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TOPIC: Measuring 100 JFET J201 Transistors.

Measuring 100 JFET J201 Transistors. 3 years 2 months ago #355

  • Ray
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I have recorded the Vgs(off) and IDss of one hundred J201 JFET transistors taken from a reliable US source.

This could help you if you want to design some J201 based circuit and want to have a clear idea f what is out there.

For the measurements I have used a Peak Atlas DCA Pro (model DCA75) which is one of the best dedicated transistor meter on the market. It would help to give a constant set of values.

peak-dca-pro-j201.jpg



Small Bear Electronics J201 Transistors Measurement
                     	Vgs[off](V)	Idss(mA)
J201 JFET no 01		-0.87		0.75
J201 JFET no 02		-0.95		0.87
J201 JFET no 03		-0.95		0.87
J201 JFET no 04		-0.76		0.60
J201 JFET no 05		-0.96		0.86
J201 JFET no 06		-0.89		0.77
J201 JFET no 07		-0.93		0.82
J201 JFET no 08		-0.93		0.81
J201 JFET no 09		-0.77		0.60
J201 JFET no 10		-0.85		0.71
J201 JFET no 11		-0.81		0.66
J201 JFET no 12		-0.65		0.45
J201 JFET no 13		-0.87		0.76
J201 JFET no 14		-0.74		0.58
J201 JFET no 15		-0.80		0.65
J201 JFET no 16		-0.73		0.57
J201 JFET no 17		-0.94		0.82
J201 JFET no 18		-0.97		0.86
J201 JFET no 19		-0.90		0.78
J201 JFET no 20		-0.81		0.67
J201 JFET no 21		-0.78		0.63
J201 JFET no 22		-0.65		0.45
J201 JFET no 23		-0.72		0.56
J201 JFET no 24		-0.82		0.68
J201 JFET no 25		-0.93		0.85
J201 JFET no 26		-0.84		0.69
J201 JFET no 27		-0.82		0.68
J201 JFET no 28		-0.85		0.72
J201 JFET no 29		-0.85		0.71
J201 JFET no 30		-0.73		0.55
J201 JFET no 31		-0.82		0.69
J201 JFET no 32		-0.85		0.70
J201 JFET no 33		-0.94		0.86
J201 JFET no 34		-0.91		0.79
J201 JFET no 35		-0.72		0.55
J201 JFET no 36		-0.96		0.87
J201 JFET no 37		-0.79		0.63
J201 JFET no 38		-0.74		0.57
J201 JFET no 39		-0.85		0.72
J201 JFET no 40		-0.78		0.62
J201 JFET no 41		-0.76		0.58
J201 JFET no 42		-0.83		0.68
J201 JFET no 43		-0.96		0.83
J201 JFET no 44		-0.82		0.69
J201 JFET no 45		-0.73		0.57
J201 JFET no 46		-0.90		0.78
J201 JFET no 47		-0.95		0.86
J201 JFET no 48		-0.73		0.56
J201 JFET no 49		-0.95		0.85
J201 JFET no 50		-0.96		0.85
J201 JFET no 51		-0.73		0.57
J201 JFET no 52		-0.73		0.57
J201 JFET no 53		-0.88		0.76
J201 JFET no 54		-0.92		0.83
J201 JFET no 55		-0.92		0.85
J201 JFET no 56		-0.93		0.84
J201 JFET no 57		-0.70		0.55
J201 JFET no 58		-0.87		0.78
J201 JFET no 59		-0.87		0.79
J201 JFET no 60		-0.89		0.80
J201 JFET no 61		-0.77		0.64
J201 JFET no 62		-0.91		0.80
J201 JFET no 63		-0.72		0.59
J201 JFET no 64		-0.72		0.57
J201 JFET no 65		-0.89		0.80
J201 JFET no 66		-0.83		0.72
J201 JFET no 67		-0.76		0.64
J201 JFET no 68		-0.80		0.69
J201 JFET no 69		-0.84		0.73
J201 JFET no 70		-0.84		0.69
J201 JFET no 71		-0.76		0.62
J201 JFET no 72		-0.80		0.67
J201 JFET no 73		-0.82		0.68
J201 JFET no 74		-0.91		0.79
J201 JFET no 75		-0.97		0.88
J201 JFET no 76		-0.74		0.58
J201 JFET no 77		-0.74		0.58
J201 JFET no 78		-0.86		0.75
J201 JFET no 79		-0.82		0.73
J201 JFET no 80		-0.74		0.60
J201 JFET no 81		-0.61		0.46
J201 JFET no 82		-0.90		0.78
J201 JFET no 83		-0.72		0.54
J201 JFET no 84		-0.86		0.69
J201 JFET no 85		-0.71		0.55
J201 JFET no 86		-0.99		0.84
J201 JFET no 87		-0.89		0.81
J201 JFET no 88		-0.92		0.88
J201 JFET no 89		-0.78		0.63
J201 JFET no 90		-0.94		0.88
J201 JFET no 91		-0.89		0.73
J201 JFET no 92		-0.78		0.58
J201 JFET no 93		-0.94		0.81
J201 JFET no 94		-0.83		0.67
J201 JFET no 95		-0.92		0.83
J201 JFET no 96		-0.90		0.80
J201 JFET no 97		-0.91		0.82
J201 JFET no 98		-0.95		0.80
J201 JFET no 99		-0.90		0.78
J201 JFET no 100	-0.94		0.83
 
Average Value	    -0.834V	    0.704mA

Tayda Electronics J201 Transistors Measurement
			Vgs[off](V)     Idss(mA)
J201 JFET no 01		-0.91		0.8
J201 JFET no 02		-0.93		0.82
J201 JFET no 03		-0.79		0.62
J201 JFET no 04		-0.74		0.59
J201 JFET no 05		-0.81		0.63
 
Average Value		-0.84V		0.71mA

These are a set of screen shots you can take using the Peak DCA Pro software, they show the Id vs Vds and the Id vs Vgs plots. I did them overlaying the measurements of 4 different J201 JFET transistors, to prove that the graphs are pretty consistent.

image001.jpg


JFETid_Vds.png


JFETid_Vgs.png


Conclusion:

The average values after reading 100 JFETs are:
  • Vgs(off) = -0.83V
  • Idss = 0.70mA

This values are very close to the ones measured by Run off Groove (Vgs(off)=-0.84V and Idss=0.64mA) in his great article A closer look at the Fetzer Valve.

The components tested above are from Small Bear Electronics, a reliable US components supplier. I also ordered 5 transistors from Tayda Electronics, in internet forums [1] [2] some folks were questioning this components, not being sure of getting fake parts or relabeled transistors.
From my measurements and as far as I know the J201 from Tayda are good and within the datasheet specifications with average values also very close to the expected ones (Vgs(off)=-0.84V and Idss=0.71mA)
Last Edit: 3 years 1 month ago by Ray.
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Measuring 100 JFET J201 Transistors. 2 years 4 months ago #520

  • kiyo
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Hi!

What JFET do you recommend if we can't find J201?

Thank you very much!
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Measuring 100 JFET J201 Transistors. 2 years 4 months ago #521

  • Ray
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Hi,
There is plenty of information online about the J201 substitute:
- J201 Substitute in diystompboxes
- J201 Substitute in madbeanpedal
- J201 Substitute in ssguitar.com


The J201 is quite unusual and it is still manufactured but in SMD model (not thuhole), some folks use a sot23 to thuhole adapter that works fine with some extra work.
Righ now I have checked mouser and they have J201 in stock (smd and thruhole models):
http://www.mouser.co.uk/All-Manufacturers/_/N-0?Keyword=j201+transistor&FS=True

However, if you are using for a different model, maybe the closest jfet you can get is the 2N5457, 2N5458 or MPF102.
You may need to adjust some resistors using this procedure:

jfet-amplifier-calculation-small.jpg
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Measuring 100 JFET J201 Transistors. 2 years 4 months ago #522

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Thank you very much Ray!

I live in Brazil, and unfortunately the shipping cost is very high so I will try to find some substitutes.

Thanks again!
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Measuring 100 JFET J201 Transistors. 2 years 4 months ago #527

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Im not aware of suppliers for jfets in Brazil, maybe asking in audio forums you can get some ideas. However finding alternative parts and adjusting them to your circuit is fan and can lead you to new sounds :woohoo:
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Measuring 100 JFET J201 Transistors. 2 years 4 months ago #530

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Yeah, I just found a bunch of 2N3819 in a local electronics store. I'll play with them and have some fun, hehe.

Thank you very much Ray! This website is amazing, I learn a lot with it every day.

Best regards!
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