nfet calculator

[diydave]

Ok, bit scared in posting this, but I will take my chances.
Frequently the question arises in how to bias a nfet (like a j201). There is the "trimpot-on-drain"-method, which works.
But I like to know in advance what I'm doing and where I'm heading, rather than trimming a pot until I like what I hear.

So for some time I made up a spreadsheet which calculates 9 Vgs-voltages (based on the pinch-off voltage of the fet) and the appropriate Id, Source-resistor and Drain-resistor. I transformed it to a webthing.

This is the link: www.diydave.be/tools/fetcalc/index_eng.html.

I hope it is usefull for somebody. It sure is helpfull to me in getting baising a fet the way I want(near cut-off, very hot, etc...), without the trimpot.
I'm working to add a graph for the Vgs-Id curve, so there is a visual aid to choose a biaspunt and thus the source and drian resistors.

[deadastronaut]

NICE...bookmarked.. thanks.

[alfafalfa]

Thanks , this might come in very handy.

[peterv999]

Thanks very much!
-piet

[diydave]

update.

Managed to plot a Vgs - Id transfer-curve alongside the table.
The graph shows the varies Vgs points.

[robmdall]

Nice. Thanks!

[sault]

Dangit - you beat me to it! I've been wanting to take the time to sit down and write an application very similar to this one for quite some time now... kudos on doing such a good job at it!



Saul t

[diydave]

Thx.
Glad it's helpful.