SINAD from ADC Bits

Formula

Description

This formula gives the theoretical maximum SINAD (signal-to-noise-and-distortion ratio) for an ideal N-bit ADC with a full-scale sine wave input. Each additional bit of resolution adds 6.02 dB of dynamic range. The 1.76 dB offset accounts for the sinusoidal signal being 1.76 dB above the quantization noise for a full-scale input. This represents the absolute best-case performance; real ADCs always achieve less due to thermal noise, clock jitter, nonlinearity, and other imperfections.

Variables

• SINAD — Ideal signal-to-noise-and-distortion ratio (dB)
• N — Number of ADC bits (dimensionless)

Practical Notes

Common ideal SINAD values: 8-bit → 50 dB, 10-bit → 62 dB, 12-bit → 74 dB, 14-bit → 86 dB, 16-bit → 98 dB, 24-bit → 146 dB. In practice, 24-bit ADCs rarely exceed 120 dB SINAD (about 19.7 ENOB) due to thermal noise limitations. Delta-sigma ADCs achieve high SINAD at low frequencies through oversampling and noise shaping.