This book aims to design CMOS programmable current mode building blocks and field programmable analog arrays (FPAAs). A detailed study of programmable current operational trans-conductance amplifiers (OTA) is presented. Five proposed fully differential digitally programmable OTAs based on using fully differential CCs and current division networks are presented. Two of the proposed OTAs are realized using CMOS current division networks while the other three OTAs are realized using MOS current division networks. The proposed OTAs CMOS designs and simulations are presented in details. All the proposed OTAs are digitally controlled using three-bit code word. A multi-standard baseband receiver chain suitable for Bluetooth/UMTS/DVB-H/WLAN standards is presented as an application using the proposed OTA. Three novel FPAA architectures are given based on the proposed OTAs. The FPAAs have hexagonal layout. Two of the proposed FPAA architectures are realized using fully differential CC and CMOS current division network based programmable OTA. The third FPAA architecture is realized using fully differential CCs and MOS ladder current division network based programmable OTA.