Re: TO3 & HEATSINK

From: Norm Dresner (ndrez_at_att.net)
Date: 07/28/04 

Date: Wed, 28 Jul 2004 18:05:58 GMT

"exxos" <exxos@home.co.uk> wrote in message
news:4107d861$0$6441$cc9e4d1f@news-text.dial.pipex.com...
> > A little more expensive but good performance in the MJ150xx series of
> power
> > transformers. The complementary pair MJ15003/15004 are higher voltage
> than
> > you need but especially good for high power audio amplifiers. They're
> still
> > TO-3 but there's generally no real problem in routing wires through the
> heat
> > sink if you protect them against rubbing and overheating by installing a
> > gromet in the hole. The 3055 is an old workhorse, best for low
frequency
> > designs like subwoofers.
> >
> > For TO-220 packages, consider a MOSFETs instead of bipolar output
stage --
> > there are some really good medium power units available in this package.
> > Norm
>
>
> The MJ21194 power NPN looks nice, I have already tried some mosfets, They
> seem to sound the same, but when I look at set freqencys on the scope the
> wave is very much distorted, I've been trying this out for the past 2
days,
> ive tried everything I can think of, they just dont seem to work as good
as
> transistors do. I'm all for using mosfets, though I think for my next
> project I'll design a class D amp and use some mosfets for that.
>
> Chris
>
>
MOSFETs require different biasing and somewhat different drivers than
BJTs -- you can't just substitute one for the other. There are a few "good"
books on the subject -- Doug Self and Randy Slone are the latest ones I've
read.

    Norm

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