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

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.