Low voltage, high speed and high linearity are three different aspects of the analog circuit performance that designers are trying to achieve. In this dissertation, three design projects targeting these different performance optimizations are introduced.;The first work is a design of a low voltage operational amplifier. In this work, a threshold voltage tuning technique for low voltage CMOS analog circuit design is presented. A 750mV operational amplifier using this technique was designed in a 0.5mum 5V CMOS process with Vtp ≈ -0.9V and Vtn ≈ 0.8V. The active area is 560mum x 760mum. It exhibits a 62dB DC gain and consumes 38muW of power. It works with supply voltages from 0.75V to 1V. Compared to its 5V counterpart consuming the same amount of current, it maintains nearly the same gain bandwidth product of 3.7MHz. This op amp is the FIRST strong inversion op amp that works at a supply voltage below the threshold voltage.;The second is a design of a high speed phase-locked loop for data recovery. A new non-sequential linear phase detector is introduced in this work. Most of the existing phase detectors for data recovery are based on state-machines. The performance of these structures deteriorates rapidly at higher frequencies because of the inadequate settling performance of the flip-flop used to form the state machine. The new phase detector has a speed advantage over the state-machine based designs because it is simple and easy to implement in CMOS technology. Using this phase detector, a PLL was designed in a 0.25mum CMOS process with an active area of 400mum x 290mum. Experimental results show it successfully locks to a 2.1Gbit/s pseudo-random data sequence at 2.3V. It is believed that the architecture is the fastest that has been introduced for data recovery applications.;The third work introduces the design of a highly-linear variable gain amplifier. It achieves high linearity with third harmonic distortion better than -60dB Vopp = 1V at 160MHz in a 0.25mum CMOS process. It has a precise gain step of 6.02dB that is controlled digitally. The linearity performance is achieved with a linearized open loop amplifier configuration. Similar performance could only be achieved using feedback configuration before.