CN218941059U - Automatic gain circuit, automatic gain device and audio power amplifier - Google Patents
Automatic gain circuit, automatic gain device and audio power amplifier Download PDFInfo
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Abstract
The utility model belongs to the field of audio power amplifiers, and provides an automatic gain circuit, an automatic gain device and an audio power amplifier, wherein the automatic gain circuit comprises a gain module, an input resistance module and a comparison control module, the input resistance module is connected with the input end of the gain module, the comparison control module compares a gain output signal with a preset voltage threshold range, and generates a gain adjusting signal according to a comparison result.
Description
Technical Field
The application belongs to the field of audio power amplifiers, and particularly relates to an automatic gain circuit, an automatic gain device and an audio power amplifier.
Background
In daily life, the audio power amplifier is an indispensable component in the acoustic equipment such as headphones and radios, and the audio power amplifier mainly amplifies input signals through a gain amplifying circuit, for example, the received signals in the radio equipment are amplified and output to a loudspeaker for playing, the amplifying function of the general audio power amplifier can be performed by an automatic gain circuit, and the automatic gain circuit adjusts the amplifying times of the automatic gain circuit by using the voltage output by the operational amplifier.
However, the adjusting resistor in the automatic gain circuit is affected by factors such as matching precision and loop stability, and there is a problem that the adjustable range is limited, which is unfavorable for amplifying the input signal.
Disclosure of Invention
The utility model provides an automatic gain circuit, an automatic gain device and an audio power amplifier, and aims to solve the problems that an adjustable range of the automatic gain circuit is limited and amplification of an input signal is not facilitated.
A first aspect of an embodiment of the present application provides an automatic gain circuit, including:
the gain module is used for amplifying the input signal and generating a gain output signal;
the input resistor module is connected with the input end of the gain module;
and the comparison control module is connected with the gain adjustment module and the input resistance module and is used for receiving the gain output signal and outputting a gain adjustment signal to the input resistance module according to the gain output signal so as to adjust the resistance of the input resistance module.
In one embodiment, the gain module comprises:
the non-inverting input end of the operational amplifier is connected with the input resistor module, and the inverting input end of the operational amplifier is connected with a bias signal source;
and the first end of the feedback resistance unit is connected with the non-inverting input end of the operational amplifier, and the second end of the feedback resistance unit is connected with the output end of the operational amplifier.
In one embodiment, the feedback resistance unit comprises at least one resistor, the at least one resistor being connected in series.
In one embodiment, the input resistance module includes: the first capacitor, the first resistor, the second resistor and the adjustable resistor;
the first end of the first capacitor is connected with an input signal source, the second end of the first capacitor is connected with the first end of the first resistor, the second end of the first resistor and the first end of the adjustable resistor are connected with the first end of the second resistor in a sharing mode, the second end of the second resistor is connected with the gain module, the second end of the adjustable resistor is connected with a bias signal source, and the control end of the adjustable resistor is connected with the comparison control module.
In one embodiment, a resistor adjusting module is further arranged between the adjustable resistor and the comparison control module, and the resistor adjusting module is used for adjusting the position of the control end of the adjustable resistor according to the gain adjusting signal.
In one embodiment, the bias signal source is a ground signal source.
In one embodiment, the comparison control module includes a first comparator, a second comparator, a first nand gate;
the inverting input end of the first comparator and the non-inverting input end of the second comparator are connected with the output end of the gain module, the non-inverting input end of the first comparator is connected with a first threshold voltage source, the inverting input end of the second comparator is connected with a second threshold voltage source, the first input end of the first NAND gate is connected with the output end of the first comparator, the second input end of the first NAND gate is connected with the output end of the second comparator, and the output end of the first NAND gate is connected with the input resistor module.
In one embodiment, the first threshold voltage source provides a first threshold voltage having a voltage value that is greater than a voltage value of the second threshold voltage provided by the second threshold voltage source.
A second aspect of the present embodiment provides an automatic gain apparatus comprising an automatic gain circuit of any one of the above.
The present application finally provides an audio power amplifier comprising an automatic gain circuit of any of the above.
The automatic gain circuit comprises a gain module, an input resistance module and a comparison control module, wherein the input resistance module is connected with the input end of the gain module, the comparison control module compares a gain output signal with a preset voltage threshold range, a gain adjusting signal is generated according to a comparison result and is used for adjusting the resistance value of the input resistance module, the resistance value of the input resistance module is in negative correlation with the amplification factor of the gain module, the amplification factor of the gain module can be adjusted by adjusting the resistance value of the input resistance module, and the adjustable range of the gain module can be expanded due to the fact that the input resistance module is independent of the gain module, and the problem that the automatic gain circuit is slow in feedback is solved.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are needed in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present application, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a functional block diagram of an automatic gain circuit according to an embodiment of the present application;
fig. 2 is a schematic circuit diagram of a gain module according to an embodiment of the present disclosure;
fig. 3 is a schematic circuit diagram of an input resistor module according to an embodiment of the present application;
fig. 4 is a schematic circuit diagram of a comparison control module according to an embodiment of the present application;
fig. 5 is a schematic circuit diagram of an automatic gain circuit according to an embodiment of the present application.
Detailed Description
In order to make the technical problems, technical schemes and beneficial effects to be solved by the present application more clear, the present application is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the present application.
It will be understood that when an element is referred to as being "mounted" or "disposed" on another element, it can be directly on the other element or be indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or be indirectly connected to the other element.
It is to be understood that the terms "length," "width," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," and the like indicate or are based on the orientation or positional relationship shown in the drawings, merely to facilitate description of the present application and simplify description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be configured and operated in a particular orientation, and therefore should not be construed as limiting the present application.
Furthermore, the terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include one or more such feature. In the description of the present application, the meaning of "a plurality" is two or more, unless explicitly defined otherwise.
The simplest open loop circuit comprises an operational amplifier, an input signal is input from a non-inverting input end or an inverting input end of the operational amplifier, the other end is grounded or a bias signal is input, differential signals of the input signal and the bias signal are output from an output end of the operational amplifier after being subjected to gain, the open loop differential gain of the input signal is generally determined by the operational amplifier, and even if the differential signal at the output end is small, the output signal is still saturated, so that nonlinear distortion occurs, and the amplification of the input signal is not favored.
In order to prevent the output end of the gain circuit from generating distortion signals, in headphones and sound equipment used in daily life, a general gain circuit works in a closed loop amplifier mode, an input resistor and a feedback resistor are added on the basis of an operational amplifier to form a closed loop, the input signal is connected with one input end of the operational amplifier through the input resistor, the other input end is grounded or connected with bias voltage, the feedback resistor is connected in parallel with the input end of the input signal of the operational amplifier and the output end of the operational amplifier, and the output voltage of the gain circuit is as follows: vout=rf=vin/Rin, where Rin is the resistance of the input resistor, rf is the resistance of the feedback resistor, and the gain effect of the gain circuit can be adjusted by adjusting the resistance of the input resistor or the feedback resistor.
The output signal is generally regulated by adopting a mode of regulating the resistance value of the feedback resistor, but the feedback resistor is influenced by the matching precision of the resistor and the stability of the closed-loop amplifier circuit, the adjustable range of the resistance value of the feedback resistor is smaller, and the distortion caused by the fact that the input signal is too large or the gain is too large can not be effectively controlled when the output signal is seriously distorted.
In order to solve the above technical problems, an embodiment of the present application provides an automatic gain circuit, and fig. 1 is a functional block diagram of the automatic gain circuit provided in the embodiment of the present application, and, with reference to fig. 1, the automatic gain circuit in the embodiment includes a gain module 101, an input resistor module 102, and a comparison control module 103.
The gain module 101 is configured to amplify an input signal Vin and output a gain output signal Vout at an output terminal; the input resistor module 102 is connected with the input end of the gain module 101; the comparison control module 103 is connected to the gain module 101 and the input resistor module 102, where the comparison control module 103 is configured to receive the gain output signal Vout, generate a gain adjustment signal Vc according to the gain output signal Vout, and output the gain adjustment signal Vc to the input resistor module 102 to adjust a resistance value of the input resistor module 102, and if the gain adjustment signal Vc is, for example, a high level, the gain adjustment signal Vc controls the resistance value of the input resistor module 102 to decrease, and if the gain adjustment signal Vc is a low level, the gain adjustment signal Vc controls the resistance value of the input resistor module 102 to increase, and the resistance value of the input resistor module 102 is inversely related to an amplification factor of the gain module 101.
Specifically, in this embodiment, the input end of the input resistor module 102 is connected to an input signal source that generates an input signal Vin, the input signal Vin is amplified by the gain module 101 to generate a gain output signal Vout, and the gain output signal Vout is output from the output end of the gain module 101, where the gain multiple of the input signal Vin is determined by the input resistor module 102 and the gain module 101 together, the comparison control module 103 receives the gain output signal Vout output from the gain module 101 and compares the gain output signal Vout with a preset voltage threshold range, and generates a gain adjustment signal Vc according to the comparison result, and the gain adjustment signal Vc controls the resistance value of the input resistor module 102, so as to control the gain of the input signal Vin.
In one embodiment, gain module 101 includes an operational amplifier N3 and a feedback resistor unit 1011.
Specifically, referring to fig. 2, the non-inverting input terminal of the operational amplifier N3 is connected to the input resistor module 102, and the inverting input terminal of the operational amplifier N3 is connected to the bias signal source; a first end of the feedback resistor unit 1011 is connected to the non-inverting input terminal of the operational amplifier N3, and a second end of the feedback resistor unit 1011 is connected to the output terminal of the operational amplifier N3.
In one embodiment, feedback resistor unit 1011 includes at least one resistor connected in series.
For example, referring to fig. 2, the feedback resistor unit 1011 includes a feedback resistor Rf, the non-inverting input terminal of the operational amplifier N3 is connected to the input resistor module 102 and the first terminal of the feedback resistor Rf, the inverting input terminal of the operational amplifier N3 is connected to a bias signal source generating a bias signal Verf, and the output terminal of the operational amplifier N3 is connected to the second terminal of the feedback resistor Rf.
In this embodiment, the input signal Vin first passes through the input resistor module 102, and because the voltage of the input signal Vin and the voltage of the inverting input terminal of the operational amplifier are inconsistent, there is a potential difference between the input terminal and the output terminal of the input resistor module 102, the input signal Vin will generate a current on the input resistor module 102 and flow through the input resistor module 102, and because the input impedance of the operational amplifier N3 is infinite, no current flows through the operational amplifier N3, and thus a current will flow through the feedback resistor Rf and generate a voltage on the feedback resistor Rf, and the voltage generated on the feedback resistor Rf is determined by the input resistor module 102 and the feedback resistor Rf together.
In one embodiment, referring to FIG. 3, the input resistance module 102 includes: the first capacitor C1, the first resistor R1, the second resistor R2 and the adjustable resistor Rc.
Specifically, a first end of the first capacitor C1 is connected to the input signal source, a second end of the first capacitor C1 is connected to a first end of the first resistor R1, a second end of the first resistor R1 and a first end of the adjustable resistor Rc are commonly connected to a first end of the second resistor R2, a second end of the second resistor R2 is connected to the gain module 101, a second end of the adjustable resistor Rc is connected to the bias signal source that generates the bias signal Vref, a control end of the adjustable resistor Rc is connected to the comparison control module 103, and the gain adjustment signal Vc is used to control a resistance value of the adjustable resistor Rc.
In this embodiment, the input signal Vin first passes through the first capacitor C1, the first capacitor C1 acts as a dc voltage isolation device to isolate the dc voltage in the input signal Vin, so as to prevent the dc voltage from affecting the automatic gain circuit, the input signal Vin is input to the gain module 101 after passing through the first resistor R1, the second resistor R2 and the adjustable resistor Rc, and the input signal Vin generates a current in the input resistor module 102 and is input to the gain module 101 due to inconsistent voltages at two ends of the input resistor module 102, wherein the resistance value of the input resistor module 102 is determined by the first resistor R1, the second resistor R2 and the adjustable resistor Rc, and the gain effect of the automatic gain circuit is determined by the first resistor R1, the second resistor R2, the adjustable resistor Rc and the feedback resistor Rf.
Preferably, the adjustable resistor Rc can adjust its own resistance value by means of switch gating, and a resistor adjusting module is arranged between the adjustable resistor Rc and the comparison control module 103, and the resistor adjusting module can adjust the position of the control end of the adjustable resistor Rc according to the gain adjusting signal Vc.
In one embodiment, the bias signal source is a ground signal source or a predetermined bias signal source.
In one embodiment, the comparison control module 103 includes a first comparator N1, a second comparator N2, and a first nand gate D1.
Specifically, referring to fig. 4, the inverting input terminal of the first comparator N1 and the non-inverting input terminal of the second comparator N2 are commonly connected to the output terminal of the gain module 101, the non-inverting input terminal of the first comparator N1 is connected to a first threshold voltage source for providing the first threshold voltage V1, the inverting input terminal of the second comparator N2 is connected to a second threshold voltage source for providing the second threshold voltage V2, the first terminal of the first nand gate D1 is connected to the output terminal of the first comparator N1, the second terminal of the first nand gate D1 is connected to the output terminal of the second comparator N2, and the output terminal of the first nand gate D1 is connected to the input resistor module 102.
In this embodiment, the inverting input terminal of the first comparator N1 is connected to the output terminal of the gain module 101, the non-inverting input terminal of the first comparator N1 is input with the first threshold voltage V1, the output terminal of the first comparator N1 is connected to the first input terminal of the first nand gate D1, the non-inverting input terminal of the second comparator N2 is connected to the output terminal of the gain module 101, the inverting input terminal of the second comparator N2 is input with the second threshold voltage V2, the output terminal of the second comparator N2 is connected to the second input terminal of the first nand gate D1, the output terminal of the first nand gate D1 is connected to the input resistor module 102, and the output terminal of the first nand gate D1 outputs the gain adjustment signal Vc.
In the present embodiment, the gain output signal Vout output by the gain module 101 is compared with the first threshold voltage V1 and the second threshold voltage V2 through the first comparator N1 and the second comparator N2, respectively.
The gain output signal Vout is input to the inverting input terminal of the first comparator N1 and is compared with the first threshold voltage V1, meanwhile, the gain output signal Vout is input to the non-inverting input terminal of the second comparator N2 and is compared with the second threshold voltage V2, when the voltage value of the gain output signal Vout is greater than the first threshold voltage V1, the first comparator V1 outputs a low level, when the voltage value of the gain output signal Vout is less than the first threshold voltage V1, the first comparator V1 outputs a high level, and when the voltage value of the gain output signal Vout is greater than the second threshold voltage V2, the second comparator N2 outputs a high level.
When the voltage value of the gain output signal Vout is smaller than the first threshold voltage V1, the first comparator V1 outputs a high level, and when the voltage value of the gain output signal Vout is larger than the second threshold voltage V2, the second comparator N2 outputs a high level gain adjustment signal Vc, at this time, the gain adjustment signal Vc does not adjust the resistance value of the adjustable resistor Rc, that is, when V1 > Vout > V2, it indicates that the gain multiple of the self-gain circuit is within a preset range, and the voltage value of the gain output signal Vout is within a preset voltage threshold range, and does not adjust the gain multiple of the self-gain circuit.
When the first comparator N1 outputs a low level and/or the second comparator N2 outputs a low level, the first nand gate D1 outputs a high-level gain adjustment signal Vc, and at this time, the gain adjustment signal Vc adjusts the resistance value of the adjustable resistor Rc, so as to achieve the purpose of adjusting the resistance value of the input resistor module 102, for example, by reducing the resistance value of the adjustable resistor Rc, further reducing the gain multiple, and ensuring that the voltage value of the gain output signal Vout is within the preset voltage threshold range, so as to avoid distortion of the gain output signal Vout.
Specifically, in one practical embodiment, the gain of the automatic gain circuit is a gain multiple of vout=vin (r2+rc) ×rf/[ r2×rc+r1 (r2+rc) ]: when V1 > Vout > V2, both the first comparator V1 output and the second comparator N2 output a high level, and the gain adjustment signal Vc is at a low level, which indicates that the gain multiple of the self-gain circuit is within a preset range, and the voltage value of the gain output signal Vout is within a preset voltage threshold range, and the gain multiple of the self-gain circuit is not adjusted.
In this embodiment, since the adjustable resistor Rc is disposed at the input end of the gain module 101, and the feedback resistor Rf is relatively sensitive in the whole circuit, the adjustable range of the feedback resistor Rf is limited due to the influence of the matching precision and the loop stability of the resistor, and the adjustable resistor Rc is disposed at the input end of the gain module 101, so that the influence on the matching of the resistor and the loop stability is small, and meanwhile, the adjustable range of the gain module 101 is increased, and the design reliability and stability of the self-gain circuit are improved.
In one embodiment, the first threshold voltage V1 may be a maximum voltage value output by the preset automatic gain circuit, and the second threshold voltage V2 may be a minimum voltage value output by the preset automatic gain circuit, and the first threshold voltage V1 is greater than the second threshold voltage V2.
In this embodiment, to prevent distortion caused by the voltage gain exceeding the power supply range after the input signal Vin passes through the automatic gain circuit, the first threshold voltage V1 and the second threshold voltage V2 need to be adjusted in combination with the input signal Vin, wherein the first threshold voltage V1 and the second threshold voltage V2 do not exceed the power supply allowable range.
In one embodiment, the first comparator N1 and the second comparator N2 may be operational amplifiers or comparison circuits having the same structure.
Fig. 5 is a schematic diagram of an automatic gain circuit, in which an input signal Vin sequentially passes through a first capacitor C1, a first resistor R1, a second resistor R2 and an adjustable resistor Rc and then enters a gain module 101, a feedback resistor Rf in the gain module 101 is used for providing effective gain for the input signal Vin, an inverting input terminal of an operational amplifier N3 is connected with a bias voltage Vref, which causes a non-inverting input terminal of the operational amplifier N3 to have the same voltage value as the inverting input terminal, so that a voltage difference is generated between two ends of the input resistor module 102, and thus a current flows through the input resistor module 102, and the input resistor of the operational amplifier N3 is large, so that the current flowing through the input resistor module 102 reaches an output terminal of the operational amplifier N3 through the feedback resistor Rf, and a voltage is generated between two ends of the feedback resistor Rf when the current passes through the feedback resistor Rf, and the voltage is the gain voltage of the input signal Vin.
Since the gain output signal Vout after gain has distortion, the gain effect of the automatic gain circuit needs to be determined according to the gain output signal Vout, the gain output signal Vout is transmitted to the first nand gate D1 after passing through the first comparator N1 and the second comparator N2, if the gain output signal Vout has distortion, the first nand gate D1 outputs a high level to the adjustable resistor Rc, and the adjustable resistor Rc reduces the resistance value of the adjustable resistor Rc through a mode of switching and tuning, thereby reducing the gain effect of the automatic gain circuit, if the gain output signal Vout does not have distortion, the first nand gate D1 outputs a low level to the adjustable resistor Rc, the resistance value of the adjustable resistor Rc remains unchanged, and the gain effect of the automatic gain circuit remains unchanged.
In one embodiment, operational amplifier N3 may be replaced with a fully differential amplifying circuit.
The gain module 101 is configured to amplify an input signal Vin to generate a gain output signal Vout with an increasing effect, the input resistor module 102 is connected to an input end of the gain module 101, and is capable of automatically adjusting an input resistor Rc and controlling an amplification factor of an automatic gain circuit, the comparison control module 103 is connected to the gain module 101 and the input resistor module 102, and is configured to receive the gain output signal Vout, output a gain adjustment signal Vc to the input resistor module 102 according to the gain output signal Vout, adjust a resistance value of the input resistor module 102, and the input resistor module 102 is a resistance adjustment module independent of the gain module 101, and has a small influence on an adjustable range by the automatic gain circuit, and meanwhile, improve an adjustable range of the automatic gain circuit and solve a problem that feedback of the automatic gain circuit is slow.
The embodiment of the application also provides an automatic gain device, which comprises the automatic gain circuit in any one of the embodiments.
The embodiment of the application finally provides an audio power amplifier, which comprises the automatic gain circuit according to any one of the embodiments.
It will be apparent to those skilled in the art that, for convenience and brevity of description, only the above-described division of the functional units and modules is illustrated, and in practical application, the above-described functional distribution may be performed by different functional units and modules according to needs, i.e. the internal structure of the apparatus is divided into different functional units or modules to perform all or part of the above-described functions. The functional units and modules in the embodiment may be integrated in one processing unit, or each unit may exist alone physically, or two or more units may be integrated in one unit, where the integrated units may be implemented in a form of hardware or a form of a software functional unit. In addition, specific names of the functional units and modules are only for convenience of distinguishing from each other, and are not used for limiting the protection scope of the present application. The specific working process of the units and modules in the above system may refer to the corresponding process in the foregoing method embodiment, which is not described herein again.
In the foregoing embodiments, the descriptions of the embodiments are emphasized, and in part, not described or illustrated in any particular embodiment, reference is made to the related descriptions of other embodiments.
The units described as separate units may or may not be physically separate, and units shown as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.
In addition, each functional unit in each embodiment of the present application may be integrated in one processing unit, or each unit may exist alone physically, or two or more units may be integrated in one unit. The integrated units may be implemented in hardware or in software functional units.
The above embodiments are only for illustrating the technical solution of the present application, and are not limiting; although the present application has been described in detail with reference to the foregoing embodiments, it should be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit and scope of the technical solutions of the embodiments of the present application, and are intended to be included in the scope of the present application.
Claims (10)
1. An automatic gain circuit, the automatic gain circuit comprising:
the gain module is used for amplifying the input signal and generating a gain output signal;
the comparison control module is connected with the gain adjustment module and is used for receiving the gain output signal, comparing the gain output signal with a preset voltage threshold range and generating a gain adjustment signal according to a comparison result;
the input resistor module is connected with the input end of the gain module;
the gain adjusting signal is used for adjusting the resistance of the input resistor module, and the resistance of the input resistor module is inversely related to the amplification factor of the gain module.
2. The automatic gain circuit of claim 1 wherein the gain module comprises:
the non-inverting input end of the operational amplifier is connected with the input resistor module, and the inverting input end of the operational amplifier is connected with a bias signal source;
and the first end of the feedback resistance unit is connected with the non-inverting input end of the operational amplifier, and the second end of the feedback resistance unit is connected with the output end of the operational amplifier.
3. The automatic gain circuit of claim 2 wherein the feedback resistance unit comprises at least one resistor, the at least one resistor being connected in series.
4. The automatic gain circuit of claim 1 wherein the input resistance module comprises: the first capacitor, the first resistor, the second resistor and the adjustable resistor;
the first end of the first capacitor is connected with an input signal source, the second end of the first capacitor is connected with the first end of the first resistor, the second end of the first resistor and the first end of the adjustable resistor are connected with the first end of the second resistor in a sharing mode, the second end of the second resistor is connected with the gain module, the second end of the adjustable resistor is connected with a bias signal source, and the control end of the adjustable resistor is connected with the comparison control module.
5. The automatic gain circuit of claim 4, wherein a resistor adjustment module is further disposed between the adjustable resistor and the comparison control module, and the resistor adjustment module is configured to adjust a position of a control end of the adjustable resistor according to the gain adjustment signal.
6. The automatic gain circuit of claim 2 or 4 wherein the bias signal source is a ground signal source.
7. The automatic gain circuit of claim 1 wherein the comparison control module comprises: a first comparator, a second comparator, a first NAND gate;
the inverting input end of the first comparator and the non-inverting input end of the second comparator are connected with the output end of the gain module, the non-inverting input end of the first comparator is connected with a first threshold voltage source, the inverting input end of the second comparator is connected with a second threshold voltage source, the first input end of the first NAND gate is connected with the output end of the first comparator, the second input end of the first NAND gate is connected with the output end of the second comparator, and the output end of the first NAND gate is connected with the input resistor module.
8. The automatic gain circuit of claim 7 wherein a voltage value of a first threshold voltage provided by the first threshold voltage source is greater than a voltage value of the second threshold voltage provided by the second threshold voltage source.
9. An automatic gain apparatus comprising an automatic gain circuit according to any one of claims 1 to 8.
10. An audio power amplifier comprising an automatic gain circuit according to any of claims 1-8.
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| CN202122522069.9U CN218941059U (en) | 2021-10-19 | 2021-10-19 | Automatic gain circuit, automatic gain device and audio power amplifier |
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| CN202122522069.9U CN218941059U (en) | 2021-10-19 | 2021-10-19 | Automatic gain circuit, automatic gain device and audio power amplifier |
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