The first part of this thesis described a high-voltage-enabling circuit technique for enhancing the gain precision and linearity of operational amplifier (OpAmp)-based analog circuits. Without resorting from specialized devices, a 2xVDD-enabled recycling folded cascade (RFC) OpAmp optimized in 1V GP 65-nm CMOS achieves ~20-dB higher open-loop DC gain and ~20-dB higher IM3 (in closed loop) than its 1xVDD counterpart under a similar power budget. These joint improvements save the need of a 2nd stage in the OpAmp when high precision and high linearity are the priorities. A voltage-conscious bias scheme and gate-drain-source engineering ensure all devices are consistently operated within the reliability limits. Package effects degrade the performances of high frequency circuits such as wideband low-noise amplifiers (LNAs). The second part of this thesis describes an area-saving technique to improve the performance of a balun-LNA covering the range of 50 MHz to 10 GHz in the presence of package effects. A double active-decoupling technique based on a feedback inverter amplifier is proposed. Optimized in GP 65-nm CMOS, the new technique shows 2.3-dB maximum gain loss compensation, 6.6GHz bandwidth recovery for input matching, and 22-dB maximum noise filtering in both supply rails. The added active circuitry draws 16 mW from a single 1.2-V supply, and the required physical capacitor is reduced to 4 pF.