Two-stage unbuffered CFOA based non-inverting resistive-feedback amplifier: a study based on the description of the operational transconductance conveyor (OTC)

Abstract

A study of the non-inverting amplifier based on a two stages CMOS unbuffered current-feedbackamplifier (UCFOA) is proposed in this paper. Using a small-signal equivalent circuit (macro-model) of the non-inverting amplifier, a theoretical explanation of the closed loop gain is given. The opamp phase margin and its bandwidth have been estimated from the quality factor Q of resonance and using a novel description of the UCFOA input stage called Operational Transconductance Conveyor (OTC). The OTC description can be viewed as an extension of type II second generation current conveyors. Based on the fundamental parameters of the proposed OTC, a theoretical approach given in this paper explains how to evaluate precisely the value of the UCFOA compensation capacitance. PSPICE was used to simulate both the theoretical macro-model and the CMOS configuration from a 0.35m typical BSIM3V3 transistor models.

CMOS voltage and current feedback opamps: a comparison between two similar topologies

“…In a similar way, the Operational Transconductance Conveyor (OTC) as input stage in series with a VB as output stage permits to describe the CFOA; the high impedance node Z is now the node between the OTC output and VB input. The OTC description [2] is also useful because it allows the description of each type of Current Feedback Operational Amplifier (CFOA) input stages [2]. Several names and acronyms are used to describe opamp topologies.…”