An approach to model high-frequency distortion in negative-feedback amplifiers

• Published in: International journal of circuit theory and applications Vol. 36; no. 1; pp. 3 - 18
• Main Authors: Cannizzaro, S. O., Palumbo, G., Pennisi, S.
• Format: Journal Article
• Language: English
• Published: Chichester, UK John Wiley & Sons, Ltd 01.01.2008
• Subjects: amplifiers; analog circuits; circuit analysis; feedback; harmonic distortion; nonlinear distortion
• ISSN: 0098-9886; 1097-007X
• DOI: 10.1002/cta.393

In this paper, we present an analytical approach to study the harmonic distortion in the frequency domain of operational amplifiers (opamps) embedded in a nonlinear feedback network. The analysis is based on a frequency‐domain block scheme that models the opamp with one block and the feedback network with two blocks, but it is demonstrated that only one feedback block needs to be characterized for the two basic inverting and non‐inverting configurations. The obtained closed‐form expressions extend our understanding of nonlinear frequency behaviour in feedback opamp circuits. Indeed, they give the contribution of each network component to the output distortion. As an instructive example, we analysed second‐ and third‐order harmonic distortion of an active‐RC inverting lossy integrator having all the components nonlinear. The accuracy of the proposed method is confirmed by comparison with computer simulations at transistor level. Copyright © 2006 John Wiley & Sons, Ltd.