Vero Jfet matcher help

[jdroost]

Hello.
I just built the simple greatly improved jfet matcher shown here.

http://tagboardeffects.blogspot.com/2012/07/greatly-improved-jfet-matcher.html

Seems to work good for matching j201s but I am not sure if or how I can get Idss and Vp values from my readings.
At 9.35 input voltage I am getting 1.100 and .096 dc volts on a typical j201.
Can somebody tell me if I can calculate these voltage numbers for any more information?

Sorry...this is new to me.

[PRR]

Welcome!

> tell me if I can calculate these voltage numbers for any more information?

You would think that site would explain it. (Also show schematic so you could understand.)

Without un-tangling that layout: *probably*.....

Your 1.1V _is_ the Vp (for some low but arbitrary test current)

0.096V/10 is 0.009,6 Amps or 9.6mA and is your Idss (for about 9Vds).

[PRR]

Uh, duh.... did we read the diagram??

(I admit I missed it.)

[reddesert]

Welcome!

> tell me if I can calculate these voltage numbers for any more information?

You would think that site would explain it. (Also show schematic so you could understand.)

Without un-tangling that layout: *probably*.....

Your 1.1V _is_ the Vp (for some low but arbitrary test current)

0.096V/10 is 0.009,6 Amps or 9.6mA and is your Idss (for about 9Vds).

tagboardeffects makes vero layouts from public schematics. Because the schematics are typically drawn and possibly copyrighted by other people, they don't post the schematics themselves.  In this case there is a link, at that page, to https://www.diystompboxes.com/smfforum/index.php?topic=29513.0, which will provide all the desired information.  In general, if the schematic is not provided, it can be found on the web, often here or at the "other forum" (FSB).

I built the super simple version of the JFET matcher (the one that is just a couple of resistors), as suggested by runoffgroove ; there is a schematic at Fig 10 of the Fetzer Valve webpage http://www.runoffgroove.com/fetzervalve.html. It works fine.

[MaxPower]

Sounds like a RG circuit. Search for jfet or fetmatch at geofex.