The 3N200 and others (3N204, 40820, 40822) can still be found at Dan's Small
Parts - see:
http://www.danssmallpartsandkits.net/ .
Price is $5 each which is a bit stiff but considering that there aren't many
shows in town, I think I'd buy some spares if I had a need.
Other than buying parts from, I have no connection with this dealer.
Tom - WA2BPE
"Dr. Gerald N. Johnson, electrical engineer" wrote:
> Since double gate MOSFET transistors are no longer being made in
> silicon, supplying modified transistors is more than a little difficult.
> Seems to me that the forward transconductance of 10 to 15 millimhos is
> normal for the 3N200, and IDS will have some variations from transistor
> to transistor. There might need to be some selection, but since they
> haven't been made in several years, finding them in a quantity of 2500
> after selection may be impossible. I have no source. You can do an
> internet search on the part number, there are a few places with stocks
> of obsolete transistors that may be able to supply. I doubt the makers
> of obsolete transistors have made any because the silicon double gate
> MOSFET went out of production because the production machinery was based
> on 2" diameter silicon wafers and the vendors of silicon wafers scrapped
> all their crystal growing equipment that small.
>
> NTE Electronics latest cross reference shows a replacement using their
> NTE-222. Last I priced it, it was fairly expensive. The specifications
> for it show IDS can have a range of 5 to 35 ma, and Gm is typically 12
> millimhos. It may be possible to select transistors from their stock to
> meet your specifications.
>
> Gerald J.
> --
> Entire content copyright Dr. Gerald N. Johnson, electrical engineer.
> Reproduction by permission only.
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