Performance limitations of stochastic sensors

A stochastic sensor is an integrated sensor/circuit system which provides a digitized sensor output signal as a function of a physical parameter to be sensed. The sensor is an integral part of the positive feedback amplifier which is pulsed N-times through the metastable region. After each clock pulse, a zero or a one is provided at the output. A digital counter counts the number of ones and provides a digital output after N clock pulses. A relative accuracy of 0.4% can be achieved at N=10⁶ clock pulses. This accuracy can be improved by an increase of N. The relative accuracy depends on the number of applied pulses and on the signal amplitude. Temperature changes cause the gain variation of the input-output transfer curve. Clock feedthrough and the resolving time in the positive feedback amplifier impose the limitation on clock speed. An analytical equation of this resolving time during the metastable region is compared with SPICE simulation