BiCMOS circuits which can realise the different mathematical operations within a fuzzy system are presented in this paper. To maximise the operating speed of these circuits and increase the packing density, an analog approach is adopted throughout. The initial focus is on the design of circuits to implement fuzzification and intersection. The remainder of the paper focuses on the hardware implementation of implication and defuzzification, thus completing the fuzzy cell library. A major objective of this work is to maintain a design strategy which yields simple circuits so as to minimise cell density. Therefore, the circuits presented are relatively simple but effective with regard to the mathematical functions that they are required to generate within the cell. For example, fuzzification is achieved using the current spike derived from a CMOS inverter during switching. Both intersection and implication are realised using a single MOS transistor operating in the triode region. The remaining circuitry consists mainly of an operational amplifier in the summing mode to realise the function of defuzzification. The complete fuzzy system is simulated and a transfer characteristic is presented and discussed.