Inductor realization with RC elements

The circuit for realizing an inductor with two transistors and RC elements, reported recently by Patranabis, is shown to be a simple transistorized version of a previously published circuit of Rao and Venkateswaran, using two differential input operational amplifiers-each connected as a unity gain amplifier. It is also demonstrated that the transistor RC circuit has severe limitations with respect to Q and its sensitivity.