(tr)uSDX Forum

Is there a simple way to match my stock of bs-170? I would like to install them closely matched.
I tried some of the simple jfet matching multimeter circuits on the web but they did work for these bs170.
When I do simple gate/source/drain go/no go test with a multimeter, they seem to test more like a mosfet than a jfet. I could not get any bs170 to work in a simple matching circuit.
Any good matching circuits out there?

The way I would do it is to turn on the gate with a specific voltage and then measure RDS in that "on" state. Do this for all your devices and match them by RDS On.

73,

Robert, WA2T

The Gate Threshold voltage on the data sheet I looked at (OnSemi) says 2.1V typical. So, that would be around where to start while looking at RDS. Settle on a VGS that gives meaningful RDS values and then test all the devices you have for RDS at that same VGS.

Thank you for your answers to my question.
As much as I hate to admit it, I have no clue what you are talking about. My fault not yours. I"m sure your answer is meaningful to most but sadly, If I can't measure it easily with a meter or scope, or see it on a spectrum analyzer, I am lost. I am unable to do math of any complexity, and for me simple algebra is way over my head.
I try and make up for zero education by buying test equipment, and it has mostly worked out for me. Odd hobby for someone like me to be involved in but I do love it.
So I am hoping for a simple circuit I can lash up that will let me plug in all my jfets and read on a meter some value of comparison.
Thanks again

Hello OM,

you can buy a LCR T4 tester.
It is around 10 us$ from China or a little bit more from your country
I found one on ebay for you number: 324875600790
It measures Threshold voltage and Input Capacitance, and you can match your Fets with it.
Nobody measures Rdson for matching FETs, normally they are matched with Threshold Voltage and IDss.
But i also have to say it is not important to match MosFETs if you have all from the same batch, which is likely when you buy 10 at one time.
Semiconductors today have a very small variation on one wafer in Silicon, and if you get one of these from one wafer they are matched very good enough for our application here.
Semiconductor FETs are not electron tubes although FETs behave approximately like tubes.

73 de Chris

https://sites.google.com/site/g4zfqradi ... r-softrock
Matching a couple is not too hard, find 3 is something else...

Good info Owen.

Power comes in from connector on left, the two wires go to the multimeter

Wow thanks to everyone for their suggestions. I now have several options and I also purchased the transistor tester that was suggested to me. All good stuff!
You guys are awesome!