[sdiy] newbie alert - transistor question

[Cynthia Webster]

on 1/4/05 6:02 PM, groovyshaman at groovyshaman at snet.net wrote:

> Hopefully this isn't too brutal of a common knowledge question!

Hi George!

> Ok, I'm in the process of ordering some 2N2222A transistors for a few
> projects I working on (one of them is a Blacet dark star - finally).  And
> so I have come upon a strange question: is there any advantage to buying
> them in TO-18 cans over TO-92 plastic?  Why do they still make cans?
> Should I even be concerned with this?  I've been reading lies.. err..
> datasheets, googling, etc. but other than the cans handling slightly
> higher junction temps, I just don't see the benefit in spending 30 bucks
> more for 100 pieces O' TO-18.  (Besides, if they're anywhere near 150C
> I've likely got a much bigger problem!)  I appreciate any thoughts,
> strange or otherwise! :)

There are a few of us who think that the metal can versions "sound better"
in certain applications.  It was my experience when switching between
metal can and plastic bodied 2N2222s while building the Steiner Filters.

I prefer the metal, but it is a very subtle improvement.
As far as ~why~ well... the slew rate of the plastic ones are faster
because the metal ones have to drag around the capacitance of the
metal can itself, and thus the plastic body transistors are best suited
for higher speed applications.

It most likely will not matter much in our applications,
but with weaker transistors than the mighty 2N2222, the metal can
capacitance phenomenon may be even more of a boat anchor?
> 
> PS: I've lurked (mostly) on this list now for over three years and it
> continues to amaze me how much knowledge there is here, and how much I
> have to learn.  

Me too, always so much to learn around here
(Thanks Everybody!!)

Cynthia

> Most of this knowledge comes from rubber-meets-the-road
> practical experience which is nearly impossible to find elsewhere, and it
> is invaluable.  When you share your experiences, it is greatly
> appreciated!  Most of my experience to this point is building kits (MOTM,
> Oakley, etc.), a simple FET preamp (for hooking a cello to my modular),
> and a 76477 noisemaker I built 20 years ago.  Although I am totally self
> taught in this field (a software engineer by trade), a crazy long term
> goal I have is that at some point I can design and build a few interesting
> synth modules and share them on this list.  I plan to actually go though
> the process, screw up, and learn.  I think this is the only way to do it.
> I just hope you all won't mind if I ask for assistance (or an oddball
> question) from time to time.
> 
> Cheers,
> George
>