This book presents innovative strategies to implement ultra-low voltage (ULV) and low power active circuits used in low energy RF receivers. The authors demonstrate that the use of single-stage amplifiers with the input negative transconductance compensation is a key strategy to allow the operation at low voltage levels with reduced power dissipation. Also, some design methodologies, based on the CMOS transistor operation point, are analyzed and a powerful design methodology is described for this kind of circuit. Readers will be enabled to implement the techniques described to design communication circuits with low power dissipation, useful in a variety of applications, including IoT/IoE devices.