Seven Steps to Successful Analog-to-Digital Signal Conversion (Noise calculation for proper signal conditioning)

Real-world signals, such as vibration, temperature, pressure, and light, require accurate signal conditioning and signal conversion before further data processing in the digital domain. In order to overcome many challenges in today’s high-precision applications, a well-designed, low-noise analog front-end is needed to get the best SNR. Many systems cannot afford the most expensive parts, nor can they afford the higher power consumption of low-noise parts.

This article presents a methodical approach to the design of a gain block and ADC including an example that supports this approach. Noise calculation and analysis is performed on this circuit when conditioning low-frequency (near dc) signals. It explains these seven steps when designing an analog front end:

  1. Describe the electrical output of the sensor or section preceding the gain block
  2. Calculate the ADC’s requirements
  3. Find the optimal ADC + voltage reference for the signal conversion
  4. Find the maximum gain and define search criteria for the op amp
  5. Find the optimal amplifier and design the gain block
  6. Check the total solution noise against the design target
  7. Run simulation and validate

The article also includes references as well as links to other articles by the author. The article is presented as a pdf file (n registration required). To read the article, click here.

About the author
Reza Moghimi is an applications engineer at Analog Devices in San Jose, CA. He received a BSEE from San Jose State University in 1984 and an MBA in 1990, and has also received a number of on-the-job certificates. He has worked for Raytheon Corporation, Siliconix, Inc., and Precision Monolithics, Inc. (PMI–which was integrated with Analog Devices in 1990). At ADI, he has served in test-, product-, and project-engineering assignments. He has written many articles and design ideas, and has given presentations at technical seminars

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