Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Solid State Talk all about solid state amplification.

Mosfet versus bipolair
Mosfet versus bipolair
Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Thread Tools Search this Thread
Old 20th November 2001, 09:07 AM   #1
HaaiFaai is offline HaaiFaai
diyAudio Member
Join Date: Nov 2001
Hello diy-ers

Browsing through the several webpages on the world wide web.
I saw many amplifier design concepts using Mosfet and bipolair.
What I found most of the time is that the designers using bipolair devices such as(the ring emitter) transistors from
various brands as Sanken/Motorola/Toshiba etc is that
they are suspicious in using Mosfets at all in their designs,telling that Mosfets are unreliable/more non lineair/prone to oscillation and therefor more useful in switching applications.
The designers of Mosfet amplifiers are blaming the bipolair of being hard to get them working with high base current and thermal unstable etc.
Who can give clarification and has experience on both devices?

[Edited by HaaiFaai on 11-20-2001 at 04:34 AM]
  Reply With Quote
Old 20th November 2001, 10:00 AM   #2
AudioFreak is offline AudioFreak  Australia
Warp Engineer
On Holiday
AudioFreak's Avatar
Join Date: Oct 2001
Location: Queensland, Australia
Mosfet versus bipolair
both are partially true........

if the amps is highly efficient (ie. it doesnt produce much heat and therefore has a low bias current) bipolar transistors are usually better and more linear but you will need to protect them from secondary breakdown ........

if the amps is not so efficient (ie. it produces quite alot more heat and therefore has a somewhat higher bias current) mosfets are usually better and more linear and you will not need to protect them from secondary breakdown ........

mosfets get a bad wrap when people try to use them with very little bias current because in this situation they sound dreadful and can suffer from thermal creep......

when the bias current is measured in amps, mosfets are brilliant which is why in almost all the (solid state) highly biased class AB amps and the true class A amps use mosfets at the output ......

in short, each device has its place ..... neither is perfect ..... but if you dont care about how much power you waste, dont mind your amp doubling as a space heater and want the best quality sound possible use mosfets with as much bias current thru the output devices as you can afford.
  Reply With Quote
Old 20th November 2001, 06:22 PM   #3
Nelson Pass is offline Nelson Pass  United States
The one and only
Nelson Pass's Avatar
Join Date: Mar 2001
Mosfet versus bipolair
AudioFreak pretty much nails it.

Myself, I've made good money designing both, for the
last 30 years, but I personally prefer Mosfet in
Class A mode.
  Reply With Quote
Old 22nd November 2001, 12:24 PM   #4
HaaiFaai is offline HaaiFaai
diyAudio Member
Join Date: Nov 2001
Default Thanks! another question..


I recently was browsing on the Hafler website and I saw that they are using (amongst others as well) a different kind of set up with grounded Mosfets (and QSC grounded transistors)in the output stage
Is this the way to go if you want to reduce the amount of active devices in the chain? Or is this only for the PA market?
I saw diagrams of Hafler,Chevin,QSC and others..

  Reply With Quote


Mosfet versus bipolairHide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
T-Amp versus Gainclone jacklelad Class D 18 15th September 2008 01:49 AM
ZRT 2 way versus 2.5 way s7horton Multi-Way 5 13th August 2008 06:23 PM
TPP versus PSE. GeirW Tubes / Valves 11 27th November 2004 08:55 AM
Active Sub versus Car sub massive_cranium Subwoofers 0 26th September 2003 02:18 PM
2.5 way versus 3 way Mos Fetish Multi-Way 1 6th April 2003 06:57 AM

New To Site? Need Help?

All times are GMT. The time now is 08:52 AM.

Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 16.67%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Copyright ©1999-2018 diyAudio