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ID:1508783
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时间:2017-11-12
《三,网络元件与偏置电路对噪声的影响》由会员上传分享,免费在线阅读,更多相关内容在教育资源-天天文库。
1、三、网络元件与偏置电路对噪声的影响Theinfluencesofnetcomponents&biascircuitsonnoise1、串、并联网络对噪声的影响Theinfluenceofseries、parallelnetworkonnoisea.并联耦合网络b.串联耦合网络parallelcouplingnetworkseriescouplingnetwork图中::源阻抗,;Sourceimpedance:并联网络阻抗,;Parallelnetworkimpedance:串联网络阻抗,;Seriesnetworkimpedance:源电阻热噪声电压,;The
2、rmalnoisevoltageofsourceresistance:并联阻抗实部噪声电流;Therealpartofthenoisecurrentofparallelimpedance.:串联阻抗实部噪声电压;Therealpartofthenoisevoltageofseriesimpedance.、:放大器噪声模型;Noisemodelofaamplifier:放大器电压增益;Amplifier’svoltagegain:输出噪声电压。Outputnoisevoltage(1)并联网络Parallelnetwork各噪声源在输出端开路时的分量为Thecom
3、ponentsofeachnoisesourceonoutputend(opencircuit)are总输出噪声均方值为Thetotaloutputnoisemeansquarevalueis(3.1.75)网络电压传输增益为Thenetworkvoltagetransmissiongainis(3.1.76)等效输入噪声为Theequivalentinputnoiseis(3.1.77)(3.1.78)表明Showingthat若欲减小并联网络对噪声的影响,需使并联网络阻抗的直流电阻尽可能增大,同时使上的噪声电流尽可能减小。Toreducetheinfluen
4、ceofparallelnetworkonnoise,theDCresistanceoftheparallelnetworkimpedanceshouldbeincreasedaslargeaspossible,andthenoisecurrentonthedecreasedassmallaspossible.中包含两个部分Theincludestwoparts:<1>热噪声电压,它与成反比;Thethermalnoisevoltage,whichisinverselyproportionaltothe.<2>流过的低频噪声电流,它与流过的直流电平成正比。The
5、low-frequencynoisecurrentflowingthroughthe,whichisdirectlyproportionaltotheDClevelofthe.故欲减小,还需尽量减小上的直流压降。Therefore,theDCvoltagedroponthehastobereducedtoreducethe.(2)串联网络Seriesnetwork先求出各噪声源在输出端开路时输出的分量分别为:Theoutputcomponentsofeachnoisesource(opencircuit)are得总输出噪声电压均方值为Thenthetotalou
6、tputnoisevoltagemeansquarevalueis电压传输增益为Thevoltagetransmissiongainis等效输入噪声为Theequivalentinputnoiseis(3.1.79)表明Showingthat:欲减小串联网络对噪声的影响,应使尽可能小,并尽量减小上的噪声电压,上的直流压降也应尽量减小。Allthe,thenoisevoltageontheandtheDCvoltagedropontheshouldbedecreasedassmallaspossibletoreducetheinfluenceoftheseries
7、networkonthesystemnoise.(3)并串联网络(导出过程留在习题课中解决)ThenoiseanalysisofParallel-SeriesNetworks(Thederivationwillbesolvedinexercises-lesson)(3.1.79)(4)串并联网络ThenoiseanalysisofSeries-ParallelNetworks(3.1.80)上二式表明:若欲减小网络对噪声的影响,对并联网络,要尽可能提高并联阻抗的数值;对串联网络,要尽可能减小串联电阻抗的数值。同时,两者都应尽可能减小网络阻抗上的压降,以减小低频噪
8、声。Toreduceth
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