This thesis includes two topics. The first topic is a low power design of 8-bit ANT-based pipelining CLA. The second one is a small digital to analog converter (DAC) used in an implantable neural stimulator. An ANT-based low-power 8-bit pipelining carry-lookahead adder (CLA) using two-phase all-N-transistor (ANT) blocks which are arranged in a PLA design style with power-aware pipelining is presented. The pull-up charging and pull-down discharging of the transistor arrays of the PLA are accelerated by two feedback MOS transistors between the evaluation NMOS blocks and the outputs. Both the added power-aware clock control circuit and clock generation circuit detecting data transition take advantage of shutting down the processing stages given identical inputs in two consecutive operations by keeping high clock level. The design keeps the advantage of high speed while having the effect of low power dissipation. The implantable neural stimulator assists patients to reconstruct transmission paths of neural signals by current stimulation. The proposed small DAC not only decreases the chip area and power dissipation by reducing transistor count, but also improves the linearity with higher current output performance. All of measured performances of the proposed DAC make the chip worthy of being implemented in a field application.