Pearl 3 Burning Amp 2023

I take a negative impression of this tester.

You can see the voltage of the 9V battery go down with subsequent measurements.

Flip over the Mega328 and look at the bottom of the PCB. You'll see that it includes a 5.0V regulator IC which converts the time-varying battery voltage, to a constant, unvarying, regulated 5.0 volts.

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It is not possible to predict just measuring the Idss using my Peak DCA75 tester?
Then I could maybe find another J112 that has "correct" Idss?

My approach is to measure the voltage in the circuit then use that voltage to find a pair of matching IDSS J112 jfets one for each left and right then select a pair of matching source resistors to provide the specified current.

Then after measuring and selecting the parts solder it all together.

That way both channels will be the same.

Thanks DT
 
I received the P3 kit and I did a measurement on the two J112 in the package using the DCA75. They are relative close to each other. I think close enough.
The DCA75 reads out these parameters:

Vgs_off: -3.84V, -3.63V
Vgs_on: -2.85V, -2.65V
gfs: 9.1mA/V, 8.8mA/V
Idss: 12.0mA, 12.0mA
Rds_on: 27.7 ohm, 28.0 ohm

I will probably do the measurement Dennis Hui suggested and if inside the bias interval I think I am good to go with these two J112.

The J112 is not operated at Vgs = 0 in P3 circuit but Vgs will be a bit negative. Then bias current will be less than 12mA......but I am not able to calculate in my head what the result will be "in-circuit".
 
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