An approach to test the open-loop parameters of feedback amplifiers

Author

Giustolisi, G. ; Palumbo, G.

Author_Institution

Dipt. Elettrico, Elettronico e Sistemistico, Catania Univ., Italy

Volume

49

Issue

1

fYear

2002

fDate

1/1/2002 12:00:00 AM

Firstpage

70

Lastpage

75

Abstract

A novel method for determining open-loop parameters, such as unity-gain frequency and phase margin, in feedback amplifiers is given. It is based on relations between open-loop and closed-loop configurations and is very useful for evaluating the above parameters in a unity-gain amplifier from a simple measure of its closed-loop 3 dB cutoff frequency and the respective phase for a given feedback factor β. The approach is validated by simulations of an ideal amplifier and of a real OTA. Moreover, measures carried out for a μA-741 operational amplifier show a percentage error between real and calculated values lower than 2%

Keywords

closed loop systems; feedback amplifiers; frequency measurement; operational amplifiers; phase measurement; pole assignment; transfer functions; OTA; closed-loop configurations; closed-loop cutoff frequency; feedback amplifiers; frequency measurement; ideal amplifier; open-loop configurations; open-loop parameters; operational amplifier; phase measurement; real poles; transfer function; unity-gain frequency margin; unity-gain phase margin; Cutoff frequency; Feedback amplifiers; Frequency measurement; Gain measurement; Noise level; Operational amplifiers; Phase measurement; Power amplifiers; Power supplies; Testing;

fLanguage

English

Journal_Title

Circuits and Systems I: Fundamental Theory and Applications, IEEE Transactions on

Publisher

ieee

ISSN

1057-7122

Type

jour

DOI

10.1109/81.974877

Filename

974877