NMOS flip-flop sensors: a multipurpose digital-output sensor technique

Abstract

With the current trend toward digital signal processing, a sensor with a digital output has clear advantages over the conventional analogue types. The paper presents a solution using flip-flop as a sensing element. The sensor operates by bringing a flip-flop into the unstable state, large number of cycles. Any imbalance in system, introduced by the parameter to be measured, will change the probability of a ‘one’ ‘zero’ and thus the ratio of ‘ones’ to ‘zeros’ over large number of cycles. Because of the unstable state, this system is highly sensitive to small perturbations. Although both bipolar and NMOS flip-flop sensors have been successfully fabricated, the paper concentrates on NMOS structures.