Hauv hluav taws xob, DAC Circuit Court yog ib hom kab ke. Nws yog nws uas hloov cov teeb liab digital rau analog.
Muaj ntau lub voj voog DAC. Kev tsim nyog rau ib daim ntawv thov tshwj xeeb yog txiav txim siab los ntawm kev ntsuas zoo nrog rau kev daws teeb meem, tus qauv siab tshaj plaws, thiab lwm yam.
Digital-rau-analogue hloov dua siab tshiab tuaj yeem txo qhov kev xa tawm ntawm lub teeb liab, yog li nws yog qhov tsim nyog los nrhiav cov cuab yeej uas muaj qhov yuam kev me me ntawm daim ntawv thov.
Applications
DACs feem ntau yog siv rau hauv cov suab paj nruag los hloov cov ntaub ntawv xov tooj mus rau hauv cov cim suab analog. Lawv kuj tau siv hauv TV thiab xov tooj ntawm tes los hloov cov ntaub ntawv video rau hauv cov teeb liab video, feem, uas txuas nrog lub vijtsam tsav los tso saib cov duab monochromatic lossis ntau xim.
Nws yog ob daim ntawv thov no uas siv DAC circuits ntawm qhov kawg ntawm kev sib haum xeeb ntawm qhov ceev thiab pixel suav. Suab yog hom tsawg zaus nrog cov kev daws teeb meem siab thiab yees duab yog qhov sib txawv ntawm qhov sib txawv nrog cov duab qis mus rau nruab nrab.
Vim qhov nyuaj thiab qhov xav tau kom ua tib zoo sib koom ua ke, tag nrho tab sis DACs tshwj xeeb tshaj plaws tau ua raws li kev sib koom ua ke (ICs). Cov kev sib txuas tsis sib xws yog feem ntau nrawm heev, tsis muaj kev daws teeb meem, hom kev txuag hluav taws xob uas siv hauv cov tub rog radar systems. Cov cuab yeej ntsuas kev kub ceev heev, tshwj xeeb tshaj yog cov qauv oscilloscopes, kuj tuaj yeem siv cov DACs discrete.
Kev Qhia
Cov khoom ib nrab ntawm cov khoom siv tsis tu ncua ntawm DAC yog tsim rau yuav luag txhua lub cuab yeej, thiab cov duab thawj zaug lossis qhov kawg bandwidth ntawm tus qauv tsim smoothes lub suab teb rau hauv qhov nkhaus txuas ntxiv.
Teb cov lus nug: "DAC yog dab tsi?", nws tsim nyog sau cia tias cov khoom siv no hloov pauv tus lej paub daws teeb meem (feem ntau yog tus lej binary tas li) rau hauv tus nqi ntawm lub cev (piv txwv li, voltage lossis siab). Tshwj xeeb, D/A hloov dua siab tshiab feem ntau yog siv los hloov lub sij hawm series cov ntaub ntawv mus rau ib tug tsis tu ncua hloov lub cev teeb liab.
Qhov zoo tshaj DAC hloov cov lej paub daws teeb rau hauv lub tswv yim tsheb ciav hlau ntawm pulses, uas tom qab ntawd ua tiav los ntawm kev tsim kho tshiab, siv qee hom kev cuam tshuam los sau cov ntaub ntawv ntawm pulses. Ib txwmlub tswv yim digital-rau-analogue converter hloov cov lej rau hauv ib qho kev ua haujlwm tas mus li ua los ntawm cov qauv ntawm cov duab plaub uas tau tsim tuav lub zeroth xaj. Tsis tas li ntawd, teb cov lus nug, "DAC yog dab tsi?" Nws yog tsim nyog sau cia lwm txoj kev (piv txwv li, raws li delta-sigma modulation). Lawv tsim cov mem tes-density modulated tso zis uas tuaj yeem lim tau zoo sib xws los tsim cov teeb liab sib txawv.
Raws li Nyquist-Shannon sampling theorem, DAC tuaj yeem tsim kho qhov qub vibration los ntawm cov ntaub ntawv coj mus kuaj, muab tias nws qhov nkag mus tau raws li qee qhov yuav tsum tau ua (piv txwv li, lub hauv paus mem tes nrog cov kab qis dua). Cov qauv digital sawv cev rau qhov yuam kev quantization, uas zoo li cov suab nrov qis hauv lub teeb liab rov tsim dua.
Daim duab ua haujlwm yooj yim ntawm 8-ntsis cuab yeej
Nws tsim nyog sau cia tam sim ntawd tias tus qauv nrov tshaj plaws yog Real Cable NANO-DAC digital-rau-analogue converter. Lub DAC yog ib feem ntawm kev siv thev naus laus zis uas tau ua rau muaj txiaj ntsig zoo rau kev hloov pauv digital. Txhawm rau ua piv txwv, xav txog kev hu xovtooj ntev ntev.
Tus hu lub suab tau hloov mus rau hauv lub teeb liab analog hluav taws xob siv lub microphone, thiab tom qab ntawd cov mem tes no tau hloov mus rau hauv cov kwj digital nrog rau DAC. Tom qab ntawd, tom kawg tau muab faib ua cov pob ntawv network, qhov twg nws tuaj yeem xa nrog rau lwm cov ntaub ntawv digital. Thiab nws yuav tsis tas yuav yog suab.
Tom qab ntawd pobraug lees txais ntawm qhov chaw, tab sis txhua tus ntawm lawv yuav siv txoj kev sib txawv kiag li thiab tsis tuaj yeem mus txog qhov chaw nyob hauv qhov kev txiav txim kom raug thiab raws sijhawm. Cov ntaub ntawv suab digital yog tom qab ntawd muab rho tawm los ntawm cov pob ntawv thiab sib sau ua ke rau hauv cov ntaub ntawv sib xws. Lub DAC hloov qhov no rov qab mus rau hauv lub teeb liab analog hluav taws xob uas tsav lub suab amplifier (xws li Real Cable NANO-DAC digital-to-analog converter). Thiab nws, tig, qhib lub suab nrov, uas thaum kawg tsim lub suab tsim nyog.
Audio
Cov suab paj nruag niaj hnub no feem ntau khaws cia digitally (xws li MP3 thiab CD). Yuav kom hnov los ntawm cov neeg hais lus, lawv yuav tsum tau hloov mus ua ib qho kev xav zoo sib xws. Yog li koj tuaj yeem nrhiav tau lub digital-rau-analog converter rau TV, CD player, digital music systems thiab PC sound cards.
Dedicated standalone DACs kuj tuaj yeem pom hauv cov tshuab Hi-Fi zoo. Lawv feem ntau siv cov khoom tso tawm digital ntawm tus neeg siv CD sib xws lossis lub tsheb siab thiab hloov lub teeb liab mus rau ib kab-qib analog tso zis uas tuaj yeem muab pub rau hauv lub tshuab hluav taws xob los tsav cov neeg hais lus.
Zoo D/A converters tuaj yeem pom hauv cov kab xws li USB hais lus thiab suab phaib.
Nyob rau hauv Voice over IP daim ntawv thov, lub hauv paus yuav tsum xub muab digitized rau kev sib kis, yog li nws tau hloov dua siab tshiab ntawm ADC thiab tom qab ntawd hloov mus rau analog siv DAC ntawmtog txais. Piv txwv li, txoj kev no yog siv rau qee qhov digital-rau-analog converters (TV).
Daim duab
Sampling nyiam ua haujlwm ntawm qhov sib txawv kiag li tag nrho, vim yog cov lus teb tsis zoo ntawm ob txoj kab hluav taws xob cathode (uas feem ntau ntawm cov yeeb yaj kiab digital tau tsim los rau) thiab tib neeg lub qhov muag, siv lub gamma nkhaus los muab cov tsos ntawm tusyees faib brightness cov kauj ruam hla tag nrho cov dynamic ntau ntawm cov zaub. Li no qhov yuav tsum tau siv RAMDAC hauv computer video daim ntawv thov nrog rau qhov sib sib zog nqus xim daws teeb meem, yog li ntawd nws yog ib qho tsim nyog los tsim ib qho nyuaj-coded tus nqi hauv DAC rau txhua theem tso zis ntawm txhua channel (piv txwv li, Atari ST lossis Sega Genesis yuav. xav tau 24 ntawm cov nqi no; 24-ntsis daim npav video yuav xav tau 768).
Muab qhov kev hloov pauv tsis zoo no, nws tsis yog qhov tsis yooj yim rau TV lossis video projector tau hais tseeb kom muaj qhov sib txawv ntawm qhov sib piv (qhov sib txawv ntawm qhov tsaus ntuj tshaj plaws thiab ci ntsa iab tshaj tawm qib) ntawm 1,000: 1 lossis ntau dua. Qhov no yog sib npaug rau 10 cov khoom ntawm lub suab fidelity, txawm tias nws tsuas tuaj yeem tau txais cov cim nrog 8-ntsis kev ncaj ncees thiab siv lub LCD vaj huam sib luag uas tsuas yog qhia txog rau los yog xya yam ntawm ib channel. DAC tshuaj xyuas tau luam tawm raws li qhov no.
Video signals los ntawm qhov chaw digital xws li lub khoos phis tawj yuav tsum tau hloov mus rau hauv daim ntawv analog yog tias lawv yuav tsum tau muab tso rau ntawm lub monitor. Zoo sib xws txij li xyoo 2007inputs tau siv ntau zaus dua li cov digital, tab sis qhov no tau hloov pauv raws li lub vaj huam sib luag tiaj tiaj nrog DVI lossis HDMI kev sib txuas tau dhau los ua ntau dua. Txawm li cas los xij, video DAC yog tsim rau hauv ib qho digital video player nrog tib cov txiaj ntsig. Ib qho digital-rau-analog lub converter feem ntau yog ua ke nrog qee yam kev nco (RAM) uas muaj cov rooj rov tsim kho rau kev kho gamma, qhov sib piv, thiab ci ntsa iab los tsim lub fixture hu ua RAMDAC.
Cov cuab yeej uas txuas nrog rau DAC yog lub tshuab hluav taws xob digitally tswj tau siv los khaws cov teeb liab.
Mechanical design
Piv txwv li, lub tshuab ntaus ntawv IBM Selectric twb siv DAC uas tsis yog phau ntawv los tsav lub pob.
Digital-rau-analogue converter circuit zoo li qhov no.
Ib-ntsis tshuab tsav siv ob txoj haujlwm: ib qho thaum qhib, lwm qhov thaum muab tua. Qhov kev txav ntawm ntau lub me me actuators tuaj yeem ua ke thiab hnyav los ntawm lub cuab yeej yam tsis muaj hesitation kom tau txais cov kauj ruam tseeb dua.
Nws yog IBM Selectric tshuab ntaus ntawv uas siv cov txheej txheem zoo li no.
hom tseem ceeb ntawm digital-rau-analog converters
- Pulse width modulator qhov twg qhov ruaj khov tam sim no lossis qhov hluav taws xob hloov pauv mus rau qhov ntsuas qis qis qis nrog lub sijhawm txiav txim siab los ntawm cov lej nkag digital. Txoj kev no feem ntau siv los tswj lub cev muaj zog ceev thiab dim LED teeb.
- Digital rau analog audio converter nrogoversampling los yog interpolating DACs, xws li cov neeg siv delta-sigma modulation, siv cov pulse density variation method. Ceev tshaj 100 ksample ib ob (piv txwv li 180 kHz) thiab 28-ntsis kev daws teeb meem yog ua tiav nrog delta-sigma ntaus ntawv.
- A binary weighted element uas muaj cov khoom hluav taws xob sib cais rau txhua qhov DAC me ntsis txuas nrog lub ntsiab lus xaus. Nws yog nws leej twg tuaj yeem ntxiv qhov ua haujlwm amplifier. Lub zog tam sim no ntawm qhov chaw yog proportional rau qhov hnyav ntawm qhov me me uas nws sib haum. Yog li, tag nrho cov khoom tsis yog xoom ntawm cov lej raug ntxiv rau qhov hnyav. Qhov no yog vim lawv muaj tib qhov voltage qhov chaw ntawm lawv pov tseg. Qhov no yog ib txoj kev hloov pauv sai tshaj plaws, tab sis nws tsis zoo tag nrho. Txij li thaum muaj ib qho teeb meem: tsis tshua muaj kev ntseeg siab vim yog cov ntaub ntawv loj uas yuav tsum tau muaj rau txhua tus neeg voltage lossis tam sim no. Xws li cov khoom siv high-precision yog kim, yog li hom qauv no feem ntau txwv rau 8-ntsis daws teeb meem lossis tsawg dua. Lub switched resistor muaj lub hom phiaj ntawm digital-rau-analog converters nyob rau hauv parallel network qhov chaw. Cov xwm txheej ntawm tus kheej tau txuas nrog hluav taws xob raws li cov khoom siv digital. Lub hauv paus ntsiab lus ntawm kev ua haujlwm ntawm hom digital-rau-analog converter no nyob hauv qhov hloov pauv tam sim no ntawm DAC, los ntawm cov yuam sij sib txawv raug xaiv raws li tus lej nkag. Nws muaj xws li ib tug synchronous capacitor kab. Cov ntsiab lus ib leeg txuas nrog lossis txiav tawm siv lub tshuab tshwj xeeb (ko taw) uas nyob ze txhua qhov ntsaws.
- Digital-rau-analogue stairway convertershom, uas yog binary-weighted element. Nws, nyob rau hauv lem, siv ib tug rov qab qauv ntawm lub cascaded resistor qhov tseem ceeb R thiab 2R. Qhov no txhim kho qhov tseeb vim qhov txheeb ze yooj yim ntawm kev tsim ntawm tib lub ntsuas ntsuas (lossis cov peev txheej tam sim no).
- Kev ua ntej lossis cyclic DAC uas tsim cov zis ib los ntawm ib qho ntawm txhua kauj ruam. Cov khoom ntawm tus kheej ntawm cov tswv yim digital tau ua tiav los ntawm txhua qhov txuas mus txog thaum tag nrho cov khoom raug suav rau.
- ntsuas ntsuas kub yog coded DAC uas muaj qhov sib npaug ntawm qhov sib npaug lossis ntu tam sim no rau txhua tus nqi ntawm DAC cov zis. 8-ntsis tus pas ntsuas kub DAC yuav muaj 255 yam, thiab 16-ntsis tus pas ntsuas kub DAC yuav muaj 65,535 qhov chaw. Qhov no yog kab tias ceev tshaj plaws thiab raug DAC architecture, tab sis ntawm tus nqi siab. Nrog rau hom DAC no, kev hloov pauv ntau dua ib txhiab tus qauv ib ob tau ua tiav.
- Hybrid DACs uas siv kev sib xyaw ua ke ntawm cov txheej txheem saum toj no hauv ib lub converter. Feem ntau DAC ICs yog hom no vim qhov nyuaj ntawm kev tau txais tus nqi qis, kev kub ceev, thiab qhov tseeb tag nrho hauv ib lub cuab yeej.
- Segmented DAC uas muab cov ntsiab lus ntawm tus ntsuas ntsuas ntsuas ntsuas rau cov lej siab dua thiab qhov hnyav binary rau cov khoom qis. Nyob rau hauv txoj kev no, muaj kev sib haum xeeb ntawm qhov raug (siv tus pas ntsuas kub coding txoj cai) thiab tus naj npawb ntawm cov resistors los yog tam sim no qhov chaw (siv binary weighting). Sib sib zog nqus ntaus ntawv nrog obkev txiav txim txhais tau tias segmentation yog 0%, thiab tsim nrog tag nrho cov thermometric coding muaj 100%.
Feem ntau ntawm DACS ntawm daim ntawv teev npe no vam khom qhov kev siv hluav taws xob tas li los tsim lawv cov nqi tso tawm. Xwb, qhov multiplying DAC txais AC input voltage los hloov lawv. Qhov no imposes ntxiv tsim txwv nyob rau hauv lub bandwidth ntawm lub reorganization tswvyim. Tam sim no nws paub meej tias vim li cas cov digital-rau-analog converters ntawm ntau hom xav tau.
Kev ua haujlwm
DACs tseem ceeb heev rau kev ua haujlwm ntawm lub cev. Cov yam ntxwv tseem ceeb tshaj plaws ntawm cov khoom siv no yog qhov kev daws teeb meem uas tsim los rau kev siv digital-rau-analog converter.
Tus naj npawb ntawm cov zis theem uas DAC tau tsim los ua si feem ntau tau teev raws li tus lej ntawm cov khoom siv, uas yog lub hauv paus ob lub logarithm ntawm cov qib. Piv txwv li, 1-ntsis DAC yog tsim los ua si ob lub voj voog, thaum 8-ntsis DAC yog tsim los ua si 256 circuits. Cov padding muaj feem cuam tshuam rau cov khoom siv tau zoo, uas yog qhov ntsuas ntawm qhov kev daws teeb meem tiag tiag ua tiav los ntawm DAC. Kev daws teeb meem txiav txim siab xim qhov tob hauv daim ntawv thov video thiab lub suab qis hauv cov khoom siv suab.
Max zaus
ntsuas qhov ceev tshaj plaws ntawm DAC Circuit Court tuaj yeem ua haujlwm ntawm thiab tseem tsim cov khoom tso tawm kom raug txiav txim siab txog kev sib raug zoo ntawm nws thiab bandwidth ntawm cov qauv teeb liab. Raws li tau hais los saum no, theoremNyquist-Shannon cov qauv cuam tshuam txog kev txuas ntxiv thiab tsis sib xws thiab thov tias txhua lub teeb liab tuaj yeem rov tsim dua nrog qhov tseeb los ntawm nws cov ntaub ntawv tsis sib xws.
Monotonicity
Lub tswv yim no yog hais txog lub peev xwm ntawm DAC cov zis analog tawm kom txav mus rau qhov kev taw qhia uas cov tswv yim digital txav. Cov yam ntxwv no tseem ceeb heev rau DACs siv los ua lub teeb liab tsawg zaus.
Txhua yam sib txawv thiab lub suab nrov (THD + N)
Kev ntsuas qhov tsis sib haum xeeb thiab lub suab nrov tshaj tawm los ntawm DAC rau hauv lub teeb liab, qhia raws li feem pua ntawm tag nrho cov nyiaj tsis xav tau kev sib haum xeeb thiab lub suab nrov uas nrog cov teeb liab xav tau. Qhov no yog ib qho tseem ceeb heev rau dynamic thiab tso zis tsawg DAC daim ntaub ntawv.
Ntaus
Kev ntsuas qhov sib txawv ntawm qhov loj tshaj plaws thiab me tshaj cov cim DAC tuaj yeem tsim tawm, qhia hauv decibels, feem ntau cuam tshuam txog kev daws teeb meem thiab suab nrov.
Lwm kev ntsuas xws li theem distortion thiab jitter kuj tseem ceeb heev rau qee qhov kev siv. Muaj cov (piv txwv li, wireless cov ntaub ntawv kis tau tus mob, composite video) uas muaj peev xwm txawm cia siab rau qhov tseeb tau txais theem-hloov teeb liab.
Linear PCM suab sampling feem ntau ua haujlwm ntawm qhov kev daws teeb meem ntawm txhua qhov sib npaug rau rau decibels ntawm amplitude (ob npaug ntawm qhov ntim lossis qhov tseeb).
Nonlinear PCM encodings (A-txoj cai / Μ-law, ADPCM, NICAM) sim txhim kho lawv cov kev ua haujlwm zoo hauv ntau txoj hauv kev -cov kauj ruam logarithmic qhov ntau thiab tsawg ntawm cov zis suab sawv cev los ntawm txhua cov ntaub ntawv me ntsis.
Kev faib tawm ntawm digital-rau-analog converters
Kev faib tawm los ntawm kev tsis sib xws faib faib ua:
- Distinctive non-linearity, uas qhia tau hais tias yuav ua li cas ob tug nyob sib ze code qhov tseem ceeb deviate los ntawm lub zoo meej 1 LSB kauj ruam.
- Cumulative non-linearity qhia tias deb npaum li cas DAC kis tau tus mob deviates los ntawm qhov zoo tagnrho.
Yog li qhov zoo tshaj plaws feature feem ntau yog txoj kab ncaj nraim. INL qhia ntau npaum li cas qhov hluav taws xob tiag tiag ntawm tus nqi code txawv ntawm cov kab no hauv qhov tsawg kawg nkaus.
Boost
Thaum kawg lub suab nrov yog txwv los ntawm thermal hum generated los ntawm passive Cheebtsam xws li resistors. Rau cov ntawv thov suab thiab hauv chav tsev kub, qhov no feem ntau tsuas yog qis dua 1 µV (microvolt) ntawm cov teeb liab dawb. Qhov no txwv kev ua haujlwm tsawg dua 20 khoom txawm tias hauv 24-ntsis DACs.
Kev ua tau zoo hauv qhov chaw zaus
Spurious-free dynamic range (SFDR) qhia nyob rau hauv dB qhov piv ntawm lub hwj chim ntawm lub ntsiab lub teeb liab hloov mus rau qhov loj tshaj plaws tsis xav overshoot.
Noise Distortion Ratio (SNDR) qhia hauv dB lub zog khoom ntawm lub suab hloov pauv loj rau nws cov lej.
Tag nrho kev sib haum xeeb distortion (THD) yog qhov suav ntawm lub zog ntawm tag nrho HDi.
Yog tias qhov yuam kev DNL siab tshaj plaws tsawg dua 1 LSB, ces tus hloov pauv digital-rau-analog tau lavyuav uniform. Txawm li cas los xij, ntau cov twj paj nruag monotonic tuaj yeem muaj qhov siab tshaj plaws DNL ntau dua 1 LSB.
Sijhawm domain kev ua haujlwm:
- Glitch impulse tsam (glitch zog).
- Tsis paub meej ntawm cov lus teb.
- Nonlinearity time (TNL).
DAC Basic Operations
Ib qho analog-rau-digital converter siv tus lej pes tsawg (feem ntau yog tus lej binary ruaj khov) thiab hloov nws mus rau hauv lub cev kom muaj nuj nqis (xws li voltage lossis siab). DACs feem ntau yog siv los hloov kho cov ntaub ntawv tshwj xeeb lub sij hawm series cov ntaub ntawv mus rau hauv lub cev hloov pauv tsis tu ncua.
Qhov zoo tshaj plaws D / A converter siv cov lej paub daws teeb meem los ntawm lub tsheb ciav hlau ntawm pulses, uas tom qab ntawd ua tiav siv daim ntawv ntawm kev sib cuam tshuam los sau cov ntaub ntawv ntawm cov teeb liab. Ib qho piv txwv digital-rau-analogue converter muab cov lej tso rau hauv ib qho kev ua haujlwm tas li uas muaj qhov sib lawv liag ntawm cov nqi sib npaug, uas yog qauv nrog xoom xaj tuav.
Lub converter rov kho cov cim qub kom nws cov bandwidth ua tau raws li qee qhov yuav tsum tau ua. Cov qauv digital yog nrog los ntawm quantization yuam kev uas tsim cov suab nrov qis. Nws yog nws leej twg ntxiv rau lub teeb liab rov qab. Qhov tsawg kawg nkaus amplitude ntawm lub suab analog uas tuaj yeem ua rau lub suab digital hloov pauv yog hu ua qhov tseem ceeb me ntsis (LSB). Thiab qhov yuam kev (rounding) uas tshwm sim ntawm cov cim analog thiab digital,hu ua quantization yuam kev.
