Tejede Circuit ọkọ awọn iṣoro iṣoro ati awọn solusan

Q: As mentioned earlier about simple resistors, there must be some resistors whose performance is exactly what we expect. What happens to the resistance of a section of wire?
A: The situation is different. Presumably you’re referring to a wire or a conductive band in a printed circuit board that acts as a wire. Since room-temperature superconductors are not yet available, any length of metal wire acts as a low-resistance resistor (which also acts as a capacitor and inductor), and its effect on the circuit must be considered.
2. Q: The resistance of a very short copper wire in a small signal circuit must not be important?
A: jẹ ki a gbero ADC 16-bit pẹlu ikọluwọle titẹsi ti 5k ω. Ro pe laini ifihan si titẹsi ADC ni oriširiši igbimọ Circuit ti a tẹjade (nipọn 0.038mm, 0.25mm jakejado) pẹlu ẹgbẹ adaṣe ti 10cm ni ipari. O ni resistance ti o to 0.18 ω ni iwọn otutu yara, eyiti o kere diẹ si 5K × × 2 × 2-16 ati pe o ṣe agbejade aṣiṣe ere ti 2LSB ni iwọn kikun.
Ni ijiyan, iṣoro yii le dinku bi o ba jẹ pe, bi o ti jẹ tẹlẹ, ẹgbẹ ifọrọhan ti igbimọ Circuit TITẸ ti di gbooro. Ni awọn iyika afọwọṣe, o jẹ igbagbogbo ni gbogbogbo lati lo ẹgbẹ ti o gbooro, ṣugbọn ọpọlọpọ awọn apẹẹrẹ PCB (ati awọn apẹẹrẹ PCB) fẹ lati lo iwọn ẹgbẹ ti o kere lati dẹrọ gbigbe laini ifihan. Ni ipari, o ṣe pataki lati ṣe iṣiro resistance ti ẹgbẹ adaṣe ati itupalẹ ipa rẹ ninu gbogbo awọn iṣoro ti o ṣeeṣe.
3. Q: Is there a problem with the capacitance of the conductive band with too large width and the metal layer on the back of the PRINTED circuit board?
A: It’s a small question. Although capacitance from the conductive band of the PRINTED circuit board is important (even for low-frequency circuits, which can produce high-frequency parasitic oscillations), it should always be estimated first. If this is not the case, even a wide conductive band forming a large capacitance is not a problem. If problems arise, a small area of the ground plane can be removed to reduce the capacitance to earth.
Q: Fi ibeere yii silẹ fun iṣẹju diẹ! Kini ọkọ ofurufu ti ilẹ?
A: Ti bankanje idẹ ni gbogbo ẹgbẹ ti igbimọ Circuit ti a tẹjade (tabi gbogbo interlayer ti igbimọ Circuit ti a tẹjade pupọ) ti lo fun ilẹ, lẹhinna eyi ni ohun ti a pe ni ọkọ ofurufu ilẹ. Eyikeyi okun waya ilẹ yoo wa ni idayatọ pẹlu itusilẹ ti o kere julọ ati inductance. Ti eto kan ba lo ọkọ ofurufu ilẹ, o kere julọ lati ni ipa nipasẹ ariwo ilẹ. Ni afikun, ọkọ ofurufu ilẹ tun ni iṣẹ ti aabo ati itutu agbaiye
Q: Ọkọ ofurufu ti a mẹnuba nibi jẹ nira fun awọn aṣelọpọ, otun?
A: Awọn iṣoro kan wa ni ọdun 20 sẹhin. Loni, nitori ilọsiwaju ti Apapo, resistance solder ati imọ -ẹrọ soldering igbi ni awọn igbimọ Circuit ti a tẹjade, iṣelọpọ ọkọ ofurufu ilẹ ti di iṣẹ ṣiṣe deede ti awọn igbimọ Circuit ti a tẹjade.
Q: O sọ pe o ṣeeṣe lati ṣafihan eto kan si ariwo ilẹ nipa lilo ọkọ ofurufu ilẹ jẹ kere pupọ. Kini o ku ninu iṣoro ariwo ilẹ ti ko le yanju?
A: Circuit ipilẹ ti eto ariwo ilẹ ti o ni ọkọ ofurufu ilẹ, ṣugbọn resistance ati ifilọlẹ rẹ kii ṣe odo – ti orisun lọwọlọwọ lọwọlọwọ ba lagbara to, yoo kan awọn ifihan agbara to pe. Iṣoro yii le dinku nipasẹ siseto awọn tabili Circuit ti a tẹjade daradara ki lọwọlọwọ giga ko ṣan si awọn agbegbe ti o ni ipa lori foliteji ilẹ ti awọn ifihan agbara to peye. Nigbakan isinmi tabi fifin ni ọkọ ofurufu ilẹ le yiyi ṣiṣan ilẹ nla nla lati agbegbe ifamọra, ṣugbọn fi agbara mu iyipada ọkọ ofurufu ilẹ tun le yi ifihan pada si agbegbe ti o ni imọlara, nitorinaa iru ilana bẹẹ gbọdọ lo pẹlu itọju.
Q: How do I know the voltage drop generated on a grounded plane?
A: nigbagbogbo fifuye foliteji le ṣee wọn, ṣugbọn nigbami awọn iṣiro le ṣee ṣe da lori resistance ti ohun elo ninu ọkọ ofurufu ilẹ (ipin 1 iwon idẹ kan ni resistance ti 045m ω /□) ati ipari ti ẹgbẹ adaṣe nipasẹ eyiti lọwọlọwọ kọja, botilẹjẹpe awọn iṣiro le jẹ idiju. Awọn foliteji ninu dc si ipo igbohunsafẹfẹ kekere (50kHz) ni a le wọn pẹlu awọn ohun elo ẹrọ bii AMP02 tabi AD620.
The amplifier gain was set at 1000 and connected to an oscilloscope with a sensitivity of 5mV/div. The amplifier may be supplied from the same power source as the circuit under test, or from its own power source. However, if the amplifier ground is separated from its power base, the oscilloscope must be connected to the power base of the power circuit used.
The resistance between any two points on the ground plane can be measured by adding a probe to the two points. The combination of amplifier gain and oscilloscope sensitivity enables the measurement sensitivity to reach 5μV/div. Noise from the amplifier will increase the width of the oscilloscope waveform curve by about 3μV, but it is still possible to achieve a resolution of about 1μV — enough to distinguish most ground noise with up to 80% confidence.
Q: What should be noted about the above test method?
A: Eyikeyi aaye oofa iyipo yoo ṣe okunfa foliteji kan lori adari iwadii, eyiti o le ṣe idanwo nipasẹ kikuru lilọ kiri awọn iwadii si ara wọn (ati pese ọna ipadabọ si resistance ilẹ) ati akiyesi wiwọn oscilloscope. Iwọn igbi AC ti a ṣe akiyesi jẹ nitori fifa irọbi ati pe o le dinku nipasẹ yiyipada ipo ti oludari tabi nipa igbiyanju lati yọkuro aaye oofa. Ni afikun, o jẹ dandan lati rii daju pe ipilẹ ti ampilifaya ti sopọ si ipilẹ ti eto naa. Ti ampilifaya ba ni asopọ yii ko si ọna ipadasẹhin ati pe ampilifaya kii yoo ṣiṣẹ. Ilẹ ilẹ yẹ ki o tun rii daju pe ọna ilẹ ti a lo ko ṣe dabaru pẹlu pinpin lọwọlọwọ ti Circuit labẹ idanwo.
Q: How to measure the high frequency grounding noise?
A: It is difficult to measure hf ground noise with a suitable wideband instrumentation amplifier, so hf and VHF passive probes are appropriate. It consists of a ferrite magnetic ring (outer diameter of 6 ~ 8mm) with two coils of 6 ~ 10 turns each. To form a high-frequency isolation transformer, one coil is connected to the spectrum analyzer input and the other to the probe.
Ọna idanwo jẹ iru si ọran igbohunsafẹfẹ kekere, ṣugbọn onínọmbà spectrum nlo awọn ọna abuda titobi-igbohunsafẹfẹ lati ṣe aṣoju ariwo. Ko dabi awọn ohun -ini agbegbe akoko, awọn orisun ariwo le ṣe iyatọ ni rọọrun da lori awọn abuda igbohunsafẹfẹ wọn. Ni afikun, ifamọra ti onitupalẹ iwoye ni o kere ju 60dB ti o ga ju ti oscilloscope broadband lọ.
Q: Kini nipa inductance ti okun waya kan?
A: Awọn inductance ti awọn oludari ati awọn ẹgbẹ adaṣe PCB ko le ṣe bikita ni awọn igbohunsafẹfẹ giga. Lati le ṣe iṣiro inductance ti okun waya taara ati ẹgbẹ adaṣe, awọn isunmọ meji ni a ṣafihan nibi.
For example, a conductive band 1cm long and 0.25mm wide will form an inductance of 10nH.
Conductor inductance = 0.0002LLN2LR-0.75 μH
Fun apẹẹrẹ, inductance ti 1cm gigun 0.5mm okun waya opin ita jẹ 7.26nh (2R = 0.5mm, L = 1cm)
Conductive band inductance = 0.0002LLN2LW +H+0.2235W+HL+0.5μH
Fun apẹẹrẹ, awọn inductance ti 1cm jakejado 0.25mm tejede Circuit igbimọ igbimọ eleto jẹ 9.59nh (H = 0.038mm, W = 0.25mm, L = 1cm).
Bibẹẹkọ, ifaseyin inductive nigbagbogbo kere pupọ ju ṣiṣan parasitic ati foliteji ti o fa ti Circuit inductive ti a ge. Agbegbe lupu gbọdọ wa ni idinku nitori foliteji ti o fa jẹ ibamu si agbegbe lupu. Eyi rọrun lati ṣe nigbati wiwakọ jẹ ayidayida-bata.
In printed circuit boards, the lead and return paths should be close together. Small wiring changes often minimize the impact, see source A coupled to low energy loop B.
Reducing the loop area or increasing the distance between the coupling loops will minimize the effect. The loop area is usually reduced to a minimum and the distance between the coupling loops is maximized. Magnetic shielding is sometimes required, but is expensive and prone to mechanical failure, so avoid it.
11. Q: In Q&A for Application Engineers, non-ideal behavior of integrated circuits is often mentioned. It should be easier to use simple components such as resistors. Explain the proximity of ideal components.
A: Mo kan fẹ ki alatako kan jẹ ẹrọ ti o peye, ṣugbọn silinda kukuru ti o wa ni iwaju alatako kan n ṣiṣẹ gangan bi alatako mimọ. Alatako gangan tun ni paati ifarada riro – paati ifaseyin. Pupọ awọn alatako ni agbara kekere (deede 1 si 3pF) ni afiwe pẹlu resistance wọn. Botilẹjẹpe diẹ ninu awọn alatako fiimu, gige gige yara bibẹrẹ ninu awọn fiimu resistive wọn jẹ ifilọlẹ pupọ julọ, ifesi ifunni wọn jẹ mewa tabi awọn ọgọọgọrun ti nahen (nH). Nitoribẹẹ, awọn itusilẹ ọgbẹ okun waya jẹ igbagbogbo ni agbara kuku ju agbara lọ (o kere ju ni awọn igbohunsafẹfẹ kekere). Lẹhinna, awọn alatako-ọgbẹ okun jẹ ti awọn okun, nitorinaa kii ṣe loorekoore fun awọn alatako-ọgbẹ okun lati ni awọn inductances ti ọpọlọpọ microhm (μH) tabi mewa ti microhm, tabi paapaa eyiti a pe ni “aisi-inductive” awọn alatako-ọgbẹ okun (nibiti idaji awọn iyipo ti wa ni ọgbẹ aago ati idaji keji ni ilodi si aago). Nitorinaa pe inductance ti iṣelọpọ nipasẹ awọn halves meji ti okun fagile ara wọn) tun ni 1μH tabi diẹ sii ti inductance ti o ku. Fun awọn alatako-okun waya ti o ni iye to ga ju 10k ω, awọn alatako ti o ku jẹ agbara pupọ ju kukisi lọ, ati pe agbara jẹ to 10pF, ti o ga ju ti fiimu tinrin boṣewa tabi awọn alatako sintetiki. A gbọdọ ṣe akiyesi ifesi yii ni pẹkipẹki nigbati o ṣe apẹrẹ awọn iyika igbohunsafẹfẹ giga ti o ni awọn alatako.
Q: Ṣugbọn ọpọlọpọ awọn iyika ti o ṣe apejuwe ni a lo fun awọn wiwọn deede ni DC tabi awọn igbohunsafẹfẹ pupọ. Awọn inductors ti o lọra ati awọn kapasito ti ko lọ ko ṣe pataki ninu awọn ohun elo wọnyi, otun?
A: bẹẹni. Nitori awọn transistors (mejeeji ọtọ ati laarin awọn iyika iṣọpọ) ni awọn iwọn igbohunsafẹfẹ pupọ, awọn oscillations le ma waye ni awọn ọgọọgọrun tabi ẹgbẹẹgbẹrun awọn ẹgbẹ megahertz nigbati Circuit dopin pẹlu fifuye inductive. Awọn aiṣedeede ati awọn iṣe atunse ti o ni nkan ṣe pẹlu awọn oscillations ni awọn ipa buburu lori iṣedede igbohunsafẹfẹ kekere ati iduroṣinṣin.
Ti o buru julọ, awọn oscillations le ma han lori oscilloscope boya nitori bandwidth ti oscilloscope ti kere pupọ ni akawe si bandiwidi ti awọn oscillations igbohunsafẹfẹ giga ti a wọn, tabi nitori agbara idiyele ti iwadii oscilloscope jẹ to lati da awọn oscillations duro. Ọna ti o dara julọ ni lati lo ẹgbẹ ti o gbooro (igbohunsafẹfẹ kekere si 15GHz loke) itupalẹ iwoye lati ṣayẹwo eto fun awọn oscillations parasitic. Ayẹwo yii yẹ ki o ṣee ṣe nigbati titẹ sii yatọ lori gbogbo sakani agbara, nitori awọn oscillations parasitic nigba miiran waye ni ibiti o dín pupọ ti ẹgbẹ titẹ sii.
Q: Ṣe awọn ibeere eyikeyi nipa awọn alatako?
A: The resistance of a resistor is not fixed, but varies with temperature. The temperature coefficient (TC) varies from a few PPM /°C(millionths per degree Celsius) to several thousand PPM /°C. The most stable resistors are wire wound or metal film resistors, and the worst are synthetic carbon film resistors.
Awọn isodipupo iwọn otutu ti o tobi le jẹ iwulo nigbakan (a +3500ppm/ ° C resistor le ṣee lo lati isanpada fun kT/ Q ni idogba abuda diode ipade, bi a ti mẹnuba tẹlẹ ni Q&AS fun Awọn Injinia Ohun elo). Ṣugbọn ni atako gbogbogbo pẹlu iwọn otutu le jẹ orisun aṣiṣe ni awọn iyika titọ.
Ti titọ ti Circuit da lori ibaamu ti awọn alatako meji pẹlu awọn isodipupo iwọn otutu ti o yatọ, lẹhinna laibikita baamu daradara ni iwọn otutu kan, kii yoo baamu ni ekeji. Paapa ti awọn ibawọn iwọn otutu ti awọn alatako meji ba baramu, ko si iṣeduro pe wọn yoo wa ni iwọn otutu kanna. Ara-ooru ti ipilẹṣẹ nipasẹ agbara agbara inu tabi ooru ita ti a gbejade lati orisun ooru ninu eto le fa aiṣedeede iwọn otutu, ti o yorisi resistance. Paapa ọgbẹ-didara okun waya tabi awọn alatako fiimu-irin le ni awọn aiṣedeede iwọn otutu ti awọn ọgọọgọrun (tabi paapaa ẹgbẹẹgbẹrun) PPM / ℃. Ojutu ti o han ni lati lo awọn alatako meji ti a ṣe ki wọn jẹ mejeeji sunmọ matrix kanna, ki iṣedede eto naa baamu daradara ni gbogbo igba. Sobusitireti le jẹ awọn wafer silikoni ti o ṣedasilẹ awọn iyika iṣọpọ kongẹ, awọn wafers gilasi tabi awọn fiimu irin. Laibikita sobusitireti, awọn alatako meji baamu daradara lakoko iṣelọpọ, ni awọn isodipupo iwọn otutu ti o baamu daradara, ati pe o fẹrẹ to iwọn otutu kanna (nitori wọn sunmọ to).