en>Mogism: Cleanup/Typo fixing, typo(s) fixed: Enroute → En route, 1940’s → 1940s (7) using AWB

2013-12-19T01:18:26Z

Cleanup/Typo fixing, typo(s) fixed: Enroute → En route, 1940’s → 1940s (7) using AWB

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{{more footnotes|date=June 2013}}

'''Effective number of bits''' ('''ENOB''') is a measure of the dynamic performance of an [[analog-to-digital converter]] (ADC) and its associated circuitry. The resolution of an ADC is specified by the number of [[bit]]s used to represent the analog value, in principle giving 2N signal levels for an N-bit signal. However, all real ADC circuits introduce [[Noise (electronics)|noise]] and [[distortion]]. ENOB specifies the resolution of an ideal ADC circuit that would have the same resolution as the circuit under consideration.

ENOB is also used as a quality measure for other blocks such as [[Sample and hold|sample-and-hold amplifiers]]. This way, analog blocks can be easily included in signal-chain calculations as the total ENOB of a chain of blocks is usually below the ENOB of the worst block.

==Definition==
An often used definition for ENOB is<ref>{{Harvnb|Kester|2009|p=5}}, Equation 1.</ref>
:<math>\mathrm{ENOB} = \frac{\mathrm{SINAD}-1.76}{6.02}</math>,
where all values are given in dB and:
* [[SINAD]] is the ratio indicating the quality of the signal.
* The 6.02 term in the divisor converts [[decibels]] (a log10 representation) to bits (a log2 representation).<ref group=note><math>6.02 \approx 20 \log_{10}2</math></ref>
* The 1.76 term comes from quantization error in an ideal ADC.{{#tag:ref |<math>1.76 \approx 10 \log_{10}\left( 3/2 \right)</math><ref>Eq. 2.8 in "Design of multi-bit delta-sigma A/D converters", Yves Geerts, Michiel Steyaert, Willy M. C. Sansen, 2002.</ref>|group=note}}

This definition compares the SINAD of an ideal ADC or DAC with a word length of ENOB bits with the SINAD of the ADC or DAC being tested.

==See also==
*[[Signal-to-noise ratio]]

==Notes==
{{reflist|group=note}}

==References==
{{Reflist}}
* {{Cite book
| last = Gielen
| first = Georges
| title = Analog Building Blocks for Signal Processing
| publisher = KULeuven-ESAT-MICAS
| location = Leuven
| year = 2006
}}
*{{Citation
|last= Kester
|first= Walt
|title= Understand SINAD, ENOB, SNR, THD, THD + N, and SFDR so You Don't Get Lost in the Noise Floor
|url= http://www.analog.com/static/imported-files/tutorials/MT-003.pdf
|publisher= Analog Devices
|year= 2009
|series=Tutorial
|id=MT-003
|doi=}}
*{{Citation
|last= Maxim
|first=
|title= Glossary of Frequently Used High-Speed Data Converter Terms
|url=http://www.maxim-ic.com/appnotes.cfm/appnote_number/740/
|date= December 17, 2001
|publisher=Maxim
|series=Application Note
|id= 740
|doi=}}

==External links==
* [http://e2e.ti.com/videos/m/analog/97246.aspx Video tutorial on ENOB] from Texas Instruments
* [http://www.rohde-schwarz.com/appnote/1ER03.pdf The Effective Number of Bits (ENOB)] - This application note explains how to measure the oscilloscope ENOB.

{{Noise}}

{{DEFAULTSORT:Enob}}
[[Category:Digital signal processing]]
[[Category:Noise]]
[[Category:Measurement]]

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en>Mogism: Cleanup/Typo fixing, typo(s) fixed: Enroute → En route, 1940’s → 1940s (7) using AWB