Feedforward compensation of the amplifier output stage for improved stability with capacitive loads

Author

Leach, W. Marshall, Jr.

Author_Institution

Georgia Inst. of Technol., Atlanta, GA, USA

Volume

34

Issue

2

fYear

1988

fDate

5/1/1988 12:00:00 AM

Firstpage

334

Lastpage

338

Abstract

It is pointed out that the stability margin of an audio power amplifier is reduced by a pole in the loop-gain transfer function caused by shunt capacitance in the loudspeaker load. The problem is most severe in amplifiers with output stages that have a high output impedance before feedback. Because MOSFET devices can have an output impedance that is much higher than BJT (bipolar junction transistor) devices, amplifiers with MOSFET output stages are particularly susceptible to load-induced oscillations. A feedforward frequency compensation technique is described that bypasses the pole in the output stage caused by the load capacitance for improved stability of the amplifier

Keywords

audio-frequency amplifiers; insulated gate field effect transistors; load (electric); power amplifiers; stability; MOSFET devices; amplifier output stage; amplifier stability; audio power amplifier; bipolar junction transistor; capacitive loads; feedforward frequency compensation; high output impedance; load-induced oscillations; loop-gain transfer function; loudspeaker load; pole; shunt capacitance; stability margin; Capacitance; Circuits; Frequency; Impedance; Inductors; Loudspeakers; Output feedback; Shunt (electrical); Stability; Transfer functions;

fLanguage

English

Journal_Title

Consumer Electronics, IEEE Transactions on

Publisher

ieee

ISSN

0098-3063

Type

jour

DOI

10.1109/30.2950

Filename

2950