A digital microsensor with auto-zero offset compensation

A stochastic digitizer utilizing two inverters in a positive feedback loop is used to convert a small analog sensor signal into a digital sensor signal. An automatic offset compensation method using floating gate MOSFETs is used to overcome the offset error in the stochastic digitizer. The operating principle of the stochastic digitizer is described, and its input-output transfer curve is given. The offset errors which cause problems in the signal measurement of the stochastic digitizer are discussed. A programmable inverter using floating gate n-channel MOSFET is demonstrated. An auto-zero offset compensation technique is presented which eliminates the offset error of the stochastic digitizer circuit and of the sensor