This Special Issue is a collection of selected papers presented at the IEEE Asia Pacific Conference of Circuits and Systems (APCCAS) 2019 that was held in Bangkok, Thailand, November 11–14, 2019, and the IEEE International Conference on Electronics, Circuits and Systems (ICECS) 2019 that was held in Genova, Italy, on November 27–29, 2019. As the flagship conferences of the IEEE Circuits and Systems Society (CASS) in IEEE Regions 10 and 8, respectively, these conferences welcome contributions across the themes within the scope of the Society, including analog, digital, and mixed-signal electronics, signal processing, power electronics, communication theory, sensors, circuit theory, and nonlinear circuits and systems. [ABSTRACT FROM AUTHOR]