Comments on "Improved Accuracy Pseudo-Exponential Function Generator With Applications in Analog Signal Processing"

Recently a new CMOS current-mode pseudo-exponential function generator circuit was reported by Popa. The entire analysis and exponential function generator circuit, given in Popa's paper, is based on a current-squaring circuit module. In this comment paper we show that the current-squarer circuit, presented in Popa's paper, does not work as a current squarer. Consequently the pseudo-exponential generator also does not work as described in Popa's paper. We present a detailed mathematical analysis in this paper to derive its actual operation. Simulation results of the circuit module using Mentor Graphics custom IC design tool set, in a TSMC 0.18-μm CMOS process, are also shown in this paper. Simulation results match the behavior predicted by mathematical analysis.