Internet of Things (IoT) devices were projected to be installed in every object surrounding us. Most of the IoT sensing and communication circuits only operate for a very short amount of time and sleep or stand by for a much longer time, as shown in Figure 2.1. This very low-duty-cycle and high peak-to-average power ratio operation feature makes the ultralow standby power a critical specification for the IoT devices to prolong the battery life and recharging cycle. Block diagram of a low-duty-cycle IoT system with DVS. https://s3-euw1-ap-pe-df-pch-content-public-u.s3.eu-west-1.amazonaws.com/9780429507564/a9e9107b-0ee4-43a0-bbab-74e92283bb72/content/fig2_1_C.tif"/>