New possibilities and trends in circuit design for analog signal processing

Operational amplifiers are well-known and mostly used building blocks for analog circuit design. However, due to their limited performance, researchers look for better alternatives and other active blocks. As a result, there is significant amount of past and on-going research about new current-mode active building blocks such as operational transconductance amplifiers (OTA), second generation current conveyors (CCII), current-feedback op-amps (CFOA), four terminal floating nullors (FTFN), differential voltage current conveyor (DVCC), differential difference current conveyor (DDCC), third-generation current-conveyor (CCIII), dual X current conveyors (DXCCII), current controlled current conveyors (CCCII), current differencing trans conductance amplifiers (CDTA) etc. Using these new active elements for analog design and implementing them in CMOS technology designers have acquired new possibilities to solve classic opamp based problems such as bandwidth, slew-rate etc. Moreover, active-only and MOS-only topologies provide further solutions for analog circuit design. Additionally, usage of FGMOS transistors in analog circuits is an alternative approach whose efficiency has been shown recently. This paper discusses these new possibilities in analog circuit design including applications on communication, measurement and RF systems, combining the main features for the circuit design with actual circuit realizations and demonstrating several performance limitations on chosen circuit examples.