperature and the like.

Disclosure of Invention

Aiming at the problem of limitation of the sensor caused by power supply based on the direct current power supply, the invention provides the information pickup circuit to replace the traditional sensor, the alternating current is directly used for replacing the direct current power supply to supply power for the information pickup circuit, and the feedback frequency selection network is used for acquiring the change of the external physical quantity, so that the signal output by the information pickup circuit can load the change information of the external physical quantity.

The invention utilizes alternating current small signals (such as power frequency signals) to carry out time-varying drive on the equivalent reactance of the transistor below the threshold voltage of the transistor, utilizes the time-varying drive to realize parametric amplification, ensures that a single transistor realizes amplification work in a half power frequency period, utilizes two transistors to realize full power frequency period amplification, and has the characteristics of direct alternating current drive and low energy consumption.

The invention adopts a technical scheme that a single transistor is adopted to realize the direct drive of half-cycle alternating current small signals for information pickup, and the technical scheme comprises the following steps:

the alternating current small signal drives an information pickup circuit, the information pickup circuit comprises a transistor, a first inductor, an output frequency selection network, a feedback network and a feed network, the feed network comprises a high-pass branch and a low-pass branch, one end of a drain electrode and one end of a source electrode of the transistor are grounded, and the other end of the drain electrode are connected with an input end of the feedback network, an input end of the high-pass branch and an output end of the low-pass branch; the output end of the feedback network is connected with the grid electrode of the transistor; the input end of the low-pass branch is connected with the alternating current small signal; the input end of the output network is connected with the output end of the high-pass branch, and the output end of the output network is used as the output end of the information pickup circuit;

the parasitic grid source capacitor, the grid drain capacitor or the drain source capacitor of the transistor below the threshold voltage is connected with the first inductor in series or in parallel to form a resonant frequency selection network, and the capacitance value C of the parasitic grid source capacitor, the grid drain capacitor or the drain source capacitor of the transistor and the inductance value L of the first inductor are set to meet the requirement

，

Setting the operating frequency of the output frequency-selective network equal to the initial resonant angular frequency of the feedback network

(ii) a When the resonance angular frequency of the feedback network is related to the change of the external physical quantity, the signal output by the output end of the information pickup circuit contains the change information of the external physical quantity;

the information pick-up circuit works in a half period of the working period of the alternating current small signal, and the frequency of the alternating current small signal is less than one tenth of the initial resonant frequency of the feedback frequency selection network.

A parasitic gate-source capacitor of a transistor is connected in parallel with a first inductor to form a resonant frequency selection network, and the first inductor is connected between a gate and a source of the transistor; when the source electrode of the transistor is grounded and the drain electrode of the transistor is connected with the input end of the feedback network and the feed network, the information pick-up circuit works in the positive half period of the working period of the alternating small signal; when the drain electrode of the transistor is grounded and the source electrode of the transistor is connected with the input end of the feedback network and the feed network, the information pick-up circuit works in the negative half period of the working period of the alternating small signal;

or, a parasitic gate-source capacitor of the transistor is connected in series with a first inductor to form a resonant frequency-selecting network, and the first inductor is connected between the output end of the feedback network and the gate of the transistor; when the source electrode of the transistor is grounded and the drain electrode of the transistor is connected with the input end of the feedback network and the feed network, the information pick-up circuit works in the positive half period of the working period of the alternating small signal; when the drain electrode of the transistor is grounded and the source electrode of the transistor is connected with the input end of the feedback network and the feed network, the information pick-up circuit works in the negative half period of the working cycle of the alternating small signal.

A parasitic gate-drain capacitor of a transistor is connected in parallel with a first inductor to form a resonant frequency-selecting network, and the first inductor is connected between a gate and a drain of the transistor; when the source electrode of the transistor is grounded and the drain electrode of the transistor is connected with the input end of the feedback network and the feed network through a first inductor, the information pickup circuit works in the positive half period of the working period of the alternating small signal; when the drain electrode of the transistor is grounded and the source electrode of the transistor is connected with the input end of the feedback network and the feed network, the information pick-up circuit works in the negative half period of the working period of the alternating small signal;

or a parasitic grid-drain capacitor of the transistor is connected with a first inductor in series to form a resonant frequency-selecting network, and the first inductor is connected with the drain electrode of the transistor; when the source electrode of the transistor is grounded and the drain electrode of the transistor is connected with the input end of the feedback network and the feed network through a first inductor, the information pickup circuit works in the positive half period of the working period of the alternating small signal; when the drain electrode of the transistor is grounded through the first inductor and the source electrode of the transistor is connected with the input end of the feedback network and the feed network, the information pick-up circuit works in the negative half period of the working period of the alternating current small signal.

A parasitic drain-source capacitor of a transistor is connected in parallel with a first inductor to form a resonant frequency selection network, and the first inductor is connected between a drain electrode and a source electrode of the transistor; when the source electrode of the transistor is grounded and the drain electrode of the transistor is connected with the input end of the feedback network and the feed network, the information pick-up circuit works in the positive half period of the working period of the alternating small signal; when the drain electrode of the transistor is grounded and the source electrode of the transistor is connected with the input end of the feedback network and the feed network, the information pick-up circuit works in the negative half period of the working period of the alternating small signal;

or when a parasitic drain-source capacitor of the transistor is connected in series with the first inductor to form a resonant frequency-selecting network, the first inductor is connected with the source electrode of the transistor; when the source electrode of the transistor is grounded through a first inductor and the drain electrode of the transistor is connected with the input end of the feedback network and the feed network, the information pickup circuit works in the positive half period of the working period of the alternating small signal; when the drain electrode of the transistor is grounded and the source electrode of the transistor is connected with the input end of the feedback network and the feed network through the first inductor, the information pick-up circuit works in the negative half period of the working period of the alternating current small signal.

Specifically, the low-pass branch comprises a second inductor and a first capacitor, one end of the second inductor is used as an input end of the low-pass branch and is grounded after passing through the first capacitor, and the other end of the second inductor is used as an output end of the low-pass branch; the high-pass branch comprises a third inductor and a second capacitor, one end of the second capacitor is used as the input end of the high-pass branch, and the other end of the second capacitor is used as the output end of the high-pass branch and is grounded after passing through the third inductor.

Specifically, the feedback network is formed by connecting a fourth inductor and a fifth inductor in series and then connecting the fourth inductor and the fifth inductor in parallel with a variable capacitor, and the series point of the fourth inductor and the fifth inductor is grounded; the capacitance value of the variable capacitor changes with the change of the external physical quantity.

Or the feedback network is formed by connecting a third capacitor and a fourth capacitor in series and then connecting the third capacitor and the fourth capacitor in parallel with a variable inductor, and the series point of the third capacitor and the fourth capacitor is grounded; the inductance value of the variable inductor changes with the change of the external physical quantity.

Or the feedback network consists of a variable capacitor and a transformer, wherein one end of a first winding of the transformer is connected with one end of the variable capacitor and is used as the input end of the feedback network, and the other end of the first winding of the transformer is connected with the other end of the variable capacitor and is grounded; one end of the second winding of the transformer is grounded, and the other end of the transformer is used as the output end of the feedback network.

The invention adopts two transistors to realize the full-period alternating current small signal direct drive for information pickup, and the technical scheme is as follows:

the alternating current small signal drives an information pickup circuit, the information pickup circuit works in the whole period of the working period of the alternating current small signal, the information pickup circuit comprises a power synthesizer and two information pickup circuit units, and the power synthesizer combines output signals of the two information pickup circuit units into one signal and then the signal is used as the output signal of the whole information pickup circuit;

the information pickup circuit unit comprises a transistor, a first inductor, an output frequency selection network, a feedback network and a feed network, wherein the feed network comprises a high-pass branch and a low-pass branch, and the input end of the low-pass branch is connected with the alternating current small signal; the input end of the high-pass branch is connected with the input end of an output frequency-selecting network, and the output end of the output frequency-selecting network is used as the output end of the information pickup circuit unit;

the first information pick-up circuit unit works in the positive half period of the working period of the alternating small signal, wherein the source electrode of the transistor is grounded; the drain electrode of the transistor is connected with the input end of the high-pass branch, the input end of the feedback frequency-selecting network and the output end of the low-pass branch; the grid electrode of the transistor is connected with a signal output by the output end of the feedback frequency selection network;

the second information pick-up circuit unit works in the negative half period of the working period of the alternating current small signal, wherein the drain electrode of the transistor is grounded; the source electrode of the transistor is connected with the input end of the high-pass branch circuit, the input end of the feedback network and the output end of the low-pass branch circuit; the grid electrode of the transistor is connected with the output end of the feedback network;

in each information pickup circuit unit, a parasitic gate-source capacitor, a gate-drain capacitor or a drain-source capacitor of a transistor below a threshold voltage is connected with a first inductor in series or in parallel to form a resonant frequency selection network, and the capacitance value C of the parasitic gate-source capacitor, the gate-drain capacitor or the drain-source capacitor of the transistor and the inductance value L of the first inductor are set to satisfy

，

the initial resonant angular frequencies of the feedback frequency-selecting networks in the two information pickup circuit units are the same, and the frequency of the alternating current small signal is less than one tenth of the initial resonant frequency of the feedback frequency-selecting networks;

the resonance angular frequency of the feedback networks in the two information pickup circuit units is related to the change of the same external physical quantity, and the signal output by the output end of the whole information pickup circuit contains the change information of the external physical quantity.

A parasitic gate-source capacitor of a transistor is connected in parallel with a first inductor to form a resonant frequency selection network, and the first inductor is connected between a gate and a source of the transistor; when the source electrode of the transistor is grounded and the drain electrode of the transistor is connected with the input end of the feedback network and the feed network, the information pick-up circuit unit works in the positive half period of the working period of the alternating small signal; when the drain electrode of the transistor is grounded and the source electrode of the transistor is connected with the input end of the feedback network and the feed network, the information pickup circuit unit works in the negative half period of the working cycle of the alternating small signal;

or, a parasitic gate-source capacitor of the transistor is connected in series with a first inductor to form a resonant frequency-selecting network, and the first inductor is connected between the output end of the feedback network and the gate of the transistor; when the source electrode of the transistor is grounded and the drain electrode of the transistor is connected with the input end of the feedback network and the feed network, the information pick-up circuit unit works in the positive half period of the working period of the alternating small signal; when the drain electrode of the transistor is grounded and the source electrode of the transistor is connected with the input end of the feedback network and the feed network, the information pick-up circuit unit works in the negative half period of the working period of the alternating small signal.

A parasitic grid-drain capacitor of a transistor is connected in parallel with a first inductor to form a resonant frequency-selecting network, and the first inductor is connected between a grid electrode and a drain electrode of the transistor; when the source electrode of the transistor is grounded and the drain electrode of the transistor is connected with the input end of the feedback network and the feed network through a first inductor, the information pickup circuit unit works in the positive half period of the working period of the alternating small signal; when the drain electrode of the transistor is grounded and the source electrode of the transistor is connected with the input end of the feedback network and the feed network, the information pick-up circuit unit works in the negative half period of the working period of the alternating small signal;

or a parasitic grid-drain capacitor of the transistor is connected with a first inductor in series to form a resonant frequency-selecting network, and the first inductor is connected with the drain electrode of the transistor; when the source electrode of the transistor is grounded and the drain electrode of the transistor is connected with the input end of the feedback network and the feed network through a first inductor, the information pickup circuit unit works in the positive half period of the working period of the alternating small signal; when the drain electrode of the transistor is grounded through the first inductor and the source electrode of the transistor is connected with the input end of the feedback network and the feed network, the information pickup circuit unit works in the negative half period of the working period of the alternating current small signal.

A parasitic drain-source capacitor of a transistor is connected in parallel with a first inductor to form a resonant frequency selection network, and the first inductor is connected between a drain electrode and a source electrode of the transistor; when the source electrode of the transistor is grounded and the drain electrode of the transistor is connected with the input end of the feedback network and the feed network, the information pick-up circuit unit works in the positive half period of the working period of the alternating small signal; when the drain electrode of the transistor is grounded and the source electrode of the transistor is connected with the input end of the feedback network and the feed network, the information pick-up circuit unit works in the negative half period of the working period of the alternating small signal;

or when a parasitic drain-source capacitor of the transistor is connected in series with the first inductor to form a resonant frequency-selecting network, the first inductor is connected with the source electrode of the transistor; when the source electrode of the transistor is grounded through a first inductor and the drain electrode of the transistor is connected with the input end of the feedback network and the feed network, the information pickup circuit unit works in the positive half period of the working period of the alternating small signal; when the drain electrode of the transistor is grounded and the source electrode of the transistor is connected with the input end of the feedback network and the feed network through the first inductor, the information pickup circuit unit works in the negative half period of the working period of the alternating current small signal.

Specifically, in the information pickup circuit unit, the low-pass branch includes a second inductor and a first capacitor, one end of the second inductor is used as an input end of the low-pass branch and is grounded after passing through the first capacitor, and the other end of the second inductor is used as an output end of the low-pass branch; the high-pass branch comprises a third inductor and a second capacitor, one end of the second capacitor is used as the input end of the high-pass branch, and the other end of the second capacitor is used as the output end of the high-pass branch and is grounded after passing through the third inductor.

Specifically, in the information pickup circuit unit, the feedback network is formed by connecting a fourth inductor and a fifth inductor in series and then connecting the fourth inductor and the fifth inductor in parallel, and a series point of the fourth inductor and the fifth inductor is grounded; the capacitance value of the variable capacitor changes with the change of the external physical quantity.

Or, in the information pickup circuit unit, the feedback network is formed by connecting a third capacitor and a fourth capacitor in series and then connecting the third capacitor and the fourth capacitor in parallel with a variable inductor, and the series point of the third capacitor and the fourth capacitor is grounded; the inductance value of the variable inductor changes with the change of the external physical quantity.

Or, in the information pickup circuit unit, the feedback network is composed of a variable capacitor and a transformer, wherein one end of a first winding of the transformer is connected with one end of the variable capacitor and serves as an input end of the feedback network, and the other end of the first winding of the transformer is connected with the other end of the variable capacitor and is grounded; one end of the second winding of the transformer is grounded, and the other end of the transformer is used as the output end of the feedback network.

The invention has the beneficial effects that:

firstly, the invention can directly utilize the AC small signal to drive and realize information pickup, solves the limitation problem caused by the need of DC power supply for driving the traditional sensor, and can be widely applied to various occasions.

Secondly, the invention utilizes the feedback network to follow the change of the external physical quantity, thereby acquiring the change information of the external physical quantity and realizing the information pickup function.

Moreover, the invention provides three information pickup structures working in the positive half cycle, the negative half cycle and the full cycle of the alternating current small signal, and provides a scheme for realizing a resonant frequency selection network by connecting a parasitic gate-source capacitor, a gate-drain capacitor or a drain-source capacitor of a transistor in series or in parallel with a first inductor and three structures of a feedback network, so that the invention has flexible application and wide application range.

Finally, the invention has no strict requirement on the magnitude of the driving voltage, and the information pickup circuit provided by the invention can work even if the power frequency driving voltage is smaller or the amplitude of the power frequency voltage serving as the bias is higher than the threshold voltage of the transistor.

Drawings

The following description of various embodiments of the invention may be better understood with reference to the following drawings, which schematically illustrate major features of some embodiments of the invention. These figures and examples provide some embodiments of the invention in a non-limiting, non-exhaustive manner. For purposes of clarity, the same reference numbers will be used in different drawings to identify the same or similar elements or structures having the same function.

Fig. 1 is a schematic structural diagram of an ac small-signal driving information pickup circuit according to the present invention, in which a transistor gate-source capacitor and a first inductor are connected in parallel to form a resonant frequency-selective network, and a positive power frequency period power frequency direct driving information pickup circuit is implemented based on a first feedback frequency-selective network structure.

Fig. 2 is a schematic structural diagram of an ac small-signal driving information pickup circuit according to the present invention, in which a transistor gate-source capacitor and a first inductor are connected in series to form a resonant frequency-selective network, and a positive power frequency period power frequency direct driving information pickup circuit is implemented based on a first feedback frequency-selective network structure.

Fig. 3 is a schematic structural diagram of an alternating-current small-signal driving information pickup circuit, which is provided by the invention, and adopts a resonant frequency-selecting network formed by connecting a transistor gate-source capacitor and a first inductor in parallel, and realizes that the information pickup circuit is directly driven by power frequency in a negative power frequency period based on a first feedback frequency-selecting network structure.

Fig. 4 is a schematic structural diagram of an alternating current small signal driving information pickup circuit provided by the present invention, in which a transistor gate-source capacitor and a first inductor are connected in series to form a resonant frequency selection network, and a negative power frequency cycle power frequency direct driving information pickup circuit is realized based on a first feedback frequency selection network structure.

Fig. 5 is a schematic structural diagram of an ac small-signal driving information pickup circuit according to the present invention, in which a transistor gate-source capacitor and a first inductor are connected in parallel to form a resonant frequency-selective network, and a full power frequency cycle power frequency direct driving information pickup circuit is implemented based on a first feedback frequency-selective network structure.

Fig. 6 is a schematic structural diagram of an ac small-signal driving information pickup circuit according to the present invention, in which a transistor gate-source capacitor and a first inductor are connected in series to form a resonant frequency-selective network, and a full power frequency cycle power frequency direct driving information pickup circuit is implemented based on a first feedback frequency-selective network structure.

Fig. 7 is a schematic structural diagram of an ac small-signal driving information pickup circuit according to the present invention, in which a transistor gate-drain capacitor and a first inductor are connected in parallel to form a resonant frequency-selective network, and a positive power frequency period power frequency direct-driving information pickup circuit is implemented based on a first feedback frequency-selective network structure.

Fig. 8 is a schematic structural diagram of an ac small-signal driving information pickup circuit according to the present invention, in which a transistor gate-drain capacitor and a first inductor are connected in series to form a resonant frequency-selective network, and a positive power frequency period power frequency direct-driving information pickup circuit is implemented based on a first feedback frequency-selective network structure.

Fig. 9 is a schematic structural diagram of an ac small-signal driving information pickup circuit according to the present invention, in which a transistor gate-drain capacitor and a first inductor are connected in parallel to form a resonant frequency-selective network, and a negative power frequency cycle power frequency direct-driving information pickup circuit is implemented based on a first feedback frequency-selective network structure.

Fig. 10 is a schematic structural diagram of an ac small-signal driving information pickup circuit according to the present invention, in which a transistor gate-drain capacitor and a first inductor are connected in series to form a resonant frequency-selective network, and a negative power frequency cycle power frequency direct-driving information pickup circuit is implemented based on a first feedback frequency-selective network structure.

Fig. 11 is a schematic structural diagram of an ac small-signal driving information pickup circuit according to the present invention, in which a transistor gate-drain capacitor and a first inductor are connected in parallel to form a resonant frequency-selective network, and a full power frequency cycle power frequency direct driving information pickup circuit is implemented based on a first feedback frequency-selective network structure.

Fig. 12 is a schematic structural diagram of an ac small-signal driving information pickup circuit according to the present invention, in which a transistor gate-drain capacitor and a first inductor are connected in series to form a resonant frequency-selective network, and a full power frequency cycle power frequency direct driving information pickup circuit is implemented based on a first feedback frequency-selective network structure.

Fig. 13 is a schematic structural diagram of an ac small-signal driving information pickup circuit according to the present invention, in which a transistor drain-source capacitor and a first inductor are connected in parallel to form a resonant frequency-selective network, and a positive power frequency period power frequency direct driving information pickup circuit is implemented based on a first feedback frequency-selective network structure.

Fig. 14 is a schematic structural diagram of an ac small-signal driving information pickup circuit according to the present invention, in which a transistor drain-source capacitor and a first inductor are connected in series to form a resonant frequency-selective network, and a positive power frequency period power frequency direct driving information pickup circuit is implemented based on a first feedback frequency-selective network structure.

Fig. 15 is a schematic structural diagram of an ac small-signal driving information pickup circuit according to the present invention, in which a transistor drain-source capacitor and a first inductor are connected in parallel to form a resonant frequency-selective network, and a negative power frequency cycle power frequency direct-driving information pickup circuit is implemented based on a first feedback frequency-selective network structure.

Fig. 16 is a schematic structural diagram of an ac small-signal driving information pickup circuit according to the present invention, in which a transistor drain-source capacitor and a first inductor are connected in series to form a resonant frequency-selective network, and a negative power frequency cycle power frequency direct driving information pickup circuit is implemented based on a first feedback frequency-selective network structure.

Fig. 17 is a schematic structural diagram of an ac small-signal driving information pickup circuit according to the present invention, in which a transistor drain-source capacitor and a first inductor are connected in parallel to form a resonant frequency-selective network, and a full power frequency cycle power frequency direct driving information pickup circuit is implemented based on a first feedback frequency-selective network structure.

Fig. 18 is a schematic structural diagram of an ac small-signal driving information pickup circuit according to the present invention, in which a transistor drain-source capacitor and a first inductor are connected in series to form a resonant frequency-selective network, and a full power frequency cycle power frequency direct driving information pickup circuit is implemented based on a first feedback frequency-selective network structure.

Fig. 19 is one of the graphs of time varying capacitance/voltage of the transistor oscillator in the ac small signal driving information pick-up circuit according to the present invention.

Fig. 20 is a second time-varying capacitance/voltage curve diagram of the transistor oscillator in the ac small-signal driving information pickup circuit according to the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in detail with reference to the accompanying drawings. It is to be understood that the disclosed embodiments are merely exemplary of the invention, and are not intended to be exhaustive or exhaustive. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The invention provides an information pickup circuit without power supply of a direct current power supply, which replaces a traditional sensor powered by the direct current power supply to acquire the change of external physical quantity. In detail, based on the characteristic that the gate-source capacitance of the transistor below the threshold voltage is strong nonlinear, the parasitic gate-source capacitance, the gate-drain capacitance or the drain-source capacitance of the transistor below the threshold voltage and the first inductor are connected in series or in parallel to form a resonant frequency selection network, so that the equivalent reactance of the transistor is subjected to time-varying driving by using an alternating current small signal (such as a power frequency signal) below the threshold voltage of the transistor, and the time-varying driving can realize parametric amplification and complete the amplification effect of the transistor; thus, the information pick-up circuit provided by the invention can be directly driven by using the alternating current small signal without the power supply of a direct current power supply.

In order to obtain the change of the external physical quantity, the resonance angular frequency of the feedback network is made to follow the change of the external physical quantity, so that the signal output by the information pickup circuit loads the change information of the external physical quantity. The resonance angular frequency of the feedback network is set to be an initial value, the resonance angular frequency of the feedback frequency-selecting network does not change much along with external physical quantity, so that the difference between the changed resonance angular frequency of the feedback network and the initial value is not large, and therefore, the alternating current small signal can be set to be a signal with the frequency lower than one tenth of the initial resonance frequency of the feedback network, for example, a 50Hz power frequency signal or other suitable signals can be used as driving input. The transistor is a transistor capable of operating in the radio frequency microwave frequency band, such as a field effect transistor or other kinds of transistors satisfying the conditions.

The amplification can be realized in a half cycle (including a positive half cycle and a negative half cycle) of the alternating current small signal by using a single transistor, the amplification can be realized in a full cycle by using two transistors, three conditions of the positive half cycle, the negative half cycle and the full cycle are respectively explained below, and the alternating current small signal is explained by taking a 50Hz power frequency signal as an example in the embodiment.

Fig. 1, fig. 3 and fig. 5 are schematic structural diagrams illustrating that a transistor gate source capacitor and a first inductor are connected in parallel to form a resonant frequency selection network to respectively realize positive half-cycle operation, negative half-cycle operation and full-cycle operation, and fig. 2, fig. 4 and fig. 6 are schematic structural diagrams illustrating that a transistor gate source capacitor and a first inductor are connected in series to form a resonant frequency selection network to respectively realize positive half-cycle operation, negative half-cycle operation and full-cycle operation. Fig. 1 to 7 all adopt a first feedback frequency selection network, the first feedback network is formed by connecting a fourth inductor and a fifth inductor in series and then connecting the fourth inductor and the fifth inductor in parallel with a variable capacitor, wherein a series point of the fourth inductor and the fifth inductor is grounded. The feedback network acquires the change of the external physical quantity by using the variable capacitor, and when the external physical quantity (such as temperature, pressure and the like) changes, the capacitance value of the variable capacitor also changes, so that the output of the frequency selection network is loaded with the signal to be demodulated of the information. When the variable capacitor is a varactor, the information pickup circuit provided by the invention can pick up voltage information.

Fig. 7, 9 and 11 are schematic structural diagrams illustrating a resonant frequency-selecting network formed by connecting a transistor gate-drain capacitor in parallel with a first inductor to respectively realize positive half-cycle operation, negative half-cycle operation and full-cycle operation, and fig. 8, 10 and 12 are schematic structural diagrams illustrating a resonant frequency-selecting network formed by connecting a transistor gate-drain capacitor in series with a first inductor to respectively realize positive half-cycle operation, negative half-cycle operation and full-cycle operation. Fig. 8 to 12 all adopt a first feedback frequency selection network, where the first feedback network is formed by connecting a fourth inductor and a fifth inductor in series and then connecting them in parallel with a variable capacitor, and a series point of the fourth inductor and the fifth inductor is grounded. The feedback network acquires the change of the external physical quantity by using the variable capacitor, and when the external physical quantity (such as temperature, pressure and the like) changes, the capacitance value of the variable capacitor also changes, so that the output of the frequency selection network is loaded with the signal to be demodulated of the information. When the variable capacitor is a varactor, the information pickup circuit provided by the invention can pick up voltage information.

Fig. 13, 15 and 17 are schematic structural diagrams illustrating that the drain-source capacitance of the transistor is connected in parallel with the first inductor to form the resonant frequency selection network to respectively realize positive half-cycle operation, negative half-cycle operation and full-cycle operation, and fig. 14, 16 and 18 are schematic structural diagrams illustrating that the drain-source capacitance of the transistor is connected in series with the first inductor to form the resonant frequency selection network to respectively realize positive half-cycle operation, negative half-cycle operation and full-cycle operation. Fig. 13 to 18 all adopt a first feedback frequency selection network, where the first feedback network is formed by connecting a fourth inductor and a fifth inductor in series and then connecting them in parallel with a variable capacitor, and a series point of the fourth inductor and the fifth inductor is grounded. The feedback network acquires the change of the external physical quantity by using the variable capacitor, and when the external physical quantity (such as temperature, pressure and the like) changes, the capacitance value of the variable capacitor also changes, so that the output of the frequency selection network is loaded with the signal to be demodulated of the information. When the variable capacitor is a varactor, the information pickup circuit provided by the invention can pick up voltage information.

In the ac small-signal driving information pickup circuit shown in fig. 1 to 18, the feedback network may be replaced by a second feedback network. The second feedback network is formed by connecting a third capacitor and a fourth capacitor in series and then connecting the third capacitor and the fourth capacitor in parallel with a variable inductor, wherein the series point of the third capacitor and the fourth capacitor is grounded. In the second feedback frequency-selecting network, the variable inductor is used to obtain the change of the external physical quantity, when the external physical quantity (such as temperature, pressure, etc.) changes, the inductance value of the variable inductor also changes, so that the output of the output frequency-selecting network loads the signal to be demodulated of the information. When the variable inductance is an inductance that varies with a change in current, the information pickup circuit proposed by the present invention can pick up current information.

In the ac small-signal driving information pickup circuit shown in fig. 1 to 18, the feedback network may be replaced by a third feedback network. The third feedback network consists of a variable capacitor and a transformer, wherein one end of a first winding of the transformer is connected with one end of the variable capacitor and is used as the input end of the feedback network, and the other end of the first winding of the transformer is connected with the other end of the variable capacitor and is grounded; one end of the second winding of the transformer is grounded, and the other end of the transformer is used as the output end of the feedback network. The third feedback network is similar to the first feedback network, and the change of the external physical quantity is obtained by using the variable capacitor, and when the external physical quantity (such as temperature, pressure and the like) changes, the capacitance value of the variable capacitor also changes, so that the output of the frequency selection network is loaded with the signal to be demodulated of the information.

The feedback network is used for carrying out frequency selection on the current containing harmonic components in the information pickup circuit after being electrified and coupling the current to the grid electrode of the transistor for amplification, and the amplified frequency components are subjected to frequency selection through the feedback network and are coupled to the grid electrode of the transistor for re-amplification. And the resonance angular frequency based on the feedback frequency selection network changes along with the change of the external physical quantity, so that the information pickup circuit can acquire the change information of the external physical quantity. The working process of the present invention will be described below by taking fig. 1, 3 and 5 as examples only.

Fig. 1 shows a case where the information pickup circuit operates in the positive half cycle of the power frequency cycle. In this embodiment, the gate-source capacitor of the transistor is connected in parallel with the first inductor, so that the output end of the feedback network is directly connected to the gate of the transistor, and the input end of the feedback network is connected to the drain of the transistor, the input end of the high-pass branch and the output end of the low-pass branch in the feed network; the source electrode of the transistor is grounded, and the first inductor is connected between the grid electrode and the source electrode of the transistor, so that the first inductor and the grid-source capacitor of the transistor are connected in parallel to form a resonant frequency-selective network; the input end of the output frequency selection network is connected with the output end of the high-pass branch in the feed network, and the output end of the output frequency selection network is used as the output end of the information pickup circuit.

The feed network comprises a high-pass branch and a low-pass branch, wherein the input end of the low-pass branch is connected with an alternating current small signal, in the embodiment, a 50Hz power frequency signal is used as a driving input, the low-pass branch allows the alternating current small signal to pass through and output to the transistor, and the high-pass branch allows the signal amplified by the transistor to pass through the frequency selection network for output. As shown in fig. 1, an implementation structure of a feed network is provided, and of course, other feed networks formed by structures that allow high-frequency signals to pass and low-frequency signals to pass can also be applied to the present invention, in this embodiment, the low-pass branch includes a second inductor and a first capacitor, one end of the second inductor is used as an input end of the low-pass branch to be connected to a 50Hz power frequency signal and grounded after passing through the first capacitor, and the other end thereof is used as an output end of the low-pass branch to be connected to a drain of a transistor; the high-pass branch comprises a third inductor and a second capacitor, one end of the second capacitor is used as an input end of the high-pass branch to be connected with the drain electrode of the transistor, and the other end of the second capacitor is used as an output end of the high-pass branch to be connected with the input end of the second frequency-selecting network and is grounded through the third inductor.

The working process of the structure shown in fig. 1 is as follows: at the moment of power-on, the instantaneous current and the thermal noise current existing in the circuit contain rich harmonic components, the harmonic components are subjected to frequency selection through the feedback network and are coupled to the grid electrode of the transistor for amplification, the amplified frequency components are subjected to frequency selection through the feedback network and are coupled to the grid electrode of the transistor for re-amplification, and due to the nonlinearity of the transistor, the process cannot be continued all the time and finally tends to a stable state. The stabilized frequency signals can only flow out from the high-pass branch of the feed network through the feed network, and the signals flowing out from the high-pass branch are subjected to impedance matching by the output frequency-selecting network and then are sent out. That is, due to the effect of the feedback network, the output end of the feedback network outputs a signal with a certain frequency, and in this embodiment, the variable capacitor is adopted to follow the change of external physical information, so that the frequency signal output by the feedback frequency selection network changes correspondingly, thereby completing the information pickup. The circuit with the structure shown in fig. 1 operates only in the positive half cycle of the power frequency cycle, which is determined by the capacitance/voltage characteristics of the transistor, and is specifically described as follows:

under the drive of the sinusoidal bias voltage shown in FIG. 19A and FIG. 20A, when the bias voltage V is applied_DS≤V_tIn which V is_tFor the threshold voltage of the transistor, the capacitance/voltage characteristic between the source and the gate of the transistor at this time is shown as B in FIG. 19, and the gate-source capacitance C of the transistor in the positive half cycle of the bias voltage_GSWith a strongly non-linear variation.

The information pick-up circuit provided by the invention utilizes the transistor to realize parametric amplification, and is different from the prior transistor to realize parametric amplification in that the pumping frequency of the prior parametric amplifier is about twice of the frequency of an input signal of the amplifier,the input signal amplified in the invention is approximately equal to the output signal of the information pickup circuit, and the pumping frequency of the invention can be far lower than the output signal of the information pickup circuit, namely lower than one tenth of the output signal frequency of the information pickup circuit, namely lower than one tenth of the initial resonance frequency of the feedback network, such as 50Hz power frequency. In fact, for a nonlinear device, when power is input at some specific frequency, the input power will be transferred to other newly generated frequency points to be output after nonlinear conversion, that is, the total input power and the total output power at all frequency points are conserved, without considering loss. In parametric amplifiers, this relationship is determined by the Menley equation (equations 1a and 1 b), where

For the amplifier input signal angular frequency (i.e. the resonant angular frequency of the feedback frequency-selective network),

for the angular frequency of the pump signal i.e. the ac small signal,

is at an angular frequency of

) M and n are the harmonic orders of the amplifier output signal and the pump signal, respectively.

（1a）

（1b）

Therefore, the invention utilizes the strong nonlinear capacitance of the transistor below the threshold voltage, namely the grid source capacitance C_GSAnd the first inductor L in FIG. 1 form a resonant frequency-selective network and make the crystalCapacitance C of transistor gate and source capacitance_GS0And the inductance value L of the first inductor satisfies the condition:

simultaneously setting an output frequency selection network and a feedback network to work

Nearby. This will cause the circuit to be at the signal frequency

And gain is arranged nearby, so that parametric amplification is realized under the power frequency bias condition by utilizing the nonlinear capacitance of the transistor. It should be noted that the circuit shown in fig. 1 can be operated in an enlarged manner during the nearly positive half cycle of the power frequency cycle shown in fig. 19B, and therefore the circuit shown in fig. 1 can be operated during the positive half cycle of the power frequency cycle.

Fig. 3 shows the case where the information pickup circuit operates in the negative half cycle of the power frequency cycle. The output end of the feedback network is connected with the grid of the transistor, and the input end of the feedback network is connected with the source electrode of the transistor, the input end of the high-pass branch and the output end of the low-pass branch in the feed network; the drain electrode of the transistor is grounded, and the first inductor is connected between the grid electrode and the source electrode of the transistor, so that the first inductor and the grid-source capacitor of the transistor are connected in parallel to form a resonant frequency-selective network; the input end of the output frequency selection network is connected with the output end of the high-pass branch in the feed network, and the output end of the output frequency selection network outputs a signal to be demodulated loaded with external physical quantity change information.

The working process of the structure shown in fig. 3 is as follows: at the moment of power-on, the transient current and the thermal noise current existing in the circuit contain rich harmonic components, the harmonic components are subjected to frequency selection through the feedback network and coupled to the grid electrode of the transistor for amplification, the amplified frequency components are subjected to frequency selection through the feedback network and coupled to the grid electrode of the transistor for re-amplification, and due to the nonlinearity of the transistor, the process cannot be continued all the time and finally tends to a stable state. The stabilized frequency signals can only flow out from the high-pass branch of the feed network through the feed network, and the signals flowing out from the high-pass branch are subjected to impedance matching by the output frequency-selecting network and then are sent out. That is, due to the effect of the feedback frequency selection network, the output end of the feedback frequency selection network can output a signal with a certain frequency, in this embodiment, the variable capacitor is adopted to follow the change of the external physical information, and when the variable capacitor changes along with the change of the external physical information, the frequency signal output by the feedback network can change correspondingly, thereby completing the information pickup.

The circuit of the configuration shown in fig. 3 operates only in the negative half of the power frequency cycle, as determined by the transistor capacitance/voltage characteristics. Under the drive of sinusoidal bias voltage as shown in FIG. 19A, when the bias voltage V is applied_DS≤V_tAt this time, the transistor capacitance/voltage characteristics are as shown in fig. 19C. When the bias voltage is in the negative half cycle of the power frequency cycle, the grid source capacitance C of the transistor_GSExhibits strong nonlinearity, and utilizes the strong nonlinear capacitance C of the transistor below the threshold voltage_GSAnd the first inductor L in FIG. 3 form a resonant frequency-selecting network, and the capacitance value C of the gate-source capacitance of the transistor is enabled_GS0And the inductance value L of the first inductor satisfies the condition:

simultaneously setting an output frequency selection network and a feedback frequency selection network to work

Nearby. This will cause the circuit to be at the signal frequency

And gain is arranged nearby, so that parametric amplification is realized under the power frequency bias condition by utilizing the nonlinear capacitance of the transistor. It should be noted that the circuit of fig. 3 can be operated in amplification during the near negative half of the power frequency cycle shown in fig. 19C, and thus the circuit of fig. 3 can be operated during the negative half of the power frequency cycle.

The structure of working in the positive half cycle of the power frequency cycle shown in fig. 1 and the structure of working in the negative half cycle of the power frequency cycle shown in fig. 3 are combined to obtain the information pickup circuit working in the full power frequency cycle shown in fig. 5, which comprises a power synthesizer and two information pickup units, wherein the variable capacitors of the feedback networks in the two information pickup units are the same, and the values of the two variable capacitors are the same with the change of external physical quantities (temperature, pressure and the like). The two information pickup units work in the positive half cycle and the negative half cycle of the power frequency cycle respectively, and output signals of the two information pickup units are used as output signals of the information pickup circuit after passing through the power combiner.

The first information pickup unit works in the positive half cycle of the power frequency cycle, the structure of the first information pickup unit is similar to that of the first information pickup unit in the structure of fig. 1, the output end of the feedback network 1 is connected with the grid electrode of the transistor, and the input end of the feedback network is connected with the drain electrode of the transistor, wherein one end of the first inductor L1 is connected with the grid electrode of the transistor FET1, the other end of the first inductor L1 is connected with the source electrode of the transistor FET1, the source electrode of the transistor FET1 is grounded, and the drain electrode of the transistor is connected with the input end of the high-pass branch and the output end of the low-pass branch in the feed network; the input end of the output frequency-selecting network is connected with the output end of the high-pass branch, and the output end of the output frequency-selecting network is connected with the first input end of the power synthesizer.

The second information pickup unit works in the negative half cycle of the power frequency cycle, the structure of the second information pickup unit is similar to that of the second information pickup unit in the structure of fig. 3, the output end of the feedback network 2 is connected with the grid electrode of the transistor, and the input end of the feedback network is connected with the source electrode of the transistor, wherein one end of the first inductor L2 is connected with the grid electrode of the transistor FET2, the other end of the first inductor L2 is connected with the source electrode of the transistor FET2, the drain electrode of the transistor FET2 is grounded, and the source electrode is connected with the input end of the high-pass branch and the output end of the low-pass branch in the feed network; the input end of the output frequency-selecting network is connected with the output end of the high-pass branch, and the output end of the output frequency-selecting network is connected with the second input end of the power synthesizer.

The initial resonant angular frequency of the feedback frequency-selecting networks in the two information pickup units is set to be the same, and can be driven by the same ac small signal, for example, in this embodiment, a 50Hz power frequency signal is input to the drain of the transistor FET1 and the source of the transistor FET2 through the low-pass branches in the feed networks of the two information pickup units, the low-pass branches include a second inductor and a first capacitor, and the low-pass branches of the two information pickup units can share the first capacitor.

The working process of the structure shown in fig. 5 is as follows: at the moment of power-on, the instantaneous current and the thermal noise current existing in the circuit contain rich harmonic wavesThe components are respectively subjected to frequency selection through the feedback network 1 and the feedback network 2 and coupled to the gates of the transistor FET1 and the transistor FET2 for amplification, the amplified frequency components are respectively subjected to frequency selection through the feedback network 1 and the feedback network 2 and coupled to the gates of the transistor FET1 and the transistor FET2 for re-amplification, and due to the nonlinearity of the transistors, the process cannot be continued all the time and finally tends to a stable state. Due to the action of the feedback network, the output ends of the two information pickup units can output signals with certain frequency, when the variable capacitance (variable inductance is adopted in some embodiments) changes along with the change of external physical information, the frequency signals output by the feedback frequency selection network in the two information pickup units can change correspondingly, the signals output by the drains or the sources of the transistors in the two information pickup units can only flow out from the high-pass branch of the feed network through the feed network, and the signals flowing out from the high-pass branch are subjected to impedance matching by the source frequency selection network or the drain frequency selection network and then are sent to the output power synthesizer to be synthesized into one path. The connection of the transistor FET1 shown in FIG. 5 is the same as that shown in FIG. 1, and the connection of the transistor FET2 shown in FIG. 5 is the same as that shown in FIG. 3, and is determined by the transistor capacitance/voltage characteristics when the bias voltage V is driven by the sinusoidal bias voltage shown in FIG. 19A_DS≤V_tIn the case of the power frequency period, the transistor FET1 shown in fig. 5 may perform amplification operation in a positive half cycle, and the transistor FET2 shown in fig. 5 may perform amplification operation in a negative half cycle, and output signals of the two transistors are synthesized by the power synthesizer and then output, so that the information pickup circuit having the structure shown in fig. 5 may perform operation in the entire power frequency period.

It should be noted that when V_DS≥V_tIn the circuit shown in fig. 5, the transistor for realizing parametric amplification has the same circuit characteristics as the transistor for realizing reference amplification in the conventional circuit, which greatly improves the dynamic range of the parametric amplification circuit.

The description of the working process of the alternating current small-signal information pickup circuit which respectively realizes the work of the power frequency positive period, the power frequency negative period and the whole period by utilizing the resonant frequency selection network formed by connecting the transistor gate-source capacitor and the first inductor in parallel is given above. An alternating current small signal information pick-up circuit which respectively realizes power frequency positive, negative and full-cycle work by using a resonant frequency selection network formed by connecting a transistor gate-drain capacitor with a first inductor in series (the circuit structure is shown in fig. 7, 8, 9, 10, 11 and 12, the gate-drain capacitance time-varying characteristic in positive half-cycle work is shown in fig. 20B, the gate-drain capacitance time-varying characteristic in negative half-cycle work is shown in fig. 20C), and the alternating current small signal information pick-up circuit which can form the resonant frequency selection network by using the transistor drain-source capacitor and the first inductor in series or parallel (the circuit structure is shown in fig. 13, 14, 15, 16, 17 and 18, the drain-source capacitance time-varying characteristic in positive half-cycle work is shown in fig. 19D and 20D, the drain-source capacitance time-varying characteristic in negative half-cycle work is shown in fig. 19E and 20E), the working processes are approximately the same, it is not described in detail.

In summary, the embodiments provide a resonant frequency selection network formed by connecting a transistor gate-source capacitor, a gate-drain capacitor, or a drain-source capacitor shown in fig. 1 to 18 in parallel with a first inductor, and various structures for implementing the structure of the information pickup circuit by using the first feedback frequency selection network to work in the positive half cycle, the negative half cycle, and the full power frequency cycle of the power frequency. The multiple structures can directly utilize AC small signal drive to realize the amplification of the transistor, so that information pickup can be directly driven by power frequency, and the device can be widely applied to various occasions. In addition, three feedback frequency selection network implementation structures are provided in the embodiment, so that the design of the invention is more flexible.

In addition, the invention has no strict requirement on the magnitude of the driving voltage, and by taking the structure shown in fig. 1 as an example, in the working process according to the embodiment shown in fig. 1, the invention finds that the circuit can also work in an amplifying way when the magnitude of the power frequency driving voltage is only 0.1V, and the voltage of 0.1V can be easily obtained on a power grid, thereby providing great convenience for the application of the information pickup circuit. Through the embodiment, the invention also finds that the transistor can realize amplification operation even if the power frequency voltage amplitude as the bias is higher than the threshold voltage of the transistor, and the transistor for realizing amplification in the circuit works in a normal amplification region with the bias voltage changed, so that the embodiment in fig. 1 can work in a wider bias voltage amplitude range.

It will be appreciated by those of ordinary skill in the art that the embodiments described herein are intended to assist the reader in understanding the principles of the invention and are to be construed as being without limitation to such specifically recited embodiments and examples. Various modifications and alterations to this invention will become apparent to those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the claims of the present invention.

Claims

1. The alternating current small signal driving information pickup circuit is characterized by comprising a transistor, a first inductor, an output frequency selection network, a feedback network and a feed network, wherein the feed network comprises a high-pass branch and a low-pass branch, one end of a drain electrode and a source electrode of the transistor is grounded, and the other end of the drain electrode and the source electrode of the transistor are connected with an input end of the feedback network, an input end of the high-pass branch and an output end of the low-pass branch; the output end of the feedback network is connected with the grid electrode of the transistor; the input end of the low-pass branch is connected with the alternating current small signal; the input end of the output frequency-selecting network is connected with the output end of the high-pass branch, and the output end of the output frequency-selecting network is used as the output end of the information pickup circuit;

，

(ii) a When resonance of the feedback networkWhen the angular frequency is related to the change of the external physical quantity, the signal output by the output end of the information pickup circuit contains the change information of the external physical quantity;

the information pick-up circuit works in a half period of the working period of the alternating small signal, and the frequency of the alternating small signal is less than one tenth of the initial resonant frequency of the feedback network.

2. The alternating small-signal driving information pickup circuit according to claim 1, characterized in that:

or a parasitic grid source capacitor of the transistor is connected in series with a first inductor to form a resonant frequency-selecting network, and the first inductor is connected between the output end of the feedback network and the grid electrode of the transistor; when the source electrode of the transistor is grounded and the drain electrode of the transistor is connected with the input end of the feedback network and the feed network, the information pick-up circuit works in the positive half period of the working period of the alternating small signal; when the drain electrode of the transistor is grounded and the source electrode of the transistor is connected with the input end of the feedback network and the feed network, the information pick-up circuit works in the negative half period of the working period of the alternating small signal.

3. The alternating small-signal driving information pickup circuit according to claim 1, characterized in that:

a parasitic gate-drain capacitor of a transistor is connected in parallel with a first inductor to form a resonant frequency-selecting network, and the first inductor is connected between a gate and a drain of the transistor; when the source electrode of the transistor is grounded and the drain electrode of the transistor is connected with the input end of the feedback network and the feed network, the information pick-up circuit works in the positive half period of the working period of the alternating small signal; when the drain electrode of the transistor is grounded and the source electrode of the transistor is connected with the input end of the feedback network and the feed network, the information pick-up circuit works in the negative half period of the working period of the alternating small signal;

4. The alternating small-signal driving information pickup circuit according to claim 1, characterized in that:

5. The AC small signal driving information pickup circuit according to any one of claims 1-4, wherein said low-pass branch comprises a second inductor and a first capacitor, one end of the second inductor is used as the input end of said low-pass branch and is grounded through the first capacitor, and the other end is used as the output end of said low-pass branch; the high-pass branch comprises a third inductor and a second capacitor, one end of the second capacitor is used as the input end of the high-pass branch, and the other end of the second capacitor is used as the output end of the high-pass branch and is grounded after passing through the third inductor.

6. The AC small signal driving information pick-up circuit according to any one of claims 1 to 4, wherein said feedback network is formed by connecting a fourth inductor and a fifth inductor in series and then connecting them in parallel with a variable capacitor, and the series connection point of the fourth inductor and the fifth inductor is grounded.

7. An AC small signal driving information pick-up circuit as claimed in any one of claims 1 to 4, wherein said feedback network is formed by connecting a third capacitor and a fourth capacitor in series and then connecting them in parallel with a variable inductor, and the series point of the third capacitor and the fourth capacitor is grounded.

8. An AC small signal driving information pick-up circuit as claimed in any one of claims 1 to 4, wherein said feedback network is composed of a variable capacitor and a transformer, wherein one end of the first winding of the transformer is connected to one end of the variable capacitor and serves as an input terminal of the feedback network, and the other end of the first winding of the transformer is connected to the other end of the variable capacitor and is grounded; one end of the second winding of the transformer is grounded, and the other end of the transformer is used as the output end of the feedback network.

9. The alternating current small signal driving information pickup circuit is characterized in that the information pickup circuit works in the whole period of the working period of the alternating current small signal, the information pickup circuit comprises a power combiner and two information pickup circuit units, and the power combiner combines output signals of the two information pickup circuit units into one signal and then the signal is used as an output signal of the whole information pickup circuit;

the first information pick-up circuit unit works in the positive half period of the working period of the alternating small signal, wherein the source electrode of the transistor is grounded; the drain electrode of the transistor is connected with the input end of the high-pass branch, the input end of the feedback network and the output end of the low-pass branch; the grid electrode of the transistor is connected with the output end of the feedback network;

，

the initial resonance angular frequencies of the feedback networks in the two information pickup circuit units are the same, and the frequency of the alternating current small signal is less than one tenth of the initial resonance frequency of the feedback networks;

10. The alternating-current small-signal driving information pickup circuit according to claim 9, wherein in the information pickup circuit unit:

a parasitic gate-source capacitor of a transistor is connected in parallel with a first inductor to form a resonant frequency selection network, and the first inductor is connected between a gate and a source of the transistor; when the source electrode of the transistor is grounded and the drain electrode of the transistor is connected with the input end of the feedback network and the feed network, the information pick-up circuit unit works in the positive half period of the working period of the alternating small signal; when the drain electrode of the transistor is grounded and the source electrode of the transistor is connected with the input end of the feedback network and the feed network, the information pick-up circuit unit works in the negative half period of the working period of the alternating small signal;

11. The alternating-current small-signal driving information pickup circuit according to claim 9, wherein in the information pickup circuit unit:

a parasitic gate-drain capacitor of a transistor is connected in parallel with a first inductor to form a resonant frequency-selecting network, and the first inductor is connected between a gate and a drain of the transistor; when the source electrode of the transistor is grounded and the drain electrode of the transistor is connected with the input end of the feedback network and the feed network, the information pick-up circuit unit works in the positive half period of the working period of the alternating small signal; when the drain electrode of the transistor is grounded and the source electrode of the transistor is connected with the input end of the feedback network and the feed network, the information pick-up circuit unit works in the negative half period of the working period of the alternating small signal;

12. The alternating-current small-signal driving information pickup circuit according to claim 9, wherein in the information pickup circuit unit:

13. An ac small-signal driving information pick-up circuit according to any one of claims 9-12, wherein in the information pick-up circuit unit, the low-pass branch comprises a second inductor and a first capacitor, one end of the second inductor is used as the input end of the low-pass branch and is grounded through the first capacitor, and the other end is used as the output end of the low-pass branch; the high-pass branch comprises a third inductor and a second capacitor, one end of the second capacitor is used as the input end of the high-pass branch, and the other end of the second capacitor is used as the output end of the high-pass branch and is grounded after passing through the third inductor.

14. The ac small-signal-drive information pickup circuit according to any one of claims 9 to 12, wherein in the information pickup circuit unit, the feedback network is formed by connecting a fourth inductor and a fifth inductor in series and then connecting them in parallel with a variable capacitor, and the series connection point of the fourth inductor and the fifth inductor is grounded.

15. An AC small signal driving information pick-up circuit as claimed in any one of claims 9-12, wherein in said information pick-up circuit unit, said feedback network is formed by connecting a third capacitor and a fourth capacitor in series and then connecting them in parallel with a variable inductor, and the series point of the third capacitor and the fourth capacitor is grounded.

16. The ac small-signal driving information pickup circuit according to any one of claims 9 to 12, wherein in said information pickup circuit unit, said feedback network is constituted by a variable capacitor and a transformer, wherein one end of a first winding of the transformer is connected to one end of the variable capacitor and serves as an input terminal of the feedback network, and the other end of the first winding of the transformer is connected to the other end of the variable capacitor and is grounded; one end of the second winding of the transformer is grounded, and the other end of the transformer is used as the output end of the feedback network.