Single-Supply Operational Amplifier (Op-Amp) is important to the applications on battery-powered equipments whereas MMIC Low Noise Amplifier (LNA) is a type of integrated circuit device used in capturing operating signal in microwave frequency. This paper presents an optimization study of a Single-Supply Op-Amp and a MMIC LNA using Genetic Algorithm (GA). GA is proposed to optimize multiple input variables so as to achieve the required circuit design outputs. In Single-Supply Op-Amp, a single objective GA optimization study is conducted. Based on the single objective circuit design justification, GA is further investigated for its capability to deal with multiple design objectives in 5 GHz MMIC LNA. In this research, the Single-Supply Op-Amp design is synthesized via LTSpice whereas the MMIC LNA design is simulated through Agilent Advanced Design System (ADS). The optimization performance of GA for both single and multi-objective circuit designs is studied and the developed multi-objective GA optimizer is further compared with ADS built-in optimizers of Gradient and Quasi-Newton respectively. From the results, GA is shown to be capable in optimizing both single objective Op-Amp and multi-objective LNA.