Ae o le mea moni, lolomi laupapa matagaluega (PCB) e faia i eletise laina mea, ie latou impedance tatau ona tumau. Ma aisea la e faʻaalia ai e le PCB le le felagolagomaʻi i se faʻailo? O le tali o le faʻavae PCB o le “spatially non-linear” e faʻatatau i le mea o loʻo tafe ai nei.

Pe o le amplifier mauaina nei mai se tasi faʻavae poʻo se isi faʻamoemoeina i le vave polarity o le faʻailoga i luga o le avega. Tafe o loʻo i ai nei mai le sapalai o le eletise, e ala i le bypass capacitor, ala i le amplifier i totonu o le uta. The current then travels from the load ground terminal (or shielding of the PCB output connector) back to the ground plane, through the bypass capacitor, and back to the source that originally supplied the current.

The concept of minimum path of current through impedance is incorrect. The amount of current in all different impedance paths is proportional to its conductivity. I totonu o le eleele vaʻalele, e masani ona sili atu ma le tasi le maualalo-faʻafuaseʻi auala e ala ai ona tele se vaega o le eleele taimi nei tafe: tasi le ala e fesoʻotaʻi tuʻusaʻo i le bypass capacitor; O leisi e faʻafiafiaina le sao o mea e faʻaulu ai seʻia oʻo ina taunuʻu le mea e fai ai le auala. Ata 1 faʻamatalaina nei ala e lua. O le alualu i luma o le taimi nei o le mea moni mafua ai le faʻafitauli.

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A o le bypass capacitors ua tuʻu i tulaga eseese i luga ole PCB, o le eleele nei e tafe i auala eseese i le bypass by capacitors, o le uiga lea o le “spatial nonlinearity”. If a significant portion of a polar component of the ground current flows through the ground of the input circuit, only that polar component of the signal is disturbed. Afai o le isi polarity o le eleele taimi nei e le faʻalavelaveina, o le sao signal voltage suia i se nonlinear faiga. A o le tasi polarity vaega ua suia ae o le isi polarity e leai, faʻaletonu tupu ma ua faʻaalia o le lona lua ogatasi feeseeseaiga o le galuega faʻailo. Ata 2 o loʻo faʻaalia ai lenei faʻapiʻopiʻo aafiaga i le soona faʻateleina foliga.

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A naʻo le tasi vaega polar o le sine galu e faʻalavelave, o le faʻaiuga galu ua le toe avea ma galu sine. Faʻafoliga o se mea lelei e faʻateleina ma se uta 100-ω ma faʻapipiʻi le avega i le taimi nei e ala i le 1-ω resistor i totonu o le eleele voltage i luga o le tasi polarity o le faʻailo, iʻuga o le numera 3. Fourier transform shows that the distortion waveform is almost all the second harmonics at -68 DBC. I le maualuga o alaleo, o lenei tulaga o faʻatasiga e faigofie ona faʻatupuina i luga o le PCB, lea e mafai ona faʻaleagaina ai le sili atu anti-faʻasese uiga o se mea faʻatele e aunoa ma le faʻaaogaina o le tele o faʻapitoa leai laina laina aʻafiaga o se PCB. When the output of a single operational amplifier is distorted due to the ground current path, the ground current flow can be adjusted by rearranging the bypass loop and maintaining distance from the input device, as shown in Figure 4.

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Multiamplifier chip

O le faʻafitauli o chips e tele-amplifier (lua, tolu, poʻo le fa amplifiers) o loʻo tuʻufaʻatasia e le le mafai ona taofia le faʻaogaina o le auala o le capacitor bypass mamao mai le sao atoa. E moni lenei mea mo le fa amalama. Quad-amplifier chips o loʻo iai ni faʻaulufaleina i itu taʻitasi, o lona uiga e leai se avanoa mo taʻamilosaga faʻasolosolo e faʻaititia ai le faʻalavelave i le auala sao.

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Ata 5 o loʻo faʻaalia ai se auala faigofie i le fa-amplifier layout. Tele o masini fesoʻotaʻi saʻo i le quad amplifier pin. O le eleele i le taimi nei o le tasi paoa sapalai mafai ona faʻalavelaveina le sao eleele voltage ma eleele taimi nei o le isi auala eletise sapalai, ma mafua ai le faʻaletonu. Mo se faʻataʻitaʻiga, o le (+ Vs) aloese capacitor i luga o le auala 1 o le quad amplifier e mafai ona tuʻu saʻo faʻatalata atu i lona sao; O le (-Vs) bypass capacitor mafai ona tuʻu i le isi itu o le afifi. O le (+ Vs) eleele i le taimi nei mafai ona faʻalavelaveina auala 1, ae o le (-vs) eleele taimi nei atonu e le.

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Ina ia aloese mai lenei faʻafitauli, ia o le eleele taimi nei faʻalavelaveina le sao, ae ia avea le PCB nei tafe i totonu o se spatially laina masani. Ina ia ausia lenei mea, o le bypass capacitor mafai ona faʻatulagaina i luga o le PCB i se auala o le (+ Vs) ma le (- Vs) eleele āu e tafe i totonu o le ala lava e tasi. A faʻapea o le faʻaulufaleina o faʻailo e tutusa faʻasoesa e ala lelei ma le lelei o tafega, e le tupu se faʻaletonu. O le mea lea, faʻatulaga ia lua bypass capacitors i autafa o le tasi ma le isi ina ia latou fefaʻasoaaʻi se eleele manatu. Talu ai o vaega e lua o le lalolagi o loʻo i ai nei e sau mai le mea e tasi (o le gaosiga o fesoʻotaʻiga puipuia poʻo le avega eleele) ma uma tafe toe foi i le tutusa itu (o le masani eleele fesoʻotaʻiga o le bypass capacitor), o le lelei / le lelei o loʻo i ai nei e tafe atu i totonu o le ala lava e tasi. Afai o le input input o se auala ua faʻalavelaveina e (+ Vs) nei, (- Vs) o loʻo i ai nei le tutusa aafiaga i ai. Because the resulting disturbance is the same regardless of the polarity, there is no distortion, but a small change in the gain of the channel will occur, as shown in Figure 6.

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Ina ia faʻamaonia le mea ua taua i luga, e lua faʻasologa PCB eseʻese na faʻaaogaina: o se faʻavasega faigofie (Ata 5) ma se faʻataʻatiaga maualalo (Faʻatusa 6). O le faʻaletonu na gaosia e le FHP3450 quad-operating amplifier e faʻaaogaina ai le fairchild semiconductor o loʻo faʻaalia i le laulau 1. O le bandwidth masani a le FHP3450 o 210MHz, o le slope o 1100V / us, o le input bias o loʻo i ai nei o 100nA, ma o loʻo faʻaaogaina nei i le auala e 3.6 mA As can be seen from Table 1, the more distorted the channel, the better the improvement, so that the four channels are nearly equal in performance.

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Without an ideal quad amplifier on a PCB, measuring the effects of a single amplifier channel can be difficult. E manino lava, o se auala e faʻateleina ai auala e faʻalavelave ai e le gata i lona ia lava sao, ae o le sao o isi auala faʻapena foi. The earth current flows through all the different channel inputs and produces different effects, but is influenced by each output, which is measurable.

Lisi 2 faʻaalia ai le fealofani fuaina i luga o isi auala undriven pe a na o le tasi auala e tulia. O le undriven auala faʻaalia se laʻititi faʻailo (crosstalk) i le faʻavae faʻavae taimi, ae faʻapenaina foi distortion faʻatonutonu tuusaʻo e le eleele nei i le leai o se taua faʻailoga taua. O le maualalo-faʻavasegaina faʻatulagaina i le Ata 6 o loʻo faʻaalia ai o le lona lua ogatasi ma le aofaʻi o le feʻaveaʻiina o feʻau (THD) ua faʻaleleia atili ona o le latalata-faʻateʻaina o le eleele taimi nei aʻafiaga.

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Lenei tusitusiga aotelega

Na ona tuu, luga o le PCB, o le backflow nei tafe tafe ala eseese capacitors bypass (mo eseese sapalai o le eletise) ma le paoa sapalai lava ia, lea e tutusa ma lona conductivity. O le taimi nei-maualuga faailo taimi nei tafe toe foi i le laiti bypass capacitor. Galu maualalo-taimi, e pei o na o leo leo, ono tafe muamua lava i sili atu bypass capacitors. E oʻo lava i le paʻu maualalo o taimi e mafai ona “le amanaʻiaina” le atoa bypass capacitance ma tafe saʻo i tua i le paʻu taʻimua. O le faʻapitoa talosaga o le a fuafua ai le taimi nei ala e sili ona taua. Fortunately, it is easy to protect the entire ground current path by using a common ground point and a ground bypass capacitor on the output side.

O le tulafono faʻaauro mo le HF PCB faʻataʻitaʻiga o le tausia o le HF bypass capacitor latalata i le afifi mana pine mafai, ae o se faʻatusatusaga o le Ata 5 ma le Ata 6 o loʻo faʻaalia ai o le fesuiaʻia o lenei tulafono e faʻaleleia atili ai uiga faʻaletonu e le tele se eseesega. O le faʻaleleia atili o uiga faʻaletonu na oʻo mai i le totogi o le faʻaopopoina e tusa ma le 0.15 inisi o le maualuga o le televave o le faʻaaogaina o uaea uila, ae o lenei mea e leai se aʻafiaga i le tali atu a le AC o le FHP3450. E taua le faʻataʻatiaga ole PCB e faʻateleina ai le faʻatinoina ole mea e faʻaaoga ai le leo maualuga, ma o mataupu e talanoaina iinei e le gata i le hf amplifiers. Maualalo taimi faʻailo pei o leo e sili atu ona faigata faʻapiʻopiʻo manaʻoga. O le eleele i le taimi nei aafiaga e laʻititi ifo i lalo maualalo, ae ono avea pea ma se faʻafitauli taua pe a fai o le manaʻoga faʻapitoa faʻailoga e faʻaleleia atili.