Seyed Vahid Feizbakhsh - is with the Electrical Engineering Department, Mahabad Branch, Islamic Azad University, Mahabad ۵۹۱۳۹۳۳۱۳۷, Iran
Ghader Yosefi - is with the Electrical Engineering Department, Mahabad Branch, Islamic Azad University, Mahabad ۵۹۱۳۹۳۳۱۳۷, Iran

In this paper, we re-do simulation of a recycling folded cascode (RFC) op-amp which was published by Rida S. Assaad and et all, in IEEE Journal of Solid-State Circuits. The authors presented and simulated the RFC circuit to obtain DC gain using AC analysis only. They achieved to the results that with increasing the factor of k (the ratio of cross couple transistors in RFC circuit) the DC gain can be improved. But, we criticize their work scientifically and present a contrary result. We calculate and analyze the transconductance and output resistance of RFC op–amp using both DC and AC analysis. So we propose new results and prove this fact that with increasing k (1.5

RFC Op-Amp, CMOS, DC gain, DC and AC analysis