Your ammeter in the supply feed also drops voltage. This results in a variable Vds as Idss changes.
You could swap the 100r to 10r or even 1r0 for a much lower voltage change with changing Idss.
A 199.9mVdc DMM scale will read to 0.1mV across 1r0 and show a resolution of 0.1mA which is good enough for rough batching of Idss.
When you have a batch that are within 0.5mA of Idss, you can increase the resistor to 10r or 20r for a finer resolution of the Idss. Far better than using an ammeter.
You could swap the 100r to 10r or even 1r0 for a much lower voltage change with changing Idss.
A 199.9mVdc DMM scale will read to 0.1mV across 1r0 and show a resolution of 0.1mA which is good enough for rough batching of Idss.
When you have a batch that are within 0.5mA of Idss, you can increase the resistor to 10r or 20r for a finer resolution of the Idss. Far better than using an ammeter.
My 'good' calibrated one measures 2.2 Ohm resistance for my el cheapo one in mA series mode including the leads of course. So the cheap DMM will change VDS by 0.022V when in line with a 10mA IDSS mode JFET. Not bad in my book. The better one claims 0.15% accuracy in DCmA range. The economic one 0.8%.
Relativity
As I have the smaller PSU handy, I will just test Vp w/o my bipolar supply. I can never get absolute accuracy with my present bench tools. What is important is the relative test results I get from my batch of jfets.
I've done a tentative breadboard layout of the V1.2 shunt, attached. Not all parts are correctly sized yet. More of a general layout concept.
Thanks all for continued support.
-Kent
As I have the smaller PSU handy, I will just test Vp w/o my bipolar supply. I can never get absolute accuracy with my present bench tools. What is important is the relative test results I get from my batch of jfets.
I've done a tentative breadboard layout of the V1.2 shunt, attached. Not all parts are correctly sized yet. More of a general layout concept.
Thanks all for continued support.
-Kent
Attachments
Use the left one you posted with 1M. It will do the same job with just a battery.
Make your interstage caps smaller if you already got expensive output caps that could be smaller to your line load. Any extra strong filter will mean op amps or other active elements. If you want to go that route, classic op amp filters 24dB are just a google's stroke away.
I'm not comfortable changing the interstage cap, I think the problem is the output cap because my Erno Borbely preamp has an input impedance of 1Meg so for 3.9uF output cap the optimal low frecuency reponse is 0.41Hz, with a output cap of 0.08uF will be 20Hz & fix the problem, right?
P.S. What about the sun, beach & drink?
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Hi Salas
Your obviously a fan of the movie.
I've been waiting to ask someone this a while.
On my DVD copy there seems to be an incredibly subtle wobbling type effect going on with the B&W bits at the begining.
I can't work out if it's a bad DVD transfer or in fact an original Tarkovsky optical effect.
Ever noticed that.
I find it very weird, and no my TV's not on the blink.
Great soundtrack on that film.
Simon
Your obviously a fan of the movie.
I've been waiting to ask someone this a while.
On my DVD copy there seems to be an incredibly subtle wobbling type effect going on with the B&W bits at the begining.
I can't work out if it's a bad DVD transfer or in fact an original Tarkovsky optical effect.
Ever noticed that.
I find it very weird, and no my TV's not on the blink.
Great soundtrack on that film.
Simon
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0.033uF teflon capacitor items - Get great deals on Electronics items on eBay.com!
I have on hand 0.047uF 200VDC, if I use these wich is the corner frecuency?
0.033uF teflon capacitor items - Get great deals on Electronics items on eBay.com!
I have on hand 0.047uF 200VDC, if I use these wich is the corner frecuency?
There is in mine too. Must have been the telecine transfer machine.