In this paper, a novel microring resonator (MRR)-assisted Mach-Zehnderinterferometric (MZI) structure to operate as an electro-optic half adderutilizing the optical switching phenomenon of Si-MRR is proposed. Theproposed device has two Si-MRRs with dual inputs, used in the tandemconfiguration in the lower and upper arms of an MZI structure.An externally controllable optical ‘π’ phase shifter is also incorporatedin one of the arms of the MZI. The carrier-injected forward-biased PINwaveguide structure is incorporated into the ring resonator architectureto achieve the extinction ratio (ER) tunability. For the proposedelectro-optic adder, -1.85 V and +2 V are considered as logic 0 and1, respectively. One of the output terminals will emulate an opticalAND gate providing the carry bit (CB), while the other output terminalwill emulate an optical EX-OR gate offering the sum bit (SB).The proposed device was modeled and simulated using MATLAB. Thesimulation results estimate the simulated static ER of the SB andCB is 27.44 dB and 18.08 dB, respectively. To demonstrate the proposeddevice’s efficacy, two 10 Gb/s PRBS input streams at 1550 nm were used, and the time domain simulation results indicate a successfulelectro-optic half adder suitable for photonic integrated circuits (PICs).