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Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets. |
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24th Jun 2020, 3:36 pm | #1 |
Octode
Join Date: Feb 2006
Location: Bristol, UK.
Posts: 1,030
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2N3819 pinout
Looking at a 2n3819 FET for a 90MHz preamp for my old Cossor. There is a difference of opinion on the internet about the pin out arrangement.
With the flat uppermost and the leads towards you, some give the arrangement ,reading left to right, as D,G,S and others give it as S,G,D. The Fairchild data sheet gives the DSG arrangement so this is what I shall be using. Though why other sites give a different pinout I don't know. Malcolm |
24th Jun 2020, 3:50 pm | #2 |
Heptode
Join Date: Jul 2012
Location: Bromley, London, UK.
Posts: 702
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Re: 2N3819 pinout
IIRC the FET is pretty much symmetrical, so S and D are effectively the same. Have a look at this old thread: https://www.vintage-radio.net/forum/...d.php?p=909109.
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24th Jun 2020, 4:08 pm | #3 |
Octode
Join Date: Feb 2006
Location: Bristol, UK.
Posts: 1,030
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Re: 2N3819 pinout
That thread answers my question.
Thanks |
24th Jun 2020, 4:14 pm | #4 |
Moderator
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 22,800
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Re: 2N3819 pinout
There are some tricks with symmetrical FETs.
In SSB transceivers where filters and IF structures are operated in one direction for receive and the opposite direction for transmit, it's usual to have lots of switches reversing the inputs and outputs of amplifiers. With symmetrical FETs the positive feed for the drain can be swapped to the source, and the amplifier amplifies in the reverse direction. Whoever thought of that one was a very smart cookie! David
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