The current conveyor: history and progress

To create a better voltage-to-current converter, it seemed natural to use another junction, that of a matched pnp transistor connected as a diode, to compensate for the V_EB of the current-source transistor. However, for this compensation to be effective it was necessary to arrange that the current in the additional pnp transistor track that in the current-source transistor, which was supposed to vary over a number of decades. A five-transistor circuit that provides a nice solution to the problem of creating a precise voltage-to-current converter is proposed. It was incorporated into the circuit for a controlled oscillator with good results. The circuit and its applications are described