In this paper, circuit implementation of diamond-shaped type-2 membership function in CMOS technology is presented. Designing of mixed analog/digital circuits provides a flexible configuration as well as the highly accurate performance, where analog circuits are employed to realize required functions, while the programmable units implemented using digital circuits. The current-mode approach is employed owing to the simple circuitry and intuitive configuration to design the circuits. The programmability of the circuit in terms of slopes, upper, and lower modal points enables the expert of the system to create other shapes of type-2 membership functions including rectangular, rhombus, triangular, and trapezoidal. For a particular set of programming parameters of diamond-shaped type-2 membership function, post layout simulation results of the proposed circuit using HSPICE and level 49 parameters (BSIM3v3) in 0.18 m technology, demonstrate an average power consumption of 0.688 mW, maximum propagation delay of 8.7 ns and a relative error as low as 1 %. Furthermore, Monte Carlo analysis is carried out to ensure the robustness of the circuit performance against the process variation.