Current Conveyors
Current Conveyors
First generation current conveyor (CCI) was introduced as an active element already in 1968 by authors K.C. Smith and A. Sedra [1]. Since then, the active element has undergone a long evolution. Until now, three generations of current conveyor and universal current conveyor (UCC) [2] were presented. UCC provides implementation of all previous generations and types of current conveyors.
In general, current conveyors can be presented as functional elements, which have variously defined relationships between input and output currents (current conveying) and differently and independently defined relationships between input and output voltages. The real current conveyors have for example better frequency properties than classical operational amplifier. Current conveyors belong to modern building blocks that enable to realize circuits with improved electrical properties. Electronic circuits with current conveyors allow to extend frequency range of processed signals, improve noise resistance and dynamic of circuits. Last but not least they are also able to operate at lower voltage and power sampling, which is currently very important factor especially for circuits for mobile devices with battery power.
Schematic symbol of classical three-port current conveyor is shown in Fig. 1a. Own function of current conveyor can be described very simply on the basis of the block diagram shown on Fig. 1b. Diagram uses to describe the voltage (VF) and current (CF) follower.
Fig. 1: a) Schematic symbol b) Block diagram of current conveyor
Terminal Y is the voltage input, terminal X is the current input. Terminal Z is current output with positive or negative transfer of current from the terminal X.
References
[1] Smith K.C., Sedra A., The current conveyor: a new circuit building block, IEEE Proceedings of the CAS, 1968.
[2] Jeřábek J., Vrba K., Vybrané vlastnosti univerzálního proudového konvejoru, ukázka návrhu aplikace, http://www.elektrorevue.cz , Brno, 2005.
