A Linear Current Regulator

Conventional vacuum-tube current regulators are effective in maintaining a current at a predetermined value, accounting for their widespread use in the familiar electronically regulated power supplies. In some applications, however, it is desirable to have the controlled current respond literally (or in some other specified fashion) to changes in some mechanical controlling device; and the ordinary circuits do not satisfy this condition, since their linearity depends upon that of an associated dc amplifier. To be sure, any desired approximation to linearity can be obtained by increasing the gain of this amplifier, but for many purposes a sufficiently linear regulator of adequate stability becomes unnecessarily complex. The simple circuit described here is novel in that its linearity depends upon that of no element except a single helical potentiometer, which is inexpensively available to linearity tolerances of 0.1 percent or better