CN101499776A - Circuit and method for reducing switching noise of amplifier - Google Patents
Circuit and method for reducing switching noise of amplifier Download PDFInfo
- Publication number
- CN101499776A CN101499776A CN 200810033443 CN200810033443A CN101499776A CN 101499776 A CN101499776 A CN 101499776A CN 200810033443 CN200810033443 CN 200810033443 CN 200810033443 A CN200810033443 A CN 200810033443A CN 101499776 A CN101499776 A CN 101499776A
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- Prior art keywords
- switch
- amplifier
- circuit
- bias voltage
- voltage
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03F—AMPLIFIERS
- H03F3/00—Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements
- H03F3/181—Low frequency amplifiers, e.g. audio preamplifiers
- H03F3/183—Low frequency amplifiers, e.g. audio preamplifiers with semiconductor devices only
- H03F3/187—Low frequency amplifiers, e.g. audio preamplifiers with semiconductor devices only in integrated circuits
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03F—AMPLIFIERS
- H03F1/00—Details of amplifiers with only discharge tubes, only semiconductor devices or only unspecified devices as amplifying elements
- H03F1/30—Modifications of amplifiers to reduce influence of variations of temperature or supply voltage or other physical parameters
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03F—AMPLIFIERS
- H03F3/00—Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements
- H03F3/45—Differential amplifiers
- H03F3/45071—Differential amplifiers with semiconductor devices only
- H03F3/45076—Differential amplifiers with semiconductor devices only characterised by the way of implementation of the active amplifying circuit in the differential amplifier
- H03F3/45475—Differential amplifiers with semiconductor devices only characterised by the way of implementation of the active amplifying circuit in the differential amplifier using IC blocks as the active amplifying circuit
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03F—AMPLIFIERS
- H03F2203/00—Indexing scheme relating to amplifiers with only discharge tubes or only semiconductor devices as amplifying elements covered by H03F3/00
- H03F2203/45—Indexing scheme relating to differential amplifiers
- H03F2203/45138—Two or more differential amplifiers in IC-block form are combined, e.g. measuring amplifiers
Abstract
The invention discloses a circuit used for reducing the noise of an amplifier switch, comprising an amplifier; the circuit is characterized by further comprising a charging/discharging circuit used for providing a bias voltage for the amplifier, a silent switch and a control circuit; and the silence switch provides an overlapping clock signal to the amplifier so as to carry out the shifting operation, wherein, the generated time of the bias voltage is more than an audio range. The circuit adopts an overlapping clock and prevents the amplifier from working at an open ring state during the shifting period, thus reducing the impact caused by the shifting operation, thereby reducing the noise of the switch during the whole switching process.
Description
Technical field
The present invention relates to amplifier region, especially the circuit and the method for the Pop when eliminating switch in the audio-frequency power amplifier field.
Background technology
Fig. 1 shows a kind of differential audio-frequency power amplifier circuit structure commonly used.As shown in Figure 1, resistance R 1, R2, capacitor C b are provided with the dc point of amplifier 11 and amplifier 12; Wherein, Ci is the input capacitance, isolates the input direct current signal; Resistance R m1, Rm2 and amplifier 11 constitute the first order and amplify; Resistance R s1, Rs2 and amplifier 12 constitute the second level and amplify.Amplifier 11 and amplifier 12 outputs are anti-phase, and its differential output is as the output of whole amplifier.During startup, capacitor C b and Ci need be charged to certain value to set up the working point; During shutoff, the electric charge on this electric capacity need be put into zero.
In voice applications, the audio frequency range that people's ear can be heard is 20Hz ~ 20kHz.During switch, if capacitor C b quickly charges to quiescent potential or repid discharge arrives zero, then upward voltage can not be consistent with capacitor C b owing to capacitor C i, and the output of amplifier 11 and 12 also can not be caught up with the variation of input voltage, cause output to have a differential voltage to exist, thereby cause switching noise.Therefore in order to can't hear audio-frequency noise constantly at switch, capacitor C b and capacitor C i need slowly charging when requiring to start, amplifier 11 and 12 common-mode voltage slowly rise, and capacitor C b and capacitor C i slowly discharge when turn-offing, and amplifier 11 and 12 common-mode voltage slowly drop to zero.Keep two output voltage unanimities, do not produce differential voltage output, and the pace of change of single ended voltage is very slow, makes its spectrum component be lower than 20Hz, thereby eliminate switching noise.
Summary of the invention
The objective of the invention is to find out a kind of Method and circuits of step-down amplifier switching noise, switching noise is reduced to the insensitive degree of people's ear.
Above-mentioned in order to realize, a kind of circuit that reduces switching noise of amplifier provided by the invention comprises an amplifier, it is characterized in that described circuit further comprises: a charge-discharge circuit, for described amplifier provides a bias voltage; One silence switch; One control circuit provides the overlapping clock signal to switch by described silence switch to described amplifier; Wherein, the settling time of described bias voltage is greater than an audiorange.
Reasonablely be, described silence switch comprises first and second switch of two series connection, and described overlapping clock signal is controlled described first and second switch respectively, and wherein, when bias voltage was set up, first switch disconnected, the second switch closure; When switching, the conducting simultaneously of described first and second switch.
Reasonable is that described control circuit further comprises a comparator, links to each other with the output of described charge-discharge circuit, overturns when described bias voltage reaches certain value.
Reasonable is that described audiorange comprises 20Hz ~ 20kHz.
Reasonablely be that described overlapping clock signal is controlled described silence switch and reduced voltage difference when switching.
Reasonable is that described audiorange comprises 20Hz ~ 20kHz.
Description of drawings
Below, with reference to accompanying drawing, for those skilled in the art that, from detailed description of the present invention, above-mentioned and other purposes of the present invention, feature and advantage will be apparent.
Fig. 1 is a kind of schematic diagram of audio-frequency power amplifier commonly used;
Fig. 2 is the flow chart of the preferred embodiments of reduction switching noise of the present invention;
Fig. 3 is that bias voltage changes schematic diagram in the switching process of the present invention;
Fig. 4 is the schematic diagram of the preferred embodiments of reduction switching noise of the present invention;
Fig. 5 is the schematic diagram of overlapping clock signal of the present invention.
Embodiment
The invention will be further described below in conjunction with accompanying drawing and example.
Fig. 4 shows the circuit of minimizing switching noise of amplifier of the present invention.This circuit comprises 4 parts: operational amplifier 301, silence switch 302, charge-discharge circuit 303, control circuit 304.Below be introduced one by one:
Charge-discharge circuit 303 comprises four switch S 3, S4, S5, S6, three resistance R 1, R2, R6, capacitor C b, two amplifiers 33,34.Switch S 6 one termination powers, one terminating resistor R1, the other end connecting resistance R2 of resistance R 1 and amplifier 33,34 in-phase input end, the other end ground connection of resistance R 2, the inverting input of amplifier 33 connects an end of its output and switch S 3, another terminated nodes N1 of switch S 3, the inverting input of amplifier 34 connects an end of its output and switch S 4, another terminated nodes N3 of switch S 4 and capacitor C b, one end of resistance R 6, the other end ground connection of capacitor C b, one end of another termination switch S 5 of resistance R 6, the other end ground connection of switch S 5, the inversion signal Nrmfin of the control termination rmfin of switch S 3, the inversion signal Nmute of the control termination mute of switch S 4, the inversion signal NSD1 of the control termination SD1 of switch S 5, the control termination SD1 signal of switch S 6, amplifier 33,34 enable termination SD1.
Control circuit 304 comprise three resistance R 3, R4, R5, two comparators 35,36, delayer 37, with door 38, overlapping clock generator 39.Resistance R 3 one termination powers, the inverting input of other end connecting resistance R4 and comparator 35, the other end connecting resistance R5 of resistance R 4 and the inverting input of comparator 36, the other end ground connection of resistance R 5; The in-phase input end of comparator 35,36 meets N3, the output SD2 of comparator 36, the output rmfin of comparator 35 connects the input of delayer 37, the output mute of delayer 37 connects an input with door 38, another input termination SD1 with door 38, with the input of the output termination overlapping clock generator 39 of door 38, two outputs of overlapping clock generator 39 are respectively ph1 and ph2.
Above-mentioned switch S 1 ~ S6, switch conduction when control signal is " 1 ", switch disconnects when control signal is " 0 ".
Fig. 2 shows the flow chart that the present invention reduces the switching noise of amplifier method, below in conjunction with the circuit of accompanying drawing 4, the flow process that reduces noise is described in detail.
Step 1: in the charge-discharge circuit 303, when enabling signal SD1 becomes " 1 " by " 0 ", entire circuit starts, and enters charging zone shown in Figure 3.At this moment, buffer 33 and 34 is given capacitor C i and Cb charging respectively, and node N3 voltage slowly rises.This moment rmfin=mute=" 0 ", Nrmfin=Nmute=" 1 ", ph1=" 0 ", ph2=" 1 ", NSD1=" 0 ", switch S 1 and S5 disconnect, and switch S 2, S3 and S4 closure.The voltage vo1 of inverting input and in-phase input end and vo2 follow node N3 voltage and slowly rise, vo=vo1-vo2=0V, and signal source Vs is to vo1 and the not influence of vo2 voltage.
Step 2: when node N3 voltage rises to certain value, comparator 35 upsets, rmfin becomes " 1 " from " 0 ", Nrmfin=0, switch S 3 disconnects, and the voltage that discharges and recharges by capacitor C b of capacitor C i decides, and this moment, system was in quiet district.In quiet district, control discharging and recharging of Ci by the voltage of capacitor C b, can improve the consistency of capacitor C b and capacitor C i charging, the inconsistent impacts that cause because two electric capacity charge when reducing switch.
Step 3: after 37 couples of rmfin of delayer carried out one section time-delay, mute also became " 1 " from " 0 ", and Nmute becomes " 0 ", and switch S 4 also disconnects.Because the effect of overlapping clock generator 39, as shown in Figure 5, ph1 becomes " 1 " earlier, ph2 becomes " 0 " more then, and the S1 cut-off switch S2 again that promptly closes a switch earlier does following benefit like this: because the influence of signal source Vs, may there be very big-difference in node N1 and N2 voltage, if close S1 after S2 disconnects, then the N2 point voltage can sport the N1 point voltage, and this can produce very big impact in the output of amplifier 31; And the S1 that under the situation that S2 closes, closes a switch, then the voltage of node N1 can bleed off by switch S 1 and S2 path, makes node N1 and N2 voltage be tending towards equal, and this moment, stopcock S2 just can reduce the impact of node N1 to N2 again.
Step 4: by above-mentioned three steps, system has finished the start-up course that does not have noise.When turn-offing, SD1 becomes " 0 " by " 1 ", and NSD1 becomes " 1 ", and switch S 5 is closed, capacitor C b slowly discharge by resistance R 6, and comparator 36 is output as height at this moment, i.e. SD2=" 1 ", ph1=" 0 ", ph2=" 1 ", switch S 1 disconnects switch S 2 closures.The voltage that amplifier 31 and 32 output voltage vo1, vo2 follow node N3 reduces, vo=vo1-vo2=0V, and this moment, signal source Vs was to not influence of output voltage vo1, vo2.
Step 5: when the voltage of capacitor C b is put into when enough low, comparator 36 upsets, SD2 becomes level "0", closes whole system.
Should be understood that when starting, the invention reside in the slow foundation that utilizes bias voltage, the time that makes foundation is greater than audiorange, thereby the working point being set up do not produce in the process can audible noise.In the process that this voltage is set up, utilize silence switch S1 disconnection, S2 closure, and after bias voltage foundation is finished, in switch S 1, S2 stateful switchover process, adopted the overlapping clock, make silence switch in handoff procedure, have switch S 1, the S2 conducting simultaneously of moment, the voltage difference of node N1 and N2 when reducing switching; During shutoff, utilize the slow discharge of bias voltage, and the overlapping clock of silence switch when switching, the voltage difference of node N2 and vo1 when reducing switching, just as the example explanation, the implementation of mode that discharges and recharges and determination methods, silence switch control clock signal, the connected mode of operational amplifier can not limit the present invention to above-mentioned example.
The present invention contrasts prior art, and by following beneficial effect: as shown in Figure 2, the present invention is divided into three phases with start-up course, is respectively charging zone, quiet district and service area, does not accept the audio signal input at charging zone and quiet district.Wait for that amplifier is stabilized in a normal working point lentamente, accept audio signal then, so just avoided that output signal is arranged when instability.And turn off process is divided into two stages, is respectively region of discharge and turn-offs the district, and equal received audio signal not in these two zones waits for that the working point of amplifier slowly reduces to zero.So just can in switching process, carry out better controlled, avoid the working point also not have amplifying signal stable the time audio signal; Adopt the overlapping clock when between shutdown signal and amplifying signal, switching, prevent that amplifier is operated in open loop situations between transfer period, thereby reduce to switch the impact that causes, thereby reduce the switching noise of whole switching process.
Above-mentioned example provides to those of ordinary skills and realizes or use of the present invention; those of ordinary skill in the art can be under the situation that does not break away from invention thought of the present invention; above-mentioned example is made various modifications or variation; thereby protection scope of the present invention do not limit by above-mentioned example, and should be the maximum magnitude that meets the inventive features that claims mention.
Claims (6)
1, a kind of circuit that reduces switching noise of amplifier comprises an amplifier, it is characterized in that, described circuit further comprises:
One charge-discharge circuit is for described amplifier provides a bias voltage;
One silence switch;
One control circuit provides the overlapping clock signal to switch by described silence switch to described amplifier;
Wherein, the settling time of described bias voltage is greater than an audiorange.
2, circuit according to claim 1 is characterized in that,
Described silence switch comprises first and second switch of two series connection, and described overlapping clock signal is controlled described first and second switch respectively, wherein,
When bias voltage was set up, first switch disconnected, the second switch closure;
When switching, the conducting simultaneously of described first and second switch.
3, circuit according to claim 2 is characterized in that,
Described control circuit further comprises a comparator, links to each other with the output of described charge-discharge circuit, overturns when described bias voltage reaches certain value.
4, circuit according to claim 3 is characterized in that,
Described audiorange comprises 20Hz ~ 20kHz.
5, a kind of method of utilizing the described circuit of claim 1 is characterized in that,
Described overlapping clock signal is controlled described silence switch and is reduced voltage difference when switching.
6, method according to claim 5 is characterized in that,
Described audiorange comprises 20Hz ~ 20kHz.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 200810033443 CN101499776A (en) | 2008-02-02 | 2008-02-02 | Circuit and method for reducing switching noise of amplifier |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 200810033443 CN101499776A (en) | 2008-02-02 | 2008-02-02 | Circuit and method for reducing switching noise of amplifier |
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| Publication Number | Publication Date |
|---|---|
| CN101499776A true CN101499776A (en) | 2009-08-05 |
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| CN 200810033443 Pending CN101499776A (en) | 2008-02-02 | 2008-02-02 | Circuit and method for reducing switching noise of amplifier |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103327268A (en) * | 2012-03-21 | 2013-09-25 | 佳能株式会社 | Image pickup apparatus |
| WO2018045770A1 (en) * | 2016-09-12 | 2018-03-15 | 京东方科技集团股份有限公司 | Control circuit, control method and electronic device |
| CN116346107A (en) * | 2023-05-31 | 2023-06-27 | 广东工业大学 | HBT-based radio frequency switch |
-
2008
- 2008-02-02 CN CN 200810033443 patent/CN101499776A/en active Pending
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103327268A (en) * | 2012-03-21 | 2013-09-25 | 佳能株式会社 | Image pickup apparatus |
| CN103327268B (en) * | 2012-03-21 | 2016-12-28 | 佳能株式会社 | Image pick-up device |
| WO2018045770A1 (en) * | 2016-09-12 | 2018-03-15 | 京东方科技集团股份有限公司 | Control circuit, control method and electronic device |
| US10298180B2 (en) | 2016-09-12 | 2019-05-21 | Boe Technology Group Co., Ltd. | Control circuit, control method, and electronic device |
| CN116346107A (en) * | 2023-05-31 | 2023-06-27 | 广东工业大学 | HBT-based radio frequency switch |
| CN116346107B (en) * | 2023-05-31 | 2023-08-11 | 广东工业大学 | HBT-based radio frequency switch |
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Application publication date: 20090805 |