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Digital-to-analog converter
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==Types== The most common types of electronic DACs are:<ref name="ADDCH">{{cite web |url=http://www.analog.com/media/en/training-seminars/design-handbooks/Data-Conversion-Handbook/Chapter3.pdf |title=Data Converter Architectures |work=Analog-Digital Conversion |publisher=[[Analog Devices]] |access-date=2017-08-30 |df=ymd-all |ref={{sfnref|"Data Converter Architectures"}}|url-status=live |archive-url=https://web.archive.org/web/20170830032212/http://www.analog.com/media/en/training-seminars/design-handbooks/Data-Conversion-Handbook/Chapter3.pdf |archive-date=2017-08-30}}</ref> * The [[pulse-width modulator]] where a stable [[current (electricity)|current]] or [[voltage]] is switched into a low-pass [[analog filter]] with a duration determined by the digital input code. This technique is often used for [[Motor controller|electric motor speed control]] and dimming [[LED lamp]]s. * Oversampling DACs or interpolating DACs such as those employing [[delta-sigma modulation]], use a pulse density conversion technique with [[oversampling]]. Audio delta-sigma DACs are sold with 384 kHz sampling rate and quoted 24-bit resolution, though quality is lower due to inherent noise (see {{Slink|2=Figures of merit|nopage=y}}). Some consumer electronics use a type of oversampling DAC referred to as a [[1-bit DAC]]. * The binary-weighted DAC, which contains individual electrical components for each bit of the DAC connected to a summing point, typically an [[operational amplifier]]. Each input in the summing has powers-of-two weighting with the most current or voltage at the [[most-significant bit]]. This is one of the fastest conversion methods but suffers from poor accuracy because of the high precision required for each individual voltage or current.<ref>{{Cite web |url=https://www.electronics-tutorial.net/analog-integrated-circuits/data-converters/binary-weighted-resistor-dac/index.html |title=Binary Weighted Resistor DAC |website=Electronics Tutorial |language=en-US |access-date=2018-09-25 |df=ymd-all}}</ref> ** Switched [[resistor]] DAC contains a parallel resistor network. Individual resistors are enabled or bypassed in the network based on the digital input. ** Switched [[current source]] DAC, from which different current sources are selected based on the digital input. [[File:DAC-1138KX - pcb top view.jpg|thumb|Current steering DAC - DAC1138KX]] ** Switched [[capacitor]] DAC contains a parallel capacitor network. Individual capacitors are connected or disconnected with switches based on the input. ** The [[resistor ladder|R-2R ladder]] DAC which is a binary-weighted DAC that uses a repeating cascaded structure of resistor values R and 2R. This improves the precision due to the relative ease of producing equal valued-matched resistors. * The successive approximation or cyclic DAC,{{sfn|"Data Converter Architectures"|p=3.29}} which successively constructs the output during each cycle. Individual bits of the digital input are processed each cycle until the entire input is accounted for. * The [[Thermometer code|thermometer-coded]] DAC, which contains an equal resistor or current-source segment for each possible value of DAC output. An 8-bit thermometer DAC would have 255 segments, and a 16-bit thermometer DAC would have 65,535 segments. This is a fast and highest precision DAC architecture but at the expense of requiring many components which, for practical implementations, fabrication requires high-density [[Semiconductor device fabrication|IC processes]].<ref>{{Citation |url=https://www.analog.com/media/en/training-seminars/tutorials/MT-014.pdf |archive-url=https://web.archive.org/web/20150503154823/http://www.analog.com/media/en/training-seminars/tutorials/MT-014.pdf |archive-date=2015-05-03 |url-status=live |author=Walt Kester |title=Basic DAC Architectures I: String DACs and Thermometer (Fully Decoded) DACs |publisher=[[Analog Devices]]}}</ref> * Hybrid DACs, which use a combination of the above techniques in a single converter. Most DAC integrated circuits are of this type due to the difficulty of getting low cost, high speed and high precision in one device. ** The segmented DAC, which combines the thermometer-coded principle for the most significant bits and the binary-weighted principle for the least significant bits. In this way, a compromise is obtained between precision (by the use of the thermometer-coded principle) and number of resistors or current sources (by the use of the binary-weighted principle). The full binary-weighted design means 0% segmentation, the full thermometer-coded design means 100% segmentation. * Most DACs shown in this list rely on a constant reference voltage or current to create their output value. Alternatively, a ''multiplying DAC''<ref>{{cite web |url=https://www.analog.com/media/en/news-marketing-collateral/solutions-bulletins-brochures/AnalogMultiplyingDACs.pdf |archive-url=https://web.archive.org/web/20110516075112/http://www.analog.com/static/imported-files/overviews/AnalogMultiplyingDACs.pdf |archive-date=2011-05-16 |url-status=live |title=Multiplying DACs: Flexible Building Blocks |year=2010 |publisher=[[Analog Devices]] |access-date=29 March 2012 |df=ymd-all}}</ref> takes a variable input voltage or current as a conversion reference. This puts additional design constraints on the bandwidth of the conversion circuit. * Modern high-speed DACs have an interleaved architecture, in which multiple DAC cores are used in parallel. Their output signals are combined in the analog domain to enhance the performance of the combined DAC.<ref>{{Cite book|title=Interleaving Concepts for Digital-to-Analog Converters: Algorithms, Models, Simulations and Experiments|last=Schmidt|first=Christian|date=2020|publisher=Springer Fachmedien Wiesbaden|isbn=9783658272630|location=Wiesbaden|language=en|doi=10.1007/978-3-658-27264-7|s2cid=199586286}}</ref> The combination of the signals can be performed either in the time domain or in the frequency domain.
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