Learning the given value for a bias resistor(jfets) off board

[Doctor Algernop]

This may be a stupid question but I've used the search feature for awhile looking for a layout of something that will allow me to test the particular bias resistor needed for my fet's off board that way when I solder them into place I don't require sockets or trimmers for biasing

[EBK]

I'm wondering if the answer to your question is simply a solderless breadboard.  Good way to test out and tweak just about anything before soldering.

[jubal81]

I'm wondering if the answer to your question is simply a solderless breadboard.  Good way to test out and tweak just about anything before soldering.

+1

Just build up the stage on the breadboard, dial it in, then transfer the parts to your PCB for soldering.

$4.95 for this small one - great for quick testing little things.

https://www.sparkfun.com/products/12002

[Frank_NH]

I was going to suggest building a JFET tester to determine Idss and Vp for your specific part, but Jubal81 is right.  Just get a small breadboard and test it there.  Shouldn't take too long to find a resistor which biases you JFET.  Make sure to label the parts so there's no mix up later when you solder them in !   

[R.G.]

pogo pins

[EBK]

pogo pins

R.G., I fear that you are being a bit too cryptic (for me, at least).  I know what pogo pins are, but just what are you suggesting that our dear doctor should do with them?   

[duck_arse]

pogo pins

I searched - still no idea what or how.

[bluebunny]

pogo pins

I searched - still no idea what or how.

This.  (Hadn't heard of it either...  Perhaps I ought to have done: I worked for Cray in a previous life.)

[EBK]

Yes, yes, but I'm still unable to see the connection (no pun intended). Please enlighten me.  What do pogo pins have to do with this?

looking for a layout of something that will allow me to test the particular bias resistor needed for my fet's off board that way when I solder them into place I don't require sockets or trimmers for biasing

[antonis]

This may be a stupid question but I've used the search feature for awhile looking for a layout of something that will allow me to test the particular bias resistor needed for my fet's off board that way when I solder them into place I don't require sockets or trimmers for biasing

Solderable male nail pin connectors..!!
(there aren't neither sockets nor trimmers..) 

[EBK]

This may be a stupid question but I've used the search feature for awhile looking for a layout of something that will allow me to test the particular bias resistor needed for my fet's off board that way when I solder them into place I don't require sockets or trimmers for biasing

Solderable male nail pin connectors..!!
(there aren't neither sockets nor trimmers..) 

That's what I was thinking too.  It meets the negative requirements, but so does a water balloon.

[antonis]

Risk management for accidents due to loose parts in relation with conductivity leads to use of water balloons...

[Frank_NH]

Back to the OPs question, if you're talking about a "standard" common source JFET gain stage, you can calculate the bias and required resistors pretty accurately (I have a spreadsheet which does this), BUT you need to know the actual Idss and Vp for your JFET.  Given the wide range of Idss and Vp variation for a given type like a J201, there is no substitute for measuring.  You can build a simple JFET tester pretty easily (for example, http://tagboardeffects.blogspot.com/2012/07/greatly-improved-jfet-matcher.html), and test all your JFETs and organize them in individual plastic bags with their Idss and Vp recorded.  Yeah, it's a bit of work, but...

If you don't like all of this fussing around, then use op amps...