Low noise, low drift techniques


This presentation has a set of clear, well thought out images describing how chopper techniques can reduce 1/f noise, reduce drift, and even how to cancel the nasty charge injection of FET switches. It shows how modulation can reduce noise in a sensor amplifier system.

link to pdf of Kofi Makinwa\’s presentation, Dynamic Offset Cancellation Techniques

I first learned of Kofi Makinwa’s excellent work through the recent IEEE Solid State Circuits magazine, Winter 2010, Vol. 2, No. 1. He demonstrates a clever accelerometer that uses a small air volume as the ‘proof mass’. The Wheatstone bridge has been around a long time, but it’s clear it can be taught some new tricks. This is the first I’ve heard of a ‘nested chopper’ architecture. Great stuff. Check out Makinwa’s other publications at the IEEE.

I’ve spent some time trying to squeeze good data from MEMS sensors, and I know how difficult it can be. These articles show why adding some switches and circuit complexity can really pay off. And it’s only CMOS and FETs, so we get ‘em for free from Moore’s law, right?

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