Patent US 4,338,527

A voltage-current conversion circuit comprises an input terminal, a conversion terminal, an output terminal, first and second emitter-coupled transistors having their bases respectively connected to the input terminal receiving an input signal and the conversion terminal, a current mirror load circuit connected to collectors of the first and second transistors, a constant current source connected to emitters of the first and second transistors, and an output transistor having its base connected to the collector of the second transistor and its emitter to the conversion terminal. When the collector of the output transistor is connected to the output terminal and an impedance element is connected to the conversion terminal, a current is provided at the output and conversion terminals which is obtained by dividing an input signal voltage applied to the input terminal with an impedance value of the impedance element. The voltage-current conversion circuit serves as a negative current conveyor. When the collector of the output transistor is connected to an input terminal of a current mirror having its output terminal connected to the output terminal of the conversion circuit, the converting circuit serves as a positive current conveyor. Proper combinations of the positive and/or negative current conveyors provide various analog computation circuits.