[sdiy] any problems using 2N4416A

[patchell]

cacofone wrote:

> Hello,
> How precise do the NPN/PNP jfet transistors have to be to those on the
> parts list of the asm-1? I found a part on radio shack the 2N4416A that
> says low noise, which I think might be better and worth the investment...
> any thoughts? My understanding was a transistor's a transistor, and
> different between pnp and npn and that's it..

    That only applies to BJTs (Bipolar Junction Transistors), FETs are a
completely different story.  All BJT's pretty much work the same, but with FETS,
no two (even of the same type) are identical.  Now granted, this is a bit of an
exageration, but not really too far off the mark.

    Now, the FET you are talking about in the ASM-1 is the discharge transistor in
the oscilator, I assume.  Probably just about any N-JFET will function
there.However, some will function better.  The 2n4391 (I think that is the correct
part number) that is on the schematic is well suited to the job because it has a
fairly low Rdson, and low leakage.  The Drain Source on resistance will affect the
discharge rate.  I am not familiar with the 2n4416, but in general, low noise also
means low resistance, so, you might be OK.

    Another good FET to use is the J111.  I purchased mine from Future-Active
http://www.future-active.com.  They have a terible web site.  I got my J111 for
about 35 cents each.  It is the same chip as the 2n4391, but, you can find them.

>
> Joshua
>
> Pulse 8 / nKode / cacofone [aim:goodtimetribe]
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--
 -Jim
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