Variable gain amplifier circuit and variable gain amplifier method

Abstract

The present invention discloses a variable gain amplifier circuit and a variable gain amplifier method, wherein the variable gain amplifier circuit comprises an electronic switch, a feedback resistor, an operational amplifier and a low-pass filter, wherein the electronic switch and the feedback resistor are connected in series and grounded, wherein the operational amplifier has an inverting input terminal, a non-inverting input terminal and an output terminal, the inverting input terminal of the operational amplifier is connected to the feedback resistor, the output terminal of the operational amplifier is connected to the low-pass filter, the non-inverting input terminal of the operational amplifier can be input with an analog signal, wherein the variable gain amplifier circuit is a non-inverting proportional amplifier circuit, wherein the frequency of the PWM signal applied to the electronic switch is higher than the frequency of the analog signal input from the non-inverting input terminal of the operational amplifier, so as to realize the program-controlled amplification function of the analog signal.

Description

Technical Field

[0001] The present invention relates to the technical field of analog signal program-controlled amplification, and in particular to a variable gain amplification circuit and a variable gain amplification method, wherein the variable gain amplification circuit realizes program-controlled amplification function based on electronic switch PWM control. Background Art

[0002] Analog signals are information marked by continuously changing physical quantities. The amplitude, frequency, and phase of the signals have the characteristics of continuously changing with time, which makes analog signals widely used in actual production and life. Program-controlled amplification of analog signals is an important means of processing analog signals. The analog signal program-controlled amplification circuit in the prior art uses a program-controlled amplification chip for amplification. Although the analog signal program-controlled amplification circuit can realize the program-controlled amplification function of the analog signal, it has the defects of high chip cost and high circuit power consumption. Summary of the invention

[0003] In view of the defects existing in the prior art, the present invention provides a variable gain amplification circuit and a variable gain amplification method.

[0004] Specifically, the present invention relates to the following aspects:

[0005] One aspect of the present invention provides a variable gain amplifier circuit, which includes an electronic switch, a feedback resistor, an operational amplifier and a low-pass filter, wherein the electronic switch and the feedback resistor are connected in series and grounded, wherein the operational amplifier has an inverting input terminal, a non-inverting input terminal and an output terminal, the inverting input terminal of the operational amplifier is connected to the feedback resistor, the output terminal of the operational amplifier is connected to the low-pass filter, the non-inverting input terminal of the operational amplifier can be input with an analog signal, wherein the variable gain amplifier circuit is a non-inverting proportional amplifier circuit, wherein the frequency of the PWM signal applied to the electronic switch is higher than the frequency of the analog signal input from the non-inverting input terminal of the operational amplifier.

[0006] According to one embodiment of the present invention, the feedback resistor includes a first resistor and a second resistor, wherein one end of the first resistor is connected to one end of the electronic switch, the other end of the first resistor is connected to the inverting input terminal of the operational amplifier, the other end of the electronic switch is grounded, one end of the second resistor is connected to a node between the inverting input terminal of the operational amplifier and the first resistor, and the other end of the second resistor is connected to a node between the output terminal of the operational amplifier and the low-pass filter.

[0007] According to an embodiment of the present invention, the electronic switch is a MOS tube or a triode.

[0008] According to an embodiment of the present invention, the frequency of the PWM signal applied to the electronic switch is three times higher than the frequency of the analog signal input from the non-inverting input terminal of the operational amplifier.

[0009] According to one embodiment of the present invention, the electronic switch is a P-type signal MOS tube, wherein the highest frequency of the analog signal input from the non-inverting input terminal of the operational amplifier is f0, the frequency applied to the G pole of the MOS tube is a PWM signal with a frequency of f1=5f0 and a duty cycle of D, and the cut-off frequency of the low-pass filter is f c =(f0+f1) / 2, then the analog signal output by the low-pass filter is

[0010] Another aspect of the present invention provides a variable gain amplification method, which is applied to a variable gain amplification circuit, wherein the variable gain amplification method comprises the following steps:

[0011] (a) An electronic switch and a feedback resistor are connected in series and then grounded;

[0012] (b) connecting the feedback resistor to an inverting input terminal of an operational amplifier;

[0013] (c) connecting a low-pass filter to an output terminal of the operational amplifier to form the variable gain amplifier circuit, wherein the variable gain amplifier circuit is constructed as an in-phase proportional amplifier circuit;

[0014] (d) inputting an analog signal into a common-phase input terminal of the operational amplifier;

[0015] (e) applying a PWM signal having a frequency higher than that of the analog signal input from the non-inverting input terminal of the operational amplifier to the electronic switch to realize a program-controlled amplification function.

[0016] According to one embodiment of the present invention, in the above method, the feedback resistor includes a first resistor and a second resistor, wherein one end of the first resistor is connected to one end of the electronic switch, the other end of the first resistor is connected to the inverting input terminal of the operational amplifier, the other end of the electronic switch is grounded, one end of the second resistor is connected to a node between the inverting input terminal of the operational amplifier and the first resistor, and the other end of the second resistor is connected to a node between the output terminal of the operational amplifier and the low-pass filter.

[0017] According to an embodiment of the present invention, in the above method, the electronic switch is a MOS tube or a triode.

[0018] According to an embodiment of the present invention, in the above method, the frequency of the PWM signal applied to the electronic switch is three times higher than the frequency of the analog signal input from the non-inverting input terminal of the operational amplifier.

[0019] According to one embodiment of the present invention, in the above method, the electronic switch is a P-type signal MOS tube, wherein the highest frequency of the analog signal input from the non-inverting input terminal of the operational amplifier is f0, the frequency applied to the G pole of the MOS tube is a PWM signal with a frequency of f1=5f0 and a duty cycle of D, and the cut-off frequency of the low-pass filter is f c =(f0+f1) / 2, then the analog signal output by the low-pass filter is

[0020] One advantage of the variable gain amplifier circuit of the present invention is that the electronic switch and the operational amplifier are used to replace the existing programmable amplifier chip to reduce the cost of the variable gain amplifier circuit. In particular, compared with the prior art using a programmable amplifier chip, the cost of the variable gain amplifier circuit of the present invention can be reduced by 10 times.

[0021] An advantage of the variable gain amplifier circuit of the present invention is that the electronic switch and the operational amplifier are used to replace the existing programmable amplifier chip to reduce the power consumption of the variable gain amplifier circuit.

[0022] One advantage of the variable gain amplifier circuit of the present invention is that the electronic switch and the operational amplifier are used to replace the existing programmable amplifier chip to improve the reliability of the variable gain amplifier circuit. In harsh environments, the variable gain amplifier circuit of the present invention can also stably perform programmable amplification on analog signals.

[0023] One advantage of the variable gain amplifier circuit of the present invention is that the electronic switch and the operational amplifier are used to replace the existing programmable amplifier chip, so that the variable gain amplifier circuit can conveniently control the amplification factor of the analog signal. For example, the amplification factor of the analog signal can be controlled by controlling the duty cycle D of the PWM signal applied to the electronic switch. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic diagram of a variable gain amplifier circuit according to a preferred embodiment of the present invention.

[0025] Figure 2 2 is a schematic diagram of the application state of the variable gain amplifier circuit according to the above preferred embodiment of the present invention.

[0026] Figure 3It is a flow chart of a variable gain amplification method according to a preferred embodiment of the present invention. DETAILED DESCRIPTION

[0027] Before describing in detail any embodiment of the present invention, it should be understood that the present invention is not limited in its application to the construction and arrangement details of the components described below or illustrated in the following figures. The present invention can have other embodiments and can be practiced or carried out in various ways. In addition, it should be understood that the words and terms used here are for descriptive purposes and should not be considered restrictive. The use of "including", "comprising" or "having" and its variations herein is intended to cover the items and their equivalents and additional items displayed below. Unless otherwise specified or limited, the terms "install", "connect", "support" and "couple" and their variations are widely used and cover direct installation and indirect installation, connection, support and connection. In addition, "connect" and "couple" are not limited to physical or mechanical connections or connections.

[0028] Furthermore, on the first aspect, in the disclosure of the present invention, the orientation or positional relationship indicated by terms such as "longitudinal", "transverse", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" are based on the orientation or positional relationship shown in the accompanying drawings, which are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore the above terms cannot be understood as limitations on the present invention; on the second aspect, the term "one" should be understood as "at least one" or "one or more", that is, in one embodiment, the number of an element may be one, while in another embodiment, the number of the element may be multiple, and the term "one" cannot be understood as a limitation on the quantity.

[0029] With reference to the accompanying drawings of the present invention Figure 1 and Figure 2 A variable gain amplifier circuit according to a preferred embodiment of the present invention will be disclosed and explained in the following description, wherein the variable gain amplifier circuit comprises an electronic switch 10, a feedback resistor 20, an operational amplifier 30 and a low-pass filter 40.

[0030] Specifically, the operational amplifier 30 has an inverting input terminal 31, a non-inverting input terminal 32 and an output terminal 33, wherein the electronic switch 10 and the feedback resistor 20 are connected in series and grounded, the feedback resistor 20 is connected to the inverting input terminal 31 of the operational amplifier 30, and the output terminal 33 of the operational amplifier 30 is connected to the low-pass filter 40, wherein the variable gain amplifier circuit formed by the electronic switch 10, the feedback resistor 20, the operational amplifier 30 and the low-pass filter 40 is constructed as a non-inverting proportional amplifier circuit. An analog signal is allowed to be input through the non-inverting input terminal 32 of the operational amplifier 30, the electronic switch 10 is allowed to apply a PWM signal, and the frequency of the PWM signal applied to the electronic switch 10 is higher than the analog signal input from the non-inverting input terminal 32 of the operational amplifier 30, so that when the analog signal is output through the low-pass filter 40, the analog signal is linearly amplified, so that the variable gain amplifier circuit realizes the programmable amplification function of the analog signal.

[0031] Unlike the circuit of the prior art that uses a programmable amplifier chip to perform programmable amplification on an analog signal, the variable gain amplifier circuit of the present invention uses the electronic switch 10 and the operational amplifier 30 to replace the existing programmable amplifier chip. In this way, not only can the cost and power consumption of the variable gain amplifier circuit be reduced, in particular, compared with the prior art that uses a programmable amplifier chip, the cost of the variable gain amplifier circuit of the present invention can be reduced by 10 times, and the reliability of the variable gain amplifier circuit is improved. In harsh environments, the variable gain amplifier circuit of the present invention can also stably amplify analog signals. For example, when the sonar to which the variable gain amplifier circuit of the present invention is applied is used underwater, the variable gain amplifier circuit can also stably amplify the analog signal of the sonar to ensure that the sonar works reliably. In addition, the variable gain amplifier circuit of the present invention uses the electronic switch 10 and the operational amplifier 30 to replace the existing programmable amplifier chip, so that the variable gain amplifier circuit can conveniently control the amplification factor of the analog signal. For example, the amplification factor of the analog signal can be controlled by controlling the duty cycle D of the PWM signal applied to the electronic switch 10. It is worth mentioning that the specific type of the electronic switch 10 is not limited in the variable gain amplifier circuit of the present invention. For example, in some embodiments of the variable gain amplifier circuit of the present invention, the electronic switch 10 may be a MOS tube, and in other embodiments of the variable gain amplifier circuit of the present invention, the electronic switch 10 may be a triode. Optionally, other components that are controlled by electrical signals may also be implemented as the electronic switch 10 of the variable gain amplifier circuit of the present invention.

[0032] Continue to refer to the attached Figure 1 The feedback resistor 20 includes a first resistor 21 and a second resistor 22. One end of the first resistor 21 is connected to one end of the electronic switch 10, and the other end of the electronic switch 20 is grounded, so that the electronic switch 10 and the feedback resistor 20 are connected in series, and the electronic switch 10 and the feedback resistor 20 after the series connection are grounded, and the other end of the first resistor 21 is connected to the inverting input terminal 31 of the operational amplifier 30, so as to connect the feedback resistor 20 to the inverting input terminal 31 of the operational amplifier 30. One end of the second resistor 22 is connected to the node between the inverting input terminal 31 of the operational amplifier 30 and the first resistor 21, and the other end of the second resistor 32 is connected to the node between the output terminal 33 of the operational amplifier 30 and the low-pass filter 40. Through the above-mentioned connection relationship, the electronic switch 10 and the feedback resistor 20 can be connected in series and grounded, and the variable gain amplifier circuit formed by the electronic switch 10, the feedback resistor 20, the operational amplifier 30 and the low-pass filter 40 is a common-phase proportional amplifier circuit, so that when an analog signal is input from the common-phase input terminal 32 of the operational amplifier 30, by applying a PWM signal having a frequency higher than the frequency of the analog signal input from the common-phase input terminal 32 of the operational amplifier 30 to the electronic switch 10, the analog signal output from the low-pass filter 40 can be linearly amplified, thereby realizing the programmable amplification function of the analog signal.

[0033] Preferably, in a specific example of the variable gain amplifier circuit of the present invention, the frequency of the PWM signal applied to the electronic switch 10 is higher than three times the frequency of the analog signal input from the non-inverting input terminal 32 of the operational amplifier 30 .

[0034] In a specific example of the variable gain amplifier circuit of the present invention, the electronic switch 10 is a P-type signal MOS tube, wherein the highest frequency of the analog signal input from the in-phase input terminal 32 of the operational amplifier 30 is f0, and the frequency applied to the G pole of the MOS tube is a PWM signal with a frequency of f1=5f0 and a duty cycle of D, and the cut-off frequency of the low-pass filter 40 is fc=(f0+f1) / 2, then the analog signal output by the low-pass filter 40 is It can be seen that the amplification factor of the analog signal output from the low-pass filter 40 changes linearly with the duty cycle D of the PWM signal applied to the electronic switch 10, so the amplification factor of the analog signal can be controlled by controlling the duty cycle D of the PWM signal applied to the electronic switch 10.

[0035] Specifically, assuming that the input analog signal is x(t) and the frequency band is f L ~f H , when the electronic switch 10 is closed, the maximum gain of the variable gain amplifier circuit is The PWM signal for controlling the electronic switch 10 is u(t), which is a square wave, wherein a value of 1 indicates that the electronic switch 10 is closed, and a value of 0 indicates that the electronic switch 10 is open. The frequency of the PWM signal is f0, and the duty cycle is D. Then, the analog signal output by the electronic switch 10 is expressed as:

[0036] y(t)=G max x(t)u(t)+x(t)(1-u(t)) (1)

[0037] After finishing, we can get:

[0038]

[0039] The Fourier series analysis of u(t) is:

[0040]

[0041] Where D is the constant term, i.e. duty cycle, and ú(t) is the AC term, then:

[0042]

[0043] in It is called the low-frequency term. It can be seen that the relationship between this low-frequency term and the input x(t) is linear, and its amplitude is x(t). times, which is controlled by the duty cycle D.

[0044] It is called the high frequency term, which is equivalent to moving the spectrum of x(t) upward. This only requires sending y(t) to the cutoff frequency at f H The low-pass filter between f0 and f0 can obtain the low-frequency term y L (t), thereby achieving the purpose of controlling by using the electronic switch 10, the effect is as follows Figure 2 shown.

[0045] Reference Figure 3 According to another aspect of the present invention, the present invention further provides a variable gain amplification method 300, which is applied to a variable gain amplification circuit, wherein the variable gain amplification method 300 comprises the following steps:

[0046] Step 310, connecting the electronic switch 10 and the feedback resistor 20 in series and then grounding them;

[0047] Step 320, connecting the feedback resistor 20 to the inverting input terminal 31 of the operational amplifier 30;

[0048] Step 330, connecting the low-pass filter 40 to the output terminal 33 of the operational amplifier 30 to form the variable gain amplifier circuit, wherein the variable gain amplifier circuit is constructed as an in-phase proportional amplifier circuit;

[0049] Step 340, inputting an analog signal into the non-inverting input terminal 32 of the operational amplifier 30;

[0050] Step 350 , applying a PWM signal having a frequency higher than the analog signal input from the non-inverting input terminal 32 of the operational amplifier 30 to the electronic switch 10 , so as to realize a program-controlled amplification function.

[0051] It should be understood by those skilled in the art that the embodiments of the present invention described above and shown in the accompanying drawings are only examples and do not limit the present invention. The purpose of the present invention has been fully and effectively achieved. The functional and structural principles of the present invention have been demonstrated and explained in the embodiments, and the embodiments of the present invention may be deformed or modified in any way without departing from the principles.

Claims

1. A variable gain amplifier circuit, characterized in that: The invention comprises an electronic switch, a feedback resistor, an operational amplifier and a low-pass filter, wherein the electronic switch and the feedback resistor are connected in series and grounded, wherein the operational amplifier has an inverting input terminal, a non-inverting input terminal and an output terminal, the inverting input terminal of the operational amplifier is connected to the feedback resistor, the output terminal of the operational amplifier is connected to the low-pass filter, the non-inverting input terminal of the operational amplifier can be input with an analog signal, wherein the variable gain amplifier circuit is a non-inverting proportional amplifier circuit, wherein the frequency of the PWM signal applied to the electronic switch is higher than the frequency of the analog signal input from the non-inverting input terminal of the operational amplifier; wherein the feedback resistor comprises a first resistor and a second resistor, wherein one end of the first resistor is connected to one end of the electronic switch, the other end of the first resistor is connected to the inverting input terminal of the operational amplifier, the other end of the electronic switch is grounded, one end of the second resistor is connected to a node between the inverting input terminal of the operational amplifier and the first resistor, and the other end of the second resistor is connected to a node between the output terminal of the operational amplifier and the low-pass filter; The analog signal input is , the frequency band is , when the electronic switch is closed, the maximum gain of the variable gain amplifier circuit is , the PWM signal controlling the electronic switch is , is a square wave, when the value is 1, the electronic switch is closed, when the value is 0, the electronic switch is open, and the duty cycle is , then the expression of the analog signal output by the electronic switch control is: ； After finishing, we can get: ； right The Fourier series analysis of is: ； in is the duty cycle constant term, is an exchange term, then: ； in is a low-frequency term, which is related to the input analog signal is a linear relationship, and its amplitude is of times, which is related to the duty cycle Related, among them is a high frequency term, which The spectrum of The cut-off frequency is and The low-pass filter between the two can obtain the low-frequency term , realizing control by utilizing the electronic switch. 2 . The variable gain amplifier circuit according to claim 1 , wherein the electronic switch is a MOS tube or a triode.

3. The variable gain amplifier circuit according to claim 1, wherein the frequency of the PWM signal applied to the electronic switch is higher than three times the frequency of the analog signal input from the non-inverting input terminal of the operational amplifier.

4. The variable gain amplifier circuit according to claim 1, wherein the electronic switch is a P-type signal MOS tube, wherein the maximum frequency of the analog signal input from the non-inverting input terminal of the operational amplifier is The frequency applied to the G pole of the MOS tube is , a PWM signal with a duty cycle of D, the cut-off frequency of the low-pass filter is , then the analog signal output by the low-pass filter is .

5. A variable gain amplification method, applied to a variable gain amplification circuit, characterized in that: The variable gain amplification method comprises the following steps: (a) An electronic switch and a feedback resistor are connected in series and then grounded; (b) connecting the feedback resistor to an inverting input terminal of an operational amplifier; (c) connecting a low-pass filter to an output terminal of the operational amplifier to form the variable gain amplifier circuit, wherein the variable gain amplifier circuit is constructed as an in-phase proportional amplifier circuit; (d) inputting an analog signal into a common-phase input terminal of the operational amplifier; (e) applying a PWM signal having a frequency higher than that of the analog signal input from the non-inverting input terminal of the operational amplifier to the electronic switch to realize a program-controlled amplification function; Wherein in the above method, the feedback resistor includes a first resistor and a second resistor, wherein one end of the first resistor is connected to one end of the electronic switch, the other end of the first resistor is connected to the inverting input terminal of the operational amplifier, the other end of the electronic switch is grounded, one end of the second resistor is connected to a node between the inverting input terminal of the operational amplifier and the first resistor, and the other end of the second resistor is connected to a node between the output terminal of the operational amplifier and the low-pass filter; The analog signal input is , the frequency band is , when the electronic switch is closed, the maximum gain of the variable gain amplifier circuit is , the PWM signal controlling the electronic switch is , is a square wave, when the value is 1, the electronic switch is closed, when the value is 0, the electronic switch is open, and the duty cycle is , then the expression of the analog signal output by the electronic switch control is: ； After finishing, we can get: ； right The Fourier series analysis of is: ； in is the duty cycle constant term, is an exchange term, then: ； in is a low-frequency term, which is related to the input analog signal is a linear relationship, and its amplitude is of times, which is related to the duty cycle Related, among them is a high frequency term, which The spectrum of The cut-off frequency is and The low-pass filter between the two can obtain the low-frequency term , realizing control by utilizing the electronic switch. 6 . The variable gain amplification method according to claim 5 , wherein in the above method, the electronic switch is a MOS tube or a triode.

7. The variable gain amplification method according to claim 5, wherein in the above method, the frequency of the PWM signal applied to the electronic switch is higher than three times the frequency of the analog signal input from the non-inverting input terminal of the operational amplifier.

8. The variable gain amplification method according to claim 5, wherein in the above method, the electronic switch is a P-type signal MOS tube, wherein the maximum frequency of the analog signal input from the non-inverting input terminal of the operational amplifier is The frequency applied to the G pole of the MOS tube is , a PWM signal with a duty cycle of D, the cut-off frequency of the low-pass filter is , then the analog signal output by the low-pass filter is .

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