Effective number of bits

The effective number of bits (engl. Effective number of bits ; ENOB) indicates how high the actual resolution of an A / D or D / A converter is.

A / D and D / A converters commonly used today work with a fixed resolution of between 8 and 24 bits. When the analog data is recorded and then converted into digital data, measurement errors are caused not only by quantization but also by distortion and noise , e.g. B. when amplifying the signal. This reduces the theoretical maximum resolution of a converter.

In the case of A / D converters, the effective number of bits is calculated by feeding a sinusoidal signal with full level into the converter and then calculating the actual resolution based on the deviation from the target.

Calculation in logarithmic sizes ( decibels) :

{\ displaystyle \ mathrm {ENOB} \ mid _ {\ text {Bit}} = {\ frac {\ mathrm {SINAD \ mid _ {dB} -1 {,} 76 \, \ mathrm {dB}}} {6 {,} 02 \, \ mathrm {dB}}}}

The total interference ( SINAD ) results from the total harmonic distortion and the signal-to-noise ratio .

Individual evidence

↑ Walt Kester: Understand SINAD, ENOB, SNR, THD, THD + N, and SFDR so You Don't Get Lost in the Noise Floor. (pdf; 95 kB) Analog Devices, October 1, 2008, p. 5 , accessed on September 6, 2010 (English).

Web links

Measuring of dynamic figures: SNR, THD, SFDR. (PDF; 125 kB) Pennsylvania State University, accessed June 9, 2016 .

[AD-1] Walt Kester: Understand SINAD, ENOB, SNR, THD, THD + N, and SFDR so You Don't Get Lost in the Noise Floor. (pdf; 95 kB) Analog Devices, October 1, 2008, p. 5 , accessed on September 6, 2010 (English).