This monograph presents techniques to improve the performance of linear integrated circuits (IC) in CMOS at high frequencies. Those circuits are primarily used in radio-frequency (RF) front-ends of wireless communication systems, such as low noise amplifiers (LNA) and mixers in a receiver and power amplifiers (PA) in a transmitter. A novel linearization technique is presented. With a small trade-off of gain and power consumption this technique can improve the linearity of the majority of circuits by tens of dB. Particularly, for modern CMOS processes, most of which has device matching better than 1%, the distortion can be compressed by up to 40 dB at the output. A prototype LNA has been fabricated in a 0.25um CMOS process, with a measured +18 dBm IIP3. This technique improves the dynamic range of a receiver RF front-end by 12 dB. A new class of power amplifier (parallel class A&B) is also presented to extend the linear operation range and save the DC power consumption. It has been shown by both simulations and measurements that the new PA doubles the maximum output power and reduces the DC power consumption by up to 50%.