Lfa-150: A Fast Power Amplifier (Part 1)

20 EE November 1988 LFA-150: A FAST POWER AMPLIFIER (PART 1) from a basic idea by A. Schmeets This first of a two-part article describes the design of a power amplifier that makes use of very fast ring-emitter transistors and delivers up to 150 watts into 8 ohms. A feature of the design is the low negative-feedback factor. Although commercial high-quality audio power amplifiers have made use of multiple-emitter and ring-emitter tran- sistors for some time, these devices have not been easily obtainable for private purposes. That situation has changed, fortunately, and a number of importers can now supply them on a small- quantity basis. Multiple-emitter transistors consist of a number of identical transistors connec- ted in parallel on one chip. The ring- emitter transistor is a power transistor with a special chip structure for the base, collector and emitter regions. These transistors are the fastest and most linear devices for use in audio power amplifiers. High-quality audio po...