Saizvozvo, yakadhindwa redunhu bhodhi (PCB) zvakagadzirwa nemagetsi mitsara zvinhu, kureva kuti yavo impedance inofanira kugara. Saka nei pcb ichiunza nonlinearity muchiratidzo? Mhinduro ndeyekuti marongero ePCB ari “enzvimbo asiri emitsara” inoenderana nekwekuyerera kwazvino.

Kunyangwe iyo gudzazwi inogamuchira yazvino kubva kune imwe sosi kana imwe inoenderana neiyo pakarepo polarity yechiratidzo pane mutoro. Yazvino inoyerera ichibva pasimba remagetsi, kuburikidza neiyo yekupfuura capacitor, kuburikidza neyekuwedzera mumutoro. 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. Mune imwe ndege yepasi, panowanzo kuve neinopfuura imwe yakaderera-impedance nzira kuburikidza iyo yakakura chikamu chepasi parizvino kuyerera: imwe nzira yakabatana yakanangana neapass capacitor; Imwe yacho inonakidza yekupikisa resistor kudzamara iyo yekupfuura capacitor yasvika. Mufananidzo 1 unoratidzira idzi mbiri nzira. The backflow current is what’s really causing the problem.

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Kana yekupfuura ma capacitors ikaiswa munzvimbo dzakasiyana paPCB, iyo yepasi parizvino inoyerera nenzira dzakasiyana kuenda kune yakadarika kupfuura ma capacitors, inova iyo zvinoreva “nzvimbo isina kubatana”. 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. Kana iyo imwe polarity yevhu yazvino isina kukanganiswa, iyo yekuisa chiratidzo magetsi magetsi anochinja nenzira isina mutsetse. Kana imwe polarity chikamu yashandurwa asi imwe polarity isiri, kukanganisa kunoitika uye kunoratidzirwa sekukanganisa kwechipiri kweharmonic kwechiratidzo chinobuda. Mufananidzo 2 unoratidza kukanganisa uku mune akawedzeredzwa fomu.

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Kana imwechete polar chikamu cheiyo sine wave ichivhiringidzika, iyo inoguma waveform haisisiri sine wave. Kufananidza yakagadzika gadziriso ine zana-ω mutoro uye kubatanidza mutoro uripo kuburikidza ne100-ω resistor muvhu revhu pane imwechete polarity yechiratidzo, zvinoguma mufananidzo 1. Fourier transform shows that the distortion waveform is almost all the second harmonics at -68 DBC. Pakukwirira kwakawanda, iyi nhanho yekubatanidza inogadzirwa nyore nyore paPCB, iyo inogona kuparadza yakanakisa anti-kusanganisa hunhu hwechidzudziswi pasina kushandisa kune yakawanda yakakosha isina mutsetse mhedzisiro yePCB. 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

Dambudziko remazhinji-gudzazwi machipisi (maviri, matatu, kana mana maaplifaya) akawedzera nekusagona kuchengetedza kubatana kwepasi kweiyo yekupfuura capacitor kure nezvose zvinoiswa. Izvi zvinonyanya kuitika kune ma amplifaya mana. Quad-amplifier machipisi ane zviteshi zvekuisa padivi rega rega, saka hapana nzvimbo yemapaseti ekuderedza ayo anodzikisira kukanganiswa kune yekuisa chiteshi.

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Mufananidzo 5 unoratidza nzira yakapusa kune mana-gudzazwi dhizaini. Midziyo mizhinji inosangana yakanangana nequad gudzazwi pini. Iyo ivhu razvino rerimwe magetsi rinokwanisa kukanganisa iyo yekuisa ivhu voltage uye yepasi ikozvino yeiyo imwe chiteshi magetsi magetsi, zvichikonzera kukanganisa. Semuenzaniso, iyo (+ Vs) yekupfuura capacitor pane chiteshi 1 yeiyo quad amplifier inogona kuiswa yakanangana padhuze nekwairi kuisa; Iyo (-Vs) yekupfuura capacitor inogona kuiswa kune rimwe divi repakeji. Iyo (+ Vs) pasi yazvino inogona kukanganisa chiteshi 1, nepo (-vs) pasi pari zvino isingakwanise.

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Kuti udzivise dambudziko iri, rega pasi parizvino rikanganise iyo yekuisa, asi rega iyo pcb yazvino kuyerera mune yepakatially linear fashoni. Kuti uite izvi, yekudarika capacitor inogona kurongedzwa paPCB nenzira yekuti iyo (+ Vs) uye (- Vs) mafungu epasi anoyerera nenzira imwecheteyo. Kana chiratidzo chekupinza chakakanganiswa zvakaenzana nemasaisai akanaka uye asina kunaka, kukanganisa hakuzoitika. Naizvozvo, enzanisa iwo maviri ekupfuura ma capacitors padhuze nepadhuze kuti vagovane nzvimbo yepasi. Nekuti izvo zviviri polar zvinoumba zvepasi parizvino zvinobva panzvimbo imwechete (iyo inoburitsa chinobatanidza chengetedzo kana mutoro wepasi) uye ese ari maviri anoyerera achidzokera kunzvimbo imwechete (iyo yakajairika pasi kubatanidza yeiyo yekupfuura capacitor), iyo yakanaka / yakaipa yazvino inoyerera kuburikidza nzira imwe chete. Kana kupokana kwekuisa kwechaini kukanganiswa ne (+ Vs) zvazvino, (- Vs) zvazvino zvine zvazvinoita pairi. 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 uone kukosha kuri pamusoro apa, marongero maviri akasiyana ePBB akashandiswa: dhizaini yakapusa (Mufananidzo 5) uye dhizaini yekudzora (Mufananidzo 6). Iko kukanganisa kwakaburitswa neiyo FHP3450 quad-inoshanda gudzazwi ichishandisa fairchild semiconductor inoratidzwa mune tafura 1. Iyo chaiyo bandwidth yeiyo FHP3450 ndeye 210MHz, iko kutsvedza i1100V / isu, iko kwekusarura kwazvino kuri 100nA, uye iko iko kushanda pane chiteshi kuri 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. Zviripachena, yakapihwa gudzazwi gwara rinonetsekedza kwete iro chete rekuisa, asi kuiswa kweimwe nzira zvakare. The earth current flows through all the different channel inputs and produces different effects, but is influenced by each output, which is measurable.

Tafura yechipiri inoratidza maumboni anoyerwa pane dzimwe nzira dzisina kusvetwa kana chiteshi chimwe chete chichiendeswa. Iyo isina kubvumidzwa chiteshi inoratidza diki chiratidzo (crosstalk) pane yakakosha frequency, asi zvakare inogadzira kukanganisa kwakanangidzirwa kwakanangidzirwa nepasi razvino mukushaikwa kwechimwe chakakosha chiratidzo chiratidzo. Kurongeka kwekudzikira kwakadzika muMufananidzo 6 kunoratidza kuti yechipiri harmonic uye yakazara harmonic kukanganisa (THD) hunhu hwakagadziridzwa zvakanyanya nekuda kwekubvisa-kwepedyo kwepasi kuitika.

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Ichi chinyorwa pfupiso

Zvichitaurwa zviri nyore, pane pcbb, iyo yekudzokera parizvino inoyerera kuburikidza akasiyana ekupfuura maaccitors (kune akasiyana magetsi magetsi) uye magetsi emagetsi pachawo, zvinoenderana nekuitisa kwayo. Iyo yakakwira-frequency chiratidzo chazvino inoyerera ichidzokera kune idiki yekupfuura capacitor. Yakadzika-frequency masaisai, senge yeavo maodhiyo ekuteerera, anogona kuyerera zvakanyanya kuburikidza neakakura ekupfuura ma capacitors. Kunyangwe iyo yepazasi frequency yazvino inogona “kusaremekedza” iyo yakazara yekudarika capacitance uye kuyerera yakananga yakananga kune iro rinotungamira simba. Iyo chaiyo yekushandisa ichaona kuti ndeipi nzira yazvino inonyanya kukosha. 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.

Mutemo wegoridhe weiyo HF PCB dhizaini ndeyekuchengetedza iyo HF yekupfuura capacitor padhuze nepakaiswa simba pini sezvinobvira, asi kuenzanisa kweMufananidzo 5 uye Mufananidzo 6 unoratidza kuti kugadzirisa mutemo uyu kugadzirisa hunhu hwekukanganisa hakuite musiyano mukuru. Hunhu hwakagadziriswa hwekutsauka hwakauya pamubhadharo wekuwedzera nezve 0.15 inches yeakakwira-frequency ekupfuura capacitor wiring, asi izvi zvakange zvisina zvazvinobatsira pakuita kwe AC mhinduro yeFHP3450. Pcb magadzirirwo akakosha kuti awedzere mashandiro emhando yepamusoro gudzazwi, uye nyaya dzakurukurwa pano hadziganhurirwe ku hf amplifiers. Dzakadzika frequency masekisheni senge odhiyo ane zvakanyanya kuomarara kukanganisa. Iyo ivhu yazvino mhedzisiro idiki pane yakaderera mafurati, asi inogona kunge ichiri dambudziko rakakosha kana iyo inodiwa yekutsausa indekisi yakavandudzwa nenzira kwayo.