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dsPIC33A 12-bit 40MSPS Analog-to-Digital Converter (ADC) Deep Dive

Signal-to Noise Ratio and Effective Number of Bits (ENOB)

Last modified by Microchip on 2026/03/31 13:06
   Input Model - Sampling Time  Signal to Noise Ratio - Oversampling   

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ACD SNR

Input Noise and Analog-to-Digital Converter (ADC) Performance

  • The Signal-to-Noise Ratio (SNR) is a key factor in Analog-to- Digital Conversion (ADC) performance.
  • The SNR is calculated by integrating all noise over the full Nyquist bandwidth. The noise contributions include ref. buffer noise, ADC quantization noise, thermal noise, flicker noise, and ADC aperture jitter.
  • For the dsPIC33A ADC, it supports a typical SNR of 65 dB with a typical Effective Number of Bits (ENOB) of 10.5b.

ENOB

  • ENOB is a key performance metric for ADCs.
  • ENOB represents the actual resolution of an ADC after accounting for all sources of error, such as noise, distortion, and non-linearity.
  • ENOB provides a realistic measure of ADC quality.
  • It helps designers compare ADCs and understand how much usable resolution is available in practical applications.
  • ENOB tells you how many bits of an ADC’s output are truly reliable, considering all imperfections in the conversion process.