From: bqt at softjar.se
---snip---
> Jeri Ellsworth built some FETs and simple gates at
home -- but she said
> it took two years to figure out how to make it work, and she needed some
> equipment (like vacuum chambers) that few people have at home. It was
> far from simple.
>
---snip---
I purposely picked bipolar since they're easy. I haven't looked at what
it would take to make a FET. Don't think it's that relevant to reply
with stuff about FETs to a post about bipolars. :-)
No, actually the FETs are easier to make than
a junction transistor.
> All
it requires is two diodes. That's
> all it is, really.
If you wire two diodes in series (PN->NP), it isn't the same as a
transistor (PNP), at all.
It is. A PNP is just the same thing as a PN-+-NP.
No, it is not a transistor. It is just two junctions that
will not show any transistor action.
Your understanding of how transistors work is flawed.
If you put two diodes back to back, it will not have
any gain. This is because ti current carrier will be
absorbed into the conductors.
The transistor works because the current is carried
in a material that the current carrier can exist for
a long time, like a static charge on an insulator yet
move around when a field is applied to it, like a conductor.
This is the important trait of a semi conductor that
makes the transistor work.
Now, it is important to realize that when we say that
the current carrier can exit for some length of time
without combining, we are still talking about very
small dimensions. In a transistor, the emitter junction
and collector junction have to be very close togather
or the carriers that are injected into the base region
will be combined to easily with the major current carriers
in the base region and just be base current.
If they are close enough that the injected carrier
can get into the collectors depletion region and the
collector is properly biased relative to the base,
it will become collector current.
This all depends on the physical closeness of the
emitter junction to the collector junction.
Since FETs are a surface effect, they are easier to
create.
The first commercial transistors were made by carefully
grinding the base material down until it was very thin
and then diffusing the collector and emitter junctions
into the surfaces from the two sides.
It wasn't until later that it was realized that one
could diffuse both junctions from the surface that
a more practical transistor was created.
Dwight
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