Electronics > Repair
Transistor Jfet HP equivalent
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schmitt trigger:

--- Quote from: dacman on January 29, 2017, 09:45:25 pm ---Conductance

For Conductance or On Resistance:
1) Clip the negative lead of a DMM onto both the Source and Gate.
2) Clip the positive lead onto the Drain.
3) Measure Resistance.
4) The reciprocal would be the conductance.


--- End quote ---

Is conductance somewhat related to Idss? The test setup appears similar.
Kleinstein:
There is a strong correlation between the JFET parameters.  There are tables on the relations in text books and application notes on JFETs ( e.g. Fairchild AN6609).   Ron is about equal to  1/ Gfs0 .  gfs0 is about  2 Idss / Vgs_off.    This is at least a reasonable approximation.

Vgs_off anyway scatters quite a bit between batches and with V_gs_off also R_on and Idss change. From the same series (e.g. J111 to J113), part with the higher Vgs_off will still have the low R_on as Idss goes up even faster than Vgs_off (more like the square).
Wallace Gasiewicz:
First: Thanks to Kleinstein for the post about Gate Leakage. I think I now understand why same FETs were used.
About the "setup" for R On and IDSS:   
Setup is the same but the voltages are far different.  The voltage (Drain to Source) for IDSS are higher than what is used to measure R On.  Increase the voltage enough and you will reach IDSS. At that point the FET is Saturated and resistance will be much higher, You are out of the Ohmic Region of the FET.
fmashockie:
Just FYI although I don't see the 1855-0743 listed, CuriousMarc's website has an archive of proprietary HP part #s and their electrical specs.  It is not a complete list, but it has definitely come in handy for me.

https://www.curiousmarc.com/doc-archive
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