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Digital Converter Dynamic Range

Digital converters are quoted as being 16bit, 20bit, 24bit etc. This is really what number of bits they accept as an input signal rather than the number of bits they are working with internally to do the conversion. The table below shows the signal levels for various bit depths. It is interesting to note that quoted dynamic range for ADCs and DACs seems to fall in line with reduced bit depths. e.g. the ADAV801 ADC has a dynamic range of 102dB which suggests that it is only a 17bit device. Where as the AD1955 and CS5381 are quoted as 120dB - 20bit devices? The data sheets can tell you more than you might think but it is well hidden.

Decibels Ratio from ref Resolution dBu - RMS V dBu - Pk/Pk V dBV - RMS V dBV - Pk/Pk V Consumer RMS
20dB 1000%   7.75 22.0 10 28.3  
10dB 316%   2.5 6.93 3.16 8.9  
6dB 200%   1.55 4.37 2.0 5.6  
3dB 141%   1.1 3.1 1.4 4.0  
0dB 100%   775mV 2.2 1 2.8 2.0
-10dB 32%   250mV 690mV 320mV 890mV 640mV
-20dB 10%   77.5mV 220mV 100mV 280mV 200mV
-40dB 1%   7.75mV 22mV 10mV 28.3mV 20mV
-48dB 0.39% 8bits 3.1mV 8.7mV 4mV 11mV 8mV
-54dB 0.195% 9bits 1.5mV 4.4mV 2mV 5.6mV 4mV
-60dB 0.1% 10bits 780uV 2.2mV 1mV 2.80mV 2mV
-66dB 0.049% 11bits 380uV 1.1mV 500uV 1.4mV 1mV
-72dB 0.024% 12bits 190uV 540uV 240uV 700uV 500uV
-78dB 0.012% 13bits 95uV 270uV 120uV 350uV 240uV
-80dB 0.01%   78uV 219uV 100uV 280uV 200uV
-84dB 0.0061% 14bits 47uV 130uV 61uV 170uV 120uV
-90dB 0.0031% 15bits 24uV 67uV 31uV 86uV 61uV
-96dB 0.0015% 16bits 12uV 33uV 15uV 43uV 31uV
-100dB 0.001%   7.8uV 21.9uV 10uV 28uV 20uV
-102dB 0.00076% 17bits 5.9uV 17uV 7.6uV 22uV 15uV
-108dB 0.00038% 18bits 3uV 8.3uV 3.8uV 11uV 7.6uV
-114dB 0.00019% 19bits 1.5uV 4.2uV 1.9uV 5.4uV 3.8uV
-120dB 0.0001% 20bits 740pV 2.1nV 950pV 2.7uV 1.9uV
-126dB 0.000048% 21bits 370pV 1.0nV 480pV 1.3uV 950pV
-132dB 0.000024% 22bits 180pV 520pV 240pV 670pV 480pV
-138dB 0.000012% 23bits 92pV 260pV 120pV 340pV 240pV
-140dB 0.00001%   78pV 220pV 100pV 280pV 200pV
-144dB 0.000006% 24bits 46pV 130pV 60pV 170pV 120pV
-193dB 0.00000002% 32bits 180fV 510fV 230fV 660fV 470fV
Name Ratio from ref Resolution dBu - RMS V dBu - Pk/Pk V dBV - RMS V dBV - Pk/Pk V Consumer RMS