Three different chip design topics associated with their respective applications are proposed in this thesis. The first topic is the implementation of an FIFO memory design for 8-to-32 data exchange bus. An FIFO memory architecture is proposed to be utilized in data exchange between processing units which possess non-homogeneous bus widths. Neither arbiter logics nor modules are required in such a design to determine input sequences or output sequences. Hence, the delay is drastically shortened. The second topic is focused on the implementation of an analog front-end of digital cordless headset baseband controller. The integrated analog and digital interface IC provides an interface for analog and digital communication. It converts an analog signal into an 8-bit digital signal, which will be processed by the baseband controller. It also converts an 8-bit digital voice data into an analog voice signal. In addition, a built-in oscillator is included in the design, which provides a global clock signal. The third topic is to carry out an DC/DC converter with a built-in voltage detector. The converter can convert 1.5V input voltage to 2.7V output voltage. A portable system can use only one single battery to power on by this circuit. It also contains a voltage detector to indicate whether the output voltage meets the pre-determined level.