Mosfet

Willow

What is it and how does it differ.

gatemplin

This is what I remember. Mosfet is metallic oxide silicon field effect transistor. They differ from normal emitter base collector transistors because they aren't controlled by current. They use an electric field to change the width of a channel. I think I remember the reason FETs are used is that they run much cooler, consume less power and maybe switch faster.

HBombToo

I recall their bias voltage is much less than the typically doped silica. As gate mentioned the channel is opened or closed by the bias voltage and as we decrease the voltage requirement the speed and accuracy increases.

HBomb

unc2701

From the Adcom webpage:


My amplifier seems to run hot. Is this a problem?

Probably not. Most Adcom amplifiers use output devices called "MOSFETs" (which stands for metal oxide semiconductor field effect transistor, if you're curious). We've chosen these devices for their superb 'musicality'. They do, however, run hotter than more conventional bipolar transistors. We have designed our amplifiers with large 'heat sinks' made up of aluminum fins that dissipate excess transistor heat into the air. Just make sure you provide adequate room for ventilation as opposed to stacking other equipment directly on top of your amplifier.


What's the difference between your old amps and your new ones?

Well, the biggest difference goes back to MOSFETs again. Most of our newer "4 number" amplifiers (i.e. the GFA-5802) use MOSFETs while all our older "3 number" amplifiers (i.e. the GFA-555), used bipolars.




So, are bipolar amplifiers bad?

Actually bipolars have some advantages. As noted above, they produce less heat for a given power output. This makes them suitable for more compact components or for multi-channel, home theater amplifiers. As such, we have chosen to use them in our custom oriented amplifiers, the GFA-5002 and the GFA-5006, where size can be at a premium, and in our multi-channel, home theater amplifiers, the GFA-7500, GFA-7400 and GFA-7300.

Bipolars can have a very detailed, up front sound quality, and with our 2 decades of experience in getting the most out of these devices, we think you'll find that the bipolar's inherent immediacy is nicely tempered with circuit touches that let you hear a rare level of musical integrity.