hmm.. help with mosfets - diyAudio
Go Back   Home > Forums > Amplifiers > Solid State

Solid State Talk all about solid state amplification.

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
Reply
 
Thread Tools Search this Thread
Old 27th August 2002, 03:53 AM   #1
Colt45 is offline Colt45  Serbia
diyAudio Member
 
Join Date: Feb 2002
Location: Canada
Send a message via ICQ to Colt45
Default hmm.. help with mosfets

Ok.. I'll start this off with the fact that I don't know much about solid state at all.. im a tube person..

so anyways, I got some power mosfets. I know they are complimentry pair, but have no idea how to wire that (as I dont know SS).

anywyas here is the pair:
2SD718
2SB688

What i know of them is that they are 120v, 8A, 80w dissipation. I can't find a datasheet though

there is also two gain transistors per channel.
both are:
K1420 (might be 2SK1420)

Anyone want to help me figure out how to wire the output stage? ???

Thanks,
  Reply With Quote
Old 27th August 2002, 06:30 AM   #2
diyAudio Member
 
Join Date: Jul 2002
Location: Naptown
Actually, the 2SB/2SD transistors are BJTs. You can figure out the leads using a Multimeter with with Hfe reading. As these dissipate 80W I'm assuming that they are TO-220 (?) with the most common pinnout looking at the front being: Base, Collector, Emitter.

As for the 2SK1420, This is a MOSFET:

Ultra High Speed Switching
60V 15A 30W in a TO-220 Most common pinnout: Gate, Drain, Source.

As for wiring the OPS, are you working off of a schematic, or are you trying to work out a design of your own? More info is needed as to what you are trying to do.

-D.
  Reply With Quote
Old 27th August 2002, 07:02 AM   #3
Colt45 is offline Colt45  Serbia
diyAudio Member
 
Join Date: Feb 2002
Location: Canada
Send a message via ICQ to Colt45
Oh okay, thanks

I don't have any schematic, but I would like to make a power amp with this (perhaps integrated). I'll probably end up using it for a sub in my room.. but might use it on fullranges as well.

any information as how to wire this would be great

Thanks, Mark

oh yes, they are B-C-E, and TO-220 (well a little bigger than normal to-220's.. i'm not sure what it is called.)

I can probably run it off a preamp, so just power stage is okay for now
  Reply With Quote
Old 27th August 2002, 07:21 AM   #4
diyAudio Member
 
Join Date: Jul 2002
Location: Naptown
Prolly TO-247 or TO-3P. these are bigger than TO-220's and usually can handle up to 300W or so.

The output that you would create from these would then be a Quasicomplimentary Mosfet Design, using the BJT's as driver transistors and the MOSFETs for the Power. There is a small thread on this. It references the Holton N-channel amp, however the OPS is a little more complicated than need be I personally think. This is assuming that you are looking to build a class B or Class AB OPS.

If on the off chance that you want a class A amp from this, then a Zen might be a good choice by just using the MOSFETs. Of course the circuit would need some tweeking to fit these particular MOSFETs.

What were you thinking of for a front end?

-D.
  Reply With Quote
Old 27th August 2002, 07:34 AM   #5
Colt45 is offline Colt45  Serbia
diyAudio Member
 
Join Date: Feb 2002
Location: Canada
Send a message via ICQ to Colt45
I was thinking I might drive it with a tube.. or something like that.

the amp that I pulled these from, the D718 & B688 were used as output, one of each per channel. (touted as 100w per channel, but I assume that was a over-rating)

So I basically wanted to see how to use these as power stage, in complementary (what class is this? I'm used to tubes..)

so for now I'm just trying to get a basic idea of how transistor output works (with a NPN & PNP pair).

thanks.
  Reply With Quote
Old 27th August 2002, 08:08 AM   #6
diyAudio Member
 
Join Date: Jul 2002
Location: Naptown
A Hybred I like that. There seems to be some debate about the quasi-MOSFET thing, but it can be done. Seems that most use Complmentary N and P channel devices for full complimentary as opposed to Quasi. I think that that would be difficult in your situation as I would guess that a P channel compliment doesn't exist for that particular 2SK device. But, if you are good at disecting schematics http://www.passdiy.com/pdf/citation.pdf
would be a good start. This would be a Class B or AB (havn't read the article). Another Idea would be to treat the Mosfets as tubes using transformer coupling setting up a class B PP stage. I've just recently read an old book on transistors that talks about doing this. I'm not familiar with tubes and don't really have audio tranfos laying around to play with, but it might be another idea. I think the "cycletron with n-channel mosfet" thread may cover some of this, but again I havn't read most of it. Hope that helps, it's bed time for me, and keep me posted (I have a bunch of NPN power BJTs that are screaming for something like this).

-D

P.S. I have and old Radio Shack 40W PA amp that uses 2 NPNs and a transformer in the output, can't find a schematic and I use the thing for a monitor so I have yet to tear it down enough to see the exact topology, but maybe soon

What was the Amp that these came out of? Do you have or have you looked for a schematic for it?
  Reply With Quote

Reply


Hide 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
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Where to buy MOSFETs? goodas Solid State 28 16th May 2014 02:40 AM
What mosfets to use? seafire Solid State 18 25th March 2009 10:44 AM
n/p Mosfets vs depletion mod mosfets marcello7x Car Audio 6 4th October 2006 06:01 AM
Why no MOSFETs? Pbassred Solid State 25 1st February 2004 09:06 PM
mosfets, why the big ones jjacks4x Pass Labs 19 19th December 2002 10:19 PM


New To Site? Need Help?

All times are GMT. The time now is 11:43 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2