Pamenepo, bolodi losindikizidwa (PCB) amapangidwa ndi zida zamagetsi zamagetsi, mwachitsanzo, ma impedance awo amayenera kukhala osasintha. Nanga n’chifukwa chiyani PCB imayambitsa kusagwirizana mu chizindikiro? Yankho lake ndikuti masanjidwe a PCB ndi “okonda malo opanda mzere” poyerekeza ndi komwe kukuyenda pano.

Kaya mkuzamawu amalandila pakadali pano kuchokera kwina kapena kwina kumadalira polarity yomwe ikupezeka pakatunduyo. Zomwe zikuyenda kuchokera pamagulitsidwe amagetsi, kudzera pa capacitor yolambalalitsira, kudzera pama amplifier kulowa. 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. Ndege yapansi, nthawi zambiri pamakhala njira zopitilira impedance zocheperako pomwe gawo lalikulu lamtunda likuyenda: njira imodzi yolumikizidwa mwachindunji kulambalala kwa capacitor; China chimakondweretsa cholumikizira mpaka kulowetsa capacitor kukafika. Chithunzi 1 chikuwonetsa njira ziwirizi. Kutsika kwakumbuyo ndi komwe kumayambitsa vuto.

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Ma capacitors odutsa akaikidwa m’malo osiyanasiyana pa PCB, nthaka yapansi imadutsa njira zosiyanasiyana kupita kuzolowera, zomwe ndiye tanthauzo la “malo osagwirizana”. 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. Ngati mawonekedwe ena apansi pano sanasokonezeke, mayendedwe amtundu wamagetsi amasintha m’njira yopanda mzere. Gawo limodzi lokhala polarity likasinthidwa koma polarity inayo silisintha, kupotoza kumachitika ndipo kumawonetsedwa ngati kupotoza kwachiwiri kwa harmonic kwa chizindikirocho. Chithunzi 2 chikuwonetsa kusokonekera uku mu mawonekedwe okokomeza.

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Pomwe gawo limodzi lokha la polar pamafunde a sine lasokonezeka, mawonekedwe amtsinjewo sakhalanso mafunde a sine. Kuyimitsa chopukusira choyenera chokhala ndi 100-ω katundu ndikulumikiza katundu wapano kudzera mu 1-ω resistor mu voliyumu yapansi palowala limodzi la chizindikirocho, zotsatira zake chithunzi 3. Fourier transform shows that the distortion waveform is almost all the second harmonics at -68 DBC. Pamwamba pafupipafupi, mulingo wolumikizawu umapangidwa mosavuta pa PCB, yomwe imatha kuwononga zabwino zotsutsana ndi zosokoneza zama amplifier osagwiritsa ntchito zovuta zapadera za 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

Vuto la tchipisi tambirimbiri (ma amplifiers awiri, atatu, kapena anayi) limaphatikizidwa ndi kulephera kusunga kulumikizana kwapansi kwa capacitor capacitor kutali ndi kulowetsa konse. Izi ndizowona makamaka kwa ma amplifiers anayi. Ma tchipisi a Quad-amplifier ali ndi malo olowera mbali iliyonse, motero palibe malo opitilira ma circuits omwe amachepetsa kusokonekera kwa njira yolowera.

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Chithunzi 5 chikuwonetsa njira yosavuta pamakonzedwe anayi azokweza. Zipangizo zambiri zimalumikizana ndi pini ya quad amplifier. Mphamvu yapano yamagetsi imodzi imatha kusokoneza ma voliyumu olowetsa pansi ndi mphamvu zapano zamagetsi zamagetsi, zomwe zimapangitsa kusokonekera. Mwachitsanzo, (+ Vs) yodutsa capacitor pa njira 1 ya quad amplifier imatha kuyikidwa moyandikana ndi zomwe imalemba; (-Vs) yodutsa capacitor imatha kuyikidwa mbali inayo ya phukusi. Zomwe zilipo (+ Vs) pakali pano zimatha kusokoneza njira 1, pomwe ma (-vs) pakadali pano sangatero.

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Pofuna kupewa vutoli, lolani nthaka pakali pano isokoneze zolowetsazo, koma lolani kuti PCB ikuyenda mosadukiza. Kuti mukwaniritse izi, podutsa capacitor amatha kukonza pa PCB m’njira yoti (+ Vs) ndi (- Vs) mafunde apansi aziyenda m’njira yomweyo. Ngati chizindikiro cholowetsacho chimasokonezedwanso ndimayendedwe abwino ndi oyipa, kupotoza sikungachitike. Chifukwa chake, ikani zigawo ziwiri zapambuyo pambali kuti zigawane pansi. Chifukwa zigawo ziwiri za polar zapadziko lapansi pano zimachokera kumalo omwewo (zotulutsa zolumikizira zotetezera kapena nthaka yolemetsa) ndipo zonse zimabwerera kumalo omwewo (kulumikizana kofananira kwa capacitor capacitor), zabwino / zoyipa pakadali pano zimadutsa njira yomweyo. Ngati kulowerera kwa njira kumasokonezedwa ndi (+ Vs) zamakono, (- Vs) zamakono zimakhudzanso zomwezo. 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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Kuti mutsimikizire zomwe zanenedwa pamwambapa, masanjidwe awiri osiyana a PCB adagwiritsidwa ntchito: mawonekedwe osavuta (Chithunzi 5) ndi mawonekedwe osokoneza pang’ono (Chithunzi 6). Kupotoza kopangidwa ndi FHP3450 quad-operating amplifier pogwiritsa ntchito fairchild semiconductor kukuwonetsedwa patebulo 1. Mawonekedwe oyenda a FHP3450 ndi 210MHz, kutsetsereka kwake ndi 1100V / ife, zomwe zikulowererapo pano ndi 100nA, ndipo magwiridwe antchito pachiteshi chilichonse ndi 3.6 MAU. 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. Zachidziwikire, njira yolimbikitsira samasokoneza zolowetsa zake zokha, komanso zolowetsa njira zina. The earth current flows through all the different channel inputs and produces different effects, but is influenced by each output, which is measurable.

Tebulo 2 likuwonetsa ma harmoniki omwe amayeza njira zina zosayendetsa pomwe njira imodzi yokha imayendetsedwa. Msewu wosatulutsidwa umawonetsa chizindikiro chaching’ono (crosstalk) pafupipafupi, komanso umapanganso kusokonekera komwe kumayambitsidwa ndi nthaka posakhalitsa chizindikiro chilichonse chofunikira. Kapangidwe kocheperako mu Chithunzi 6 chikuwonetsa kuti mawonekedwe achiwiri amtundu wa harmonic komanso okwanira a harmonic (THD) amasintha kwambiri chifukwa chakuchotsa kwaposachedwa nthaka.

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Chidule cha nkhaniyi

Mwachidule, pa PCB, njira yobwerera m’mbuyo imadutsa pama capacitors osiyanasiyana (pazosiyanasiyana zamagetsi) ndi magetsi omwewo, ofanana ndi magwiridwe ake. Chizindikiro chapamwamba kwambiri chimayenda kubwerera ku capacitor yaying’ono. Ma frequency otsika pafupipafupi, monga ma audio, amatha kuyenda makamaka podutsa ma capacitors akuluakulu. Ngakhale ma frequency apansi pano “atha kunyalanyaza” kudumpha kwathunthu ndikudutsanso molunjika kutsogolera mphamvu. Kugwiritsa ntchito kwenikweni kudzatsimikizira njira yomwe ili yovuta kwambiri. 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.

Lamulo lagolide lokhazikitsidwa kwa HF PCB ndikusunga HF yolowera capacitor pafupi ndi pini yamagetsi momwe mungathere, koma kuyerekezera Chithunzi 5 ndi Chithunzi 6 kukuwonetsa kuti kusintha lamuloli kuti likhale ndi mawonekedwe osokonekera sikupanga kusiyana kulikonse. Makhalidwe abwino opotoka adadza chifukwa chowonjezera ma 0.15 mainchesi othamangitsa ma capacitor, koma izi sizinakhudze magwiridwe antchito a FHP3450. Kuyika kwa PCB ndikofunikira kuti kukulitsa magwiridwe antchito a zokulitsa zapamwamba, ndipo nkhani zomwe takambirana pano sizongokhala kwa ma hf amplifiers. Zizindikiro zam’munsi zocheperako monga zomvera zimafunikira kwambiri zopotoza. Zomwe zimachitika panthaka ndizocheperako pamafupipafupi, komabe zitha kukhala vuto lofunikira ngati cholozera cholakwika chikufunika bwino.