CN102201792A - Automatic gain control circuit of audio power amplifier - Google Patents

Automatic gain control circuit of audio power amplifier Download PDF

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Publication number
CN102201792A
CN102201792A CN2010101326397A CN201010132639A CN102201792A CN 102201792 A CN102201792 A CN 102201792A CN 2010101326397 A CN2010101326397 A CN 2010101326397A CN 201010132639 A CN201010132639 A CN 201010132639A CN 102201792 A CN102201792 A CN 102201792A
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CN
China
Prior art keywords
operational amplifier
circuit
output
control circuit
input
Prior art date
Application number
CN2010101326397A
Other languages
Chinese (zh)
Inventor
肖国庆
蒋锦茂
Original Assignee
上海沙丘微电子有限公司
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by 上海沙丘微电子有限公司 filed Critical 上海沙丘微电子有限公司
Priority to CN2010101326397A priority Critical patent/CN102201792A/en
Publication of CN102201792A publication Critical patent/CN102201792A/en

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Abstract

The invention discloses an automatic gain control circuit of an audio power amplifier, which comprises a fully differential operational amplifier and an automatic gain control circuit, wherein the in-phase and anti-phase input ends of the amplifier are provided with divider resistors respectively; feedback resistors are arranged between the in-phase input end and an output end as well as between the in-phase input end and the output end respectively; a biasing circuit is connected the fully differential operational amplifier; the input end of the control circuit is connected with the output end of the fully differential operational amplifier; a reference voltage circuit is connected with the control circuit; and the output end of the control circuit is connected with an adjustable resistor at the input end of the fully differential operational amplifier. In the invention, an output signal is compared with a reference voltage to obtain a digital signal, and the digital signal is used for controlling the front resistance value of the input end of the amplifier, so that a fixed gain can be kept for amplifying an audio signal during inputting of a small signal, closed-loop gain in the circuit is reduced during inputting of a large audio signal, and high linearity and low harmonic distortion of an output audio signal are ensured.

Description

The audio-frequency power amplifier automatic gain control circuit

[technical field]

The present invention relates to the audio-frequency power amplifier in the extensive analog integrated circuit design field, particularly a kind of audio-frequency power amplifier automatic gain control circuit.

[background technology]

Fig. 1 is the circuit structure of power audio amplifier traditional in a kind of prior art, and in the sort circuit structure, audio signal is amplified through the fully differential operational amplifier.The output of audio signal changes with the variation of input, when importing big audio signal (Vi+ and Vi-are bigger), after this audio input signal amplifies through the fully differential operational amplifier, output Vo-, Vo+ is also bigger, thereby causes the output peakedness ratio of audio signal bigger, again this signal is carried out modulation and demodulation, then the signal after the demodulation can produce the top distortion, thereby causes big harmonic distortion amount, both poor sound quality.

Prior art increases the signal amplitude of input signal in order to overcome above-mentioned defective, guarantees that simultaneously the harmonic distortion amount is few, has mainly adopted and has improved supply voltage and the technical method that reduces the gain of fully differential operational amplifier in the circuit.Though increase the amplitude that power source voltage can increase the audio frequency input variable, this method can increase the design cost of circuit and consume big power consumption, also can introduce big noise simultaneously; Signal to noise ratio when the gain that reduces circuit can reduce the small-signal input, but the amplitude output signal of circuit can be reduced, cause the power output of circuit to reduce.

[summary of the invention]

Technical problem to be solved by this invention is to overcome existing defective in the above-mentioned prior art, promptly when big audio signal is imported, the problem that output causes harmonic distortion through occurring after the modulation and demodulation cutting the top, and a kind of audio-frequency power amplifier automatic gain control circuit is provided.

The present invention has adopted following technical proposal to solve its technical problem: a kind of audio-frequency power amplifier automatic gain control circuit, comprise a fully differential operational amplifier, this fully differential operational amplifier same, be equipped with divider resistance on the inverting input respectively, and between in-phase input end and the output, all be equipped with feedback resistance between inverting input and the output respectively, a biasing circuit is connected with this fully differential operational amplifier, it is characterized in that: also have an automatic gain control circuit, this automatic gain control circuit input connects the output of fully differential operational amplifier, a reference voltage circuit is connected with this automatic gain control circuit, and the output of this automatic gain control circuit is connected with adjustable resistance on the fully differential operational amplifier input.

The present invention is comparing through in the automatic gain control circuit output signal of fully differential operational amplifier with reference voltage, obtain a digital signal, and this digital signal gone to control variable resistor size before the fully differential operational amplifier input again, thereby realize the automatic adjusting of circuit gain.

[description of drawings]

Fig. 1 is a kind of traditional fully differential operation amplifier circuit structure chart in the prior art;

Fig. 2 is an electrical block diagram of the present invention;

Automatic gain control circuit among Fig. 3 the present invention (AGC) structural representation

Each sequence number is expressed as respectively among the figure:

1-adjustable resistance 1; 2-adjustable resistance 2;

The 3-feedback resistance; The 4-feedback resistance;

5-fully differential operational amplifier; 6-automatic gain control circuit (AGC);

7-audio output 8-reference voltage circuit;

The 9-biasing circuit; 10-operational amplifier (EA);

The 11-clamp circuit; 12-analog to digital conversion circuit (ADC).

[embodiment]

The invention will be further described below in conjunction with embodiment and accompanying drawing.

With reference to Fig. 2, the present invention includes a fully differential operational amplifier 5, be equipped with adjustable resistance 1, adjustable resistance 2 respectively on same, the inverting input of this fully differential operational amplifier 5.Between in-phase input end and output, be equipped with feedback resistance 3, between inverting input and output, be equipped with feedback resistance 4, a biasing circuit 9 is connected with this fully differential operational amplifier 5, the input of an automatic gain control circuit (AGC) 6 connects the audio output 7 of fully differential operational amplifier 5, reference voltage circuit 8 is connected with this automatic gain control circuit 6, and the output of this automatic gain control circuit 6 is connected with adjustable resistance 1,2 on the fully differential operational amplifier input.

With reference to Fig. 3, automatic gain control circuit 6 of the present invention is made of operational amplifier 10, clamp circuit 11 and analog to digital conversion circuit 12.The in-phase input end of this operational amplifier 10 is connected with audio output 7 on the fully differential operational amplifier 5, its inverting input is connected with reference voltage circuit 8, the output of this operational amplifier 10 connects clamp circuit 11 inputs, the output of this clamp circuit 11 connects the input of analog to digital conversion circuit 12, and two outputs on this analog to digital conversion circuit 12 are connected with adjustable resistance 1,2 on 5 two inputs of fully differential operational amplifier respectively.

The input of automatic gain control circuit 6 of the present invention, promptly the in-phase input end of this operational amplifier 10 can be connected with any end in two audio outputs 7 on the fully differential operational amplifier 5 in the circuit.

The particular circuit configurations of the reference voltage circuit 8 described in the present invention, biasing circuit 9, clamp circuit 11, analog to digital conversion circuit 12 all is a circuit of the prior art, is not giving unnecessary details here.

The circuit working principle is as follows among the present invention:

Among the present invention by adjustable resistance 1,2; Fully differential operational amplifier 5; Feedback resistance 3,4 is formed operational amplifier and is amplified loop, and audio input signal is amplified.Audio signal after will amplifying is then come out the audio signal peak detection after this amplification through automatic gain control circuit (AGC) 6, is converted into digital signal again, thereby regulates the resistance of adjustable resistance 1,2, reaches the purpose of the gain that changes circuit.

Audio input signal is from the input port (Vi+ of fully differential operational amplifier 5, Vi-) input, after fully differential arithmetic unit 5 amplifies, output port (Vo+ from this operational amplifier 5, Vo-) output audio signal, this audio signal is connected to the input (IN+) of operational amplifier 10 (EA) in the automatic gain control circuit 6, and compares with the AGC reference voltage.

(1) when the audio output signal peak value less than the AGC reference voltage, be zero through the output voltage after operational amplifier 10 (EA); Signal after this amplification also is zero through the output behind the clamp circuit 11, because the output of clamp circuit 11 does not change, the input analog signal of analog to digital conversion circuit 12 (ADC) does not change yet, so the output of the digital signal of analog to digital conversion circuit 12 does not change, thereby the value of variable resistor 1,2 is constant, and the gain constant of circuit is constant.

(2) when the reference voltage of audio output signal peak value more than or equal to AGC, this audio output signal amplifies audio output signal through operational amplifier 10, again this signal is input to clamp circuit 11, the peak value of clamp circuit 11 these signals of output, and keep constant.This crest voltage changes into the output of string number signal through analog to digital conversion circuit 12 (ADC), this digital output signal is regulated the value of variable resistor 1,2, then change the gain of circuit, crest voltage increases, the resistance of adjustable resistance also increases, circuit gain reduces, and when strengthening input like this, it is constant to export the value that keeps constant.

In sum, of the present inventionly can when small-signal is imported, be maintained fixed gain and amplify audio signal.When importing, big audio signal, guarantees that output audio signal can access the high linearity and low harmonic distortion by reducing the amplifying circuit closed loop gain.

Claims (3)

1. audio-frequency power amplifier automatic gain control circuit, comprise a fully differential operational amplifier, this fully differential operational amplifier same, be equipped with divider resistance on the inverting input respectively, and between in-phase input end and the output, all be equipped with feedback resistance between inverting input and the output respectively, a biasing circuit is connected with this fully differential operational amplifier, it is characterized in that: also have an automatic gain control circuit, this automatic gain control circuit input connects the output of fully differential operational amplifier, a reference voltage circuit is connected with this automatic gain control circuit, and the output of this automatic gain control circuit is connected with adjustable resistance on the fully differential operational amplifier input.
2. audio-frequency power amplifier automatic gain control circuit according to claim 1, it is characterized in that: described automatic gain control circuit is by operational amplifier, clamp circuit and analog to digital conversion circuit constitute, this operational amplifier in-phase input end is connected with audio output on the fully differential operational amplifier, its inverting input is connected with reference voltage circuit, this operational amplifier output terminal connects the clamp circuit input, this clamp circuit output connection mode number conversion circuit input end, two outputs on this analog to digital conversion circuit are connected with adjustable resistance on two inputs of fully differential operational amplifier respectively.
3. according to claim 1 or 2 described audio-frequency power amplifier automatic gain control circuits, it is characterized in that: described automatic gain control circuit input, promptly this operational amplifier in-phase input end of circuit can be connected with any end of two audio outputs on the fully differential operational amplifier.
CN2010101326397A 2010-03-25 2010-03-25 Automatic gain control circuit of audio power amplifier CN102201792A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN2010101326397A CN102201792A (en) 2010-03-25 2010-03-25 Automatic gain control circuit of audio power amplifier

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN2010101326397A CN102201792A (en) 2010-03-25 2010-03-25 Automatic gain control circuit of audio power amplifier

Publications (1)

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CN102201792A true CN102201792A (en) 2011-09-28

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Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102355214A (en) * 2011-10-31 2012-02-15 四川和芯微电子股份有限公司 Adjustable gain audio power amplification circuit
CN102420588A (en) * 2011-12-13 2012-04-18 四川和芯微电子股份有限公司 Signal regulating circuit and method
CN102801396A (en) * 2012-09-12 2012-11-28 电子科技大学 Automatic gain adjustment circuit in audio system
CN102931931A (en) * 2012-11-16 2013-02-13 上海贝岭股份有限公司 Anti-sound break circuit for D-class power amplifier chip
CN102983825A (en) * 2012-11-16 2013-03-20 上海贝岭股份有限公司 Category D amplifier chip
CN103326677A (en) * 2012-03-22 2013-09-25 炬力集成电路设计有限公司 Audio power amplifier and adjusting method thereof
CN103761964A (en) * 2014-01-16 2014-04-30 四川和芯微电子股份有限公司 Automatic voice identification circuit
CN103959644A (en) * 2011-10-10 2014-07-30 阿斯特里姆有限公司 Control system for a power amplifier
CN106656363A (en) * 2016-12-02 2017-05-10 昆明理工大学 Parameter extraction circuit for broadcast supervision receiver and parameter extraction method thereof

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6747515B2 (en) * 2000-04-28 2004-06-08 Stmicroelectronics, Inc. Circuit for automatic regulation of a differential amplifier's gain
CN1770623A (en) * 2004-10-18 2006-05-10 美国芯源系统股份有限公司 Method for high efficiency audio amplifier
CN101373958A (en) * 2007-08-23 2009-02-25 那微微电子科技(上海)有限公司 Automatic gain control circuit and receiver using the same
CN201674469U (en) * 2010-03-25 2010-12-15 上海沙丘微电子有限公司 Audio-frequency power amplifier circuit with automatic gain control circuit

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6747515B2 (en) * 2000-04-28 2004-06-08 Stmicroelectronics, Inc. Circuit for automatic regulation of a differential amplifier's gain
CN1770623A (en) * 2004-10-18 2006-05-10 美国芯源系统股份有限公司 Method for high efficiency audio amplifier
CN101373958A (en) * 2007-08-23 2009-02-25 那微微电子科技(上海)有限公司 Automatic gain control circuit and receiver using the same
CN201674469U (en) * 2010-03-25 2010-12-15 上海沙丘微电子有限公司 Audio-frequency power amplifier circuit with automatic gain control circuit

Cited By (16)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103959644A (en) * 2011-10-10 2014-07-30 阿斯特里姆有限公司 Control system for a power amplifier
CN103959644B (en) * 2011-10-10 2017-10-03 阿斯特里姆有限公司 Power amplifier control system
CN102355214A (en) * 2011-10-31 2012-02-15 四川和芯微电子股份有限公司 Adjustable gain audio power amplification circuit
CN102355214B (en) * 2011-10-31 2014-01-15 四川和芯微电子股份有限公司 Adjustable gain audio power amplification circuit
CN102420588A (en) * 2011-12-13 2012-04-18 四川和芯微电子股份有限公司 Signal regulating circuit and method
CN103326677B (en) * 2012-03-22 2016-05-04 炬芯(珠海)科技有限公司 The control method of audio-frequency power amplifier and audio-frequency power amplifier
CN103326677A (en) * 2012-03-22 2013-09-25 炬力集成电路设计有限公司 Audio power amplifier and adjusting method thereof
CN102801396B (en) * 2012-09-12 2014-10-15 电子科技大学 Automatic gain adjustment circuit in audio system
CN102801396A (en) * 2012-09-12 2012-11-28 电子科技大学 Automatic gain adjustment circuit in audio system
CN102931931B (en) * 2012-11-16 2015-07-08 上海贝岭股份有限公司 Anti-sound break circuit for D-class power amplifier chip
CN102983825B (en) * 2012-11-16 2016-01-13 上海贝岭股份有限公司 A kind of category D amplifier chip
CN102931931A (en) * 2012-11-16 2013-02-13 上海贝岭股份有限公司 Anti-sound break circuit for D-class power amplifier chip
CN102983825A (en) * 2012-11-16 2013-03-20 上海贝岭股份有限公司 Category D amplifier chip
CN103761964A (en) * 2014-01-16 2014-04-30 四川和芯微电子股份有限公司 Automatic voice identification circuit
CN103761964B (en) * 2014-01-16 2016-04-13 四川和芯微电子股份有限公司 Automatic speech recognition circuit
CN106656363A (en) * 2016-12-02 2017-05-10 昆明理工大学 Parameter extraction circuit for broadcast supervision receiver and parameter extraction method thereof

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Application publication date: 20110928

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