Buffer with Dual N-Ch Jfets and Dual Power Supply - Page 3

vdi_nenna · 15th March 2019, 08:27 PM

Can I get an extra set of eyes on this?
Are the two B-grade BF861 Jfets listed exactly the same?

bf861 NXP RF JFET Transistors | Mouser

thanks.

rco3 · 15th March 2019, 08:46 PM

The ,215 parts come on a reel of 3,000. The ,235 parts come on a reel of 10,000. If you are producing large numbers of final product, you may find that ordering a reel of 10K gives you different statistics for part-to-part variation than three or four reels of 3,000. If you are buying a couple of dozen for your personal projects, I suspect the difference is irrelevant.

vdi_nenna · 15th March 2019, 08:50 PM

Going for the cheaper part.

vdi_nenna · 21st March 2019, 02:14 PM

I wimped out and only picked up 25 qty BF861 and 25 qty J113. Also 50 SOT-23 to SIP adapters. Still have a bunch of 2SK170 ranging from 3mA to over 20mA Idss.

Soekris DAC's output is off the R2R array and said to be 1.2V. Can a buffer be made with 15v rails that will produce at least that much output from the buffer?
B1 does it with +19v, so I'm guessing +/-15v rails can achieve at least 1.2v output.

vdi_nenna · 29th March 2019, 07:06 PM

When matching jfet Idss, when is the reading taken?
Is it the first mA reading one sees or after a certain amount of time or certain temp the jfet reaches?
I noticed the mA reading changes over time.

EUVL · 29th March 2019, 07:10 PM

Steady state, as in operation.

Patrick

vdi_nenna · 29th March 2019, 07:19 PM

Thanks Patrick. So if running them at 15v, leave the test run at 15v for good amount of time.

EUVL · 29th March 2019, 07:22 PM

Correct.

And if you use a heatsink (for thermal coupling), then it is best to test it as such.
But we are getting towards perfection now .....

Patrick

vdi_nenna · 29th March 2019, 07:31 PM

Happy to have finally gotten this question resolved.

Thanks!

vdi_nenna · 31st March 2019, 03:47 AM

I tested ten J113 jfets so far and lowest Idss so far is 17.17mA at 15v.
Can source resistance help?

15th March 2019, 08:27 PM	#21
vdi_nenna diyAudio Member Join Date: Oct 2000 Location: PA, USA	Can I get an extra set of eyes on this? Are the two B-grade BF861 Jfets listed exactly the same? bf861 NXP RF JFET Transistors \| Mouser thanks. __________________ I build, therefore I am. Do not create problems where there are none.

15th March 2019, 08:50 PM	#23
vdi_nenna diyAudio Member Join Date: Oct 2000 Location: PA, USA	Going for the cheaper part. __________________ I build, therefore I am. Do not create problems where there are none.

21st March 2019, 02:14 PM	#24
vdi_nenna diyAudio Member Join Date: Oct 2000 Location: PA, USA	I wimped out and only picked up 25 qty BF861 and 25 qty J113. Also 50 SOT-23 to SIP adapters. Still have a bunch of 2SK170 ranging from 3mA to over 20mA Idss. Soekris DAC's output is off the R2R array and said to be 1.2V. Can a buffer be made with 15v rails that will produce at least that much output from the buffer? B1 does it with +19v, so I'm guessing +/-15v rails can achieve at least 1.2v output. __________________ I build, therefore I am. Do not create problems where there are none.

29th March 2019, 07:06 PM	#25
vdi_nenna diyAudio Member Join Date: Oct 2000 Location: PA, USA	Question about matching When matching jfet Idss, when is the reading taken? Is it the first mA reading one sees or after a certain amount of time or certain temp the jfet reaches? I noticed the mA reading changes over time. __________________ I build, therefore I am. Do not create problems where there are none.

29th March 2019, 07:10 PM	#26
EUVL diyAudio Member Join Date: Oct 2003	Steady state, as in operation. Patrick __________________ xen-audio.com


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15th March 2019, 08:46 PM	#22
rco3 diyAudio Member Join Date: Oct 2006 Location: Space Coast, FL	The ,215 parts come on a reel of 3,000. The ,235 parts come on a reel of 10,000. If you are producing large numbers of final product, you may find that ordering a reel of 10K gives you different statistics for part-to-part variation than three or four reels of 3,000. If you are buying a couple of dozen for your personal projects, I suspect the difference is irrelevant.

29th March 2019, 07:19 PM	#27
vdi_nenna diyAudio Member Join Date: Oct 2000 Location: PA, USA	Thanks Patrick. So if running them at 15v, leave the test run at 15v for good amount of time. __________________ I build, therefore I am. Do not create problems where there are none.

29th March 2019, 07:22 PM	#28
EUVL diyAudio Member Join Date: Oct 2003	Correct. And if you use a heatsink (for thermal coupling), then it is best to test it as such. But we are getting towards perfection now ..... Patrick __________________ xen-audio.com

29th March 2019, 07:31 PM	#29
vdi_nenna diyAudio Member Join Date: Oct 2000 Location: PA, USA	Happy to have finally gotten this question resolved. Thanks! __________________ I build, therefore I am. Do not create problems where there are none.

31st March 2019, 03:47 AM	#30
vdi_nenna diyAudio Member Join Date: Oct 2000 Location: PA, USA	I tested ten J113 jfets so far and lowest Idss so far is 17.17mA at 15v. Can source resistance help? __________________ I build, therefore I am. Do not create problems where there are none.

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