Abstract The thesis comprises two different IC design projects, which are briefly introduced as follows. The first part is the NIC (Network Interface Controller) design. The NIC implements all of the Media Access Control (MAC) layer functions for transmission and reception of packets in accordance with the IEEE 802.3 standard. The design is compatible with CSMA/CD type Local Area Network, i.e, 100/10 Mbps Ethernet. The second part is a post-amplifier for a 16Mbps infrared transceiver module. We presents a design of the post-amplifier to convert the pre-amplifier output into digital pulses such that the baseband digital codec can further translate the pulses into the format of IrDA protocols. The design of the amplifier is aimed at the VFIR (very fast infrared) which is supposed to provide a 16 Mbps data transmission rate. The circuit design is carried out by TSMC 0.35 um 1P4M CMOS technology. The simulations results of the design meet the required specification of IrDA VFIR.