High frequency OTA-C filters with current and voltage transfer functions based on multiple loop feedback technique

This paper addresses the analysis of three different fourth order low pass filters at cutoff frequency of 10 MHz. The filters are realized using: the inverse follow-the-leader-feedback (IFLF), the leap frog (LF), and cascaded multiple loop feedback (MLF) operational transconductor amplifier-capacitor (OTA-C) filters with voltage and current transfer functions. A CMOS OTA cell proposed in [1] is used to realize the three filters. PSPICE simulations are done using 0.25 ¿m model and supply voltage of ±2.5 V. A comparison between the different filters proved that the current transfer function filters have a lower cutoff frequency error between the theoretical and simulation values, and a lower output referred noise density under 1 K¿ load by a factor of 10^-3. The voltage transfer function has the advantage of having a lower group delay than that of the current transfer function filters.