Empeleni, ibhodi yesifunda ephrintiwe (I-PCB) zenziwe ngezinto ezihamba ngogesi, okusho ukuthi impedance yazo kufanele ihlale ingaguquguquki. Manje kungani i-PCB ingenisa ukungahambisani nolunye uphawu kusiginali? Impendulo ukuthi ukwakheka kwe-PCB “kungokwendawo okungeyona eyomugqa” maqondana nalapho kugobhoza khona manje.

Ukuthi i-amplifier ithola i-current kusuka komunye umthombo noma komunye kuya nge-polarity yesiginali esheshayo kulayini. Ukugeleza kwamanje kusuka ekunikezelweni kwamandla, ngokusebenzisa i-bypass capacitor, ngokusebenzisa i-amplifier ekulayisheni. 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. Endizeni yomhlaba, kuvame ukuba nezindlela ezingaphezu kweyodwa ze-impedance ephansi lapho ingxenye enkulu yokugeleza kwamanje komhlaba: indlela eyodwa ixhunywe ngqo ne-bypass capacitor; Enye ijabulisa ukumelana nokufaka kuze kufinyelelwe i-bypass capacitor. Umdwebo 1 ukhombisa lezi zindlela ezimbili. I-backflow yamanje yiyona edala inkinga.

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Lapho ama-capacitor we-bypass abekwa ezindaweni ezahlukahlukene ku-PCB, amandla aphansi komhlaba ageleza ngezindlela ezahlukahlukene eziya kuma-bypass capacitors, okuyincazelo ye- “nonlinearity spatial”. 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. Uma okunye ukuphakama kwamanje womhlaba kungaphazanyiswa, i-voltage yesiginali yokufaka iyashintsha ngendlela engeyona eyomugqa. Lapho ingxenye eyodwa ye-polarity ishintshwa kepha enye i-polarity ingekho, ukuhlanekezela kwenzeka futhi kubonakale njengokuhlanekezelwa kwesibili kwe-harmonic kwesiginali yokukhipha. Umdwebo 2 ukhombisa lo mphumela wokuhlanekezela ngesimo sehaba.

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Lapho kuphela into eyodwa ye-polar ye-sine wave ephazamisekile, ifomu le-wave elivelayo aliseyona i-sine wave. Ukulingisa i-amplifier ekahle enokulayishwa okungu-100-and nokuhlanganisa umthwalo wamanje ngokusebenzisa isiphikisi esingu-1-into kumandla omoya womhlaba ku-polarity eyodwa kuphela yesiginali, okuholela emfanekisweni wesi-3. Fourier transform shows that the distortion waveform is almost all the second harmonics at -68 DBC. Ezimweni eziphakeme kakhulu, leli zinga lokuhlanganisa lenziwa kalula kwi-PCB, engabhubhisa izici ezinhle kakhulu zokulwa nokuhlanekezelwa kwesikhulisi ngaphandle kokusebenzisa imiphumela eminingi ekhethekile engahambelani nomugqa ye-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

Inkinga yama-chip multi-amplifier chips (ama-amplifiers amabili, amathathu, noma amane) ihlanganiswe nokungakwazi ukugcina ukuxhumana komhlaba we-bypass capacitor kukude kukho konke okokufaka. Lokhu kuyiqiniso ikakhulukazi kuma-amplifiers amane. Ama-chips ama-Quad-amplifier anama-terminals wokufaka ohlangothini ngalunye, ngakho-ke ayikho indawo yamasekethe okudlula anciphisa ukuphazamiseka esiteshini sokufaka.

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Umdwebo 5 ukhombisa indlela elula yokuhlelwa kwama-amplifier amane. Iningi lamadivayisi lixhuma ngqo kuphini le-quad amplifier. Amandla aphansi womthamo owodwa wamandla angaphazamisa amandla wokufaka womhlaba namandla wamanje womunye amandla wesiteshi, okuholele ekuhlanekezelweni. Isibonelo, i- (+ Vs) eyedlula i-capacitor esiteshini 1 se-quad amplifier ingabekwa ngqo eduze kokufakwayo; I (-Vs) yokudlula capacitor ingafakwa kolunye uhlangothi lwephakheji. Okwamanje umhlaba (+ Vs) ungaphazamisa isiteshi 1, kuyilapho i-(-vs) yamanje ingasebenzi.

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Ukugwema le nkinga, vumela umhlabathi wamanje uphazamise okokufaka, kepha vumela ukugeleza kwamanje kwe-PCB ngendlela yolayini. Ukufeza lokhu, i-bypass capacitor ingahlelwa ku-PCB ngendlela yokuthi (+ Vs) kanye (- Vs) nemisinga yomhlabathi igeleze ngendlela efanayo. Uma isignali yokufaka iphazanyiswa ngokulinganayo yimisinga emihle nengalungile, ukuhlanekezelwa ngeke kwenzeke. Ngakho-ke, qondanisa ama-capacitors amabili adlula eduze komunye nomunye ukuze abelane ngephuzu lomhlabathi. Ngoba izingxenye ezimbili ze-polar zamanje zomhlaba zivela endaweni efanayo (isivalo sokuxhuma okukhiphayo noma umhlaba olayishayo) futhi zombili zigeleza zibuyela endaweni efanayo (ukuxhumana komhlaba okuvamile kwe-bypass capacitor), okwamanje okuhle / okungalungile kudlula indlela efanayo. Uma ukumelana kokufaka kwesiteshi kuphazanyiswa yi- (+ Vs) yamanje, (- Vs) yamanje kunomthelela ofanayo kuso. 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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Ukuqinisekisa okushiwo ngenhla, kusetshenziswe izakhiwo ezimbili ezihlukile ze-PCB: ukwakheka okulula (Umdwebo 5) nokuhlelwa kokuhlanekezela okuphansi (Umdwebo 6). Ukuhlanekezelwa okwenziwe yi-FHP3450 quad-functional amplifier esebenzisa i-fairchild semiconductor kubonisiwe kuthebula 1. Ububanzi bomkhawulo ojwayelekile we-FHP3450 ngu-210MHz, i-slope ingu-1100V / us, i-input bias current yi-100nA, futhi isiteshi esisebenzayo esiteshini ngasinye siyi-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. Ngokusobala, isiteshi se-amplifier esinikiwe asiphazamisi okokufaka kwaso kuphela, kepha nokufakwa kwezinye iziteshi. The earth current flows through all the different channel inputs and produces different effects, but is influenced by each output, which is measurable.

Ithebula 2 likhombisa ama-harmoniki alinganiswa kwezinye iziteshi ezingasetshenziswanga lapho kuqhutshwa isiteshi esisodwa kuphela. Isiteshi esingabanjwanga sikhombisa isignali encane (i-crosstalk) kumvamisa oyisisekelo, kepha futhi sikhiqiza ukuhlanekezela okulethwe ngqo ngumswakamo womhlaba ngokungabi bikho kwesiginali ebalulekile. Ukuhlelwa kokuhlanekezelwa okuphansi kuMdwebo 6 kukhombisa ukuthi izici zesibili ze-harmonic ne-harmonic distension (THD) zithuthukiswe kakhulu ngenxa yokususwa komphumela wamanje womhlaba.

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Lesi sifinyezo sendatshana

Kalula nje, kwi-PCB, ukugeleza emuva okugeleza kudlula kuma-capacitors ahlukile (okwehlukile kwamandla kagesi) namandla kagesi uqobo, alingana nokusebenza kwawo. Isiginali yesignali ephezulu kakhulu ibuyela emuva kwi-capacitor encane yokudlula. Imisinga yemvamisa ephansi, njengaleyo yamasignali alalelwayo, ingageleza ngokuyinhloko ngokudlula kwama-capacitors amakhulu. Noma imvamisa ephansi ingahle “inganaki” amandla we-bypass agcwele futhi igeleze ibuyele ngqo kumthofu wamandla. Uhlelo lokusebenza oluthile luzonquma ukuthi iyiphi indlela yamanje ebaluleke kakhulu. 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.

Umthetho wegolide wokuhlelwa kwe-HF PCB ukugcina i-HF bypass capacitor iseduze kwephini lamandla ahlanganisiwe ngangokunokwenzeka, kepha ukuqhathaniswa kwe-Figure 5 ne-Figure 6 kukhombisa ukuthi ukuguqula lo mthetho ukuthuthukisa izici zokuhlanekezela akuwenzi mehluko omkhulu. Izici ezithuthukisiwe zokuhlanekezela zavela enkingeni yokwengeza cishe ama-intshi ayi-0.15 we-high-frequency bypass capacitor wiring, kepha lokhu kube nomthelela omncane ekusebenzeni kokuphendula kwe-AC kwe-FHP3450. Ukuhlelwa kwe-PCB kubalulekile ukukhulisa ukusebenza kwesikhulisi sekhwalithi ephezulu, futhi izingqinamba ezixoxwe lapha azigcini kuma-hf amplifiers. Amasiginali wemvamisa engezansi njengomsindo unezidingo eziqinile zokuhlanekezela. Umphumela wamanje womhlaba mncane kumafrikhwensi aphansi, kepha kungenzeka kube yinkinga ebalulekile uma inkomba yokuhlanekezela edingekayo ithuthukiswa ngokufanele.