Digital offset rejection mechanism

Abstract

This disclosure describes circuitry to improve the cancellation of the input-referred offset in the opamp of a sensor front end by implementing a feedback path around the opamp in the digital domain. This implementation uses an A/D converter, a digital integrator and a D/A converter. The A/D converter can be a 1-bit converter constructed with a comparator. The performance of the comparator can be improved by using a chopping technique. The integrator can be initialized upon power-up to a state from a previous measurement, dramatically reducing the convergence time. The gain of the feedback path can be adjusted, which lowers or raises a low frequency pole. Lowering the gain lowers the pole frequency and improves the low frequency response of the transducer path. The low frequency pole can be set track the slowly varying opamp offset.

Dependencies are inferred from the claim text.