This dissertation investigates the operation of the regenerative amplifier (RA) in the linear and nonlinear regimes, especially regarding the noise performance, and several integrated applications in which it can be extremely helpful to enhance system performance. Chapter 2 analyzes an interesting phenomenon associated with an RA operating in the nonlinear regime, that exhibits a suppression of the in-band noise, resulting in an improvement on the output carrier-to-noise (CNR) ratio. A promising application of the phenomenon in electromagnetic tomography is also discussed. Chapter 3 delves into an application of a dual RA architecture to demodulate an OOK signal non-coherently, which is a state-of-the-art 2.4-GHz receiver that has an excellent sensitivity of -101 dBm and an ultra-low power of 112 μW with an impressive signal-to-interference ratio (SIR) of -28 dB at a 3-MHz offset. Chapter 4 presents yet another state-of-the-art, ultra-low power receiver employing dual RAs that is compatible with Bluetooth Low Energy (BLE) and WiFi, that achieves an excellent sensitivity of -80 dBm for 16QAM, while the active power consumption is only 30 μW and the energy efficiency is the highest compared to prior works in the literature. The receiver can be deployed on smart wearable devices to communicate directly with a smartphone or a WiFi access point to significantly improve battery life while still retaining a high data throughput.