On 18/09/2018 20:12, Gareth's Downstairs Computer wrote:
One thing puzzles me, why does it matter if a FET is put into
a circuit the wrong way around, with source and drain interchanged,
because a FET (JUGFET, MOSFET) is symmetrical in its construction?


It depends.

Some FETs are symmetric and should, in theory, work if 'reversed'. In
JFETs it depends on the doping process. From memory, if a double
diffusing process is used you're out of luck- but that is just from memory.

Strictly speaking, symmetric JFETs are the only ones where the arrow
should join the bar at mid-point in the symbol. The others it should be
offset. Having said that, I've rarely seen that applied.



--

Smile for the camera ;-)
https://www.youtube.com/watch?v=HxyL2_38EsQ
Remarkable Coincidences:
The Stock Market Crashes of 1929 and 2008 happened on the same
date in October. In Oct 1907, a run on the Knickerbocker Trust
Company led to the Great Depression.