On 7/2/2018 3:17 AM, Tim Shoppa wrote:
I believe the old Clifton Labs pages had some nice info on JFET parameters.
Can't get to anymore?
W7ZOI has a nice page on measuring IDSS which I recall to be the parameter
on the spec sheet most relevant: http://w7zoi.net/jfet101.pdf
Measuring IDSS only takes a 10V power supply and a milliameter, very easy.
It is not unusual for JFETs/MOSFETs to have a specified IDSS that covers
a range of 10:1. Any experimenter should get proficient at measuring
IDSS and understanding how it matters to the application circuit.
Also, the IDSS of a particular batch might be in a much narrower range,
but the next batch is not guaranteed to repeat.
HP used a FET in one of their products where it was easy to calculate
that the circuit would not work over the full specified range of IDSS.
In spite of this, the product successfully shipped for a few years ...
until the latest batch of FETs didn't work, due to a change in IDSS.
Rick N6RK
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