An Exponential Current Generator

A current getlerator has been constructed from two operational amplifiers and a thermostated twin transistor. The current is an exponential function (5) of a controlling voltage. At currents greater than 100 μA, the transistor exhibited a resistive effect, for which it was possible to compensate for internally. The generator was tested over the current range 30 nA-15 mA and was found to perform almost ideally, with a slope of 1.008 of the theoretical and a standard deviation of 0.3 perceht. Some preliminary measurements have shown the generator to be useful down to 10 pA. The use of the generator for electrochemical kinetic measurements is described.