Chapter 10 - Voltage and Current Feedback Op Amp Comparison

Abstract

This chapter explores the comparison between voltage and current feedback op Amp. The name operational amplifier was given to voltage feedback amplifiers (VFA) when they were the only op amps in existence. These new amplifiers could be programmed with external components to perform various math operations on a signal, so they were nicknamed op amps. Current feedback amplifiers (CFA) have been around approximately 20 years. Two factors limit the popularity of CFAs, their application difficulty and lack of precision. The VFA is a familiar component, and several variations of internally compensated VFAs can be used with little application work. VFA bandwidth is limited, so it cannot function as well at high signal frequencies as the CFA. For now, the signal frequency and precision separates the applications of the twoop amp configurations. The VFA has other redeeming virtues, such as excellent precision, that makes it the desirable amplifier in low frequency applications. Many functions other than signal amplification are accomplished at low frequencies, and functions like level shifting a signal require precision. Fortunately, precision is not required in most high frequency applications, where amplification or filtering of a signal is predominant, so CFAs are suitable to high frequency applications. The lack of precision coupled with the application difficulties prevents the CFA from replacing the VFA.