ABSTRACTThe XOR/XNOR gates are basic building blocks for various digital systems like adders, comparators, multipliers, parity-generator/checker and encryption processor. This paper proposes two realisations each using 2-pass transistors/2-transmission gates and 2-inverters. All the proposed circuits are simulated and compared with existing circuits using Cadence Spectre on both 180 and 90 nm CMOS technology with varying supply rail (from +0.8 V to +1.8 V). The simulation results confirm that the proposed circuits achieve a full rail-to-rail swing, high performance and high noise margin at low voltages. Analytical expressions in support of simulation-results wherever required are included. A typical application in Hamming-code generation is proposed.