Beginners JFET FAQ

Dr.H · 8th September 2011, 01:47 PM

Perhaps we can start a FAQ here?
I've got a basic question:
I've looked at the Id vs Vds charts (with varying Vgs) and it all makes sense.

But, say I have a J310 and I'd like to build a simple buffer.

How do I choose the appropriate Vds for my application? What am I trying to optimise in the choice of Vds?

Nelson Pass · 8th September 2011, 02:41 PM

Choice of Vds is simple enough, as it mostly considers

1) How much output swing do you need? (Vds has to be higher than that)

2) What is the maximum Vds of the part? (Vds has to be lower than that)

3) What is the load? (The Ids x Vds has to be less than the part can dissipate)

Dr.H · 8th September 2011, 03:50 PM

Thanks Nelson, appreciate the steer. I also came across Designing JFET Audio PreAmplifiers

Bksabath · 9th September 2011, 12:58 AM

Dr H
tanks for posting that link
Just about what I can bite and chew on.

Now I wants more.
IMO this tread

Bksabath · 11th September 2011, 09:39 AM

I think I have found more
possibly more than I can chew but..

Gogle up Horowitz and The art of electronics

Nelson Pass · 11th September 2011, 11:43 PM

Horowitz and Hill, The Art of Electronics

also known as the Bible.

buzzforb · 11:58 PM

Although the link is helpful, I find there is a gap between common electronic knowledge and what makes for good audio amplification. Too many subtle influences between good and great. Ultimately I believe the thing that separates the good from the mediocre, is sheer experience. Best teacher is just trying and possibly failing. Nelson probably has a notebook collection of info/practical experience that would baffle most people.

transistormarkj · 12th September 2011, 12:15 AM

Pretty good book by the staff at Siliconix (later sold to Vishay) -- see attachment

Also, if you can find it, "FET Circuits" by Rufus P. Turner, ISBN 0672214393 (0-672-21439-3)

Peter M. · 12th September 2011, 02:40 PM

I just found this:

Foolin' with FETs

homemodder · 12th September 2011, 03:00 PM

I think the most helpfull info on Jfet use in audio is the articles by Boberly. I dont think they are still available on the net but if anyone is interested I could send by email.

Borbely practically only used Jfets and mosfets in his designs.

The rest you can read up on Horowitz and Hill.

8th September 2011, 01:47 PM	#1
Dr.H diyAudio Member Join Date: Apr 2002	Beginners JFET FAQ Perhaps we can start a FAQ here? I've got a basic question: I've looked at the Id vs Vds charts (with varying Vgs) and it all makes sense. But, say I have a J310 and I'd like to build a simple buffer. How do I choose the appropriate Vds for my application? What am I trying to optimise in the choice of Vds?

11th September 2011, 11:55 PM	#7
buzzforb diyAudio Member Join Date: Oct 2010 Location: Burlington, NC	Although the link is helpful, I find there is a gap between common electronic knowledge and what makes for good audio amplification. Too many subtle influences between good and great. Ultimately I believe the thing that separates the good from the mediocre, is sheer experience. Best teacher is just trying and possibly failing. Nelson probably has a notebook collection of info/practical experience that would baffle most people. Last edited by buzzforb; 11th September 2011 at 11:58 PM.

12th September 2011, 02:40 PM	#9
Peter M. diyAudio Member Join Date: Jan 2005 Location: Østfold	I just found this: Foolin' with FETs __________________ Note to myself: Never again use fingers to check if there still is voltage left in a capacitor...

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
FS: PreAmp with Complimentary JFET Diff input & JFET ouput	USAcircuits	Vendor's Bazaar	12	21st June 2011 11:02 AM
FAQ We Get at DIYHFS	bcherry	DIY HiFi Supply	0	4th August 2010 01:46 AM


	Please consider donating to help us continue to serve you. Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving

8th September 2011, 02:41 PM	#2
Nelson Pass The one and only Join Date: Mar 2001	Choice of Vds is simple enough, as it mostly considers 1) How much output swing do you need? (Vds has to be higher than that) 2) What is the maximum Vds of the part? (Vds has to be lower than that) 3) What is the load? (The Ids x Vds has to be less than the part can dissipate)

8th September 2011, 03:50 PM	#3
Dr.H diyAudio Member Join Date: Apr 2002	Thanks Nelson, appreciate the steer. I also came across Designing JFET Audio PreAmplifiers

9th September 2011, 12:58 AM	#4
Bksabath diyAudio Member Join Date: Dec 2007	Dr H tanks for posting that link Just about what I can bite and chew on. Now I wants more. IMO this tread

11th September 2011, 09:39 AM	#5
Bksabath diyAudio Member Join Date: Dec 2007	I think I have found more possibly more than I can chew but.. Gogle up Horowitz and The art of electronics

11th September 2011, 11:43 PM	#6
Nelson Pass The one and only Join Date: Mar 2001	Horowitz and Hill, The Art of Electronics also known as the Bible.

12th September 2011, 03:00 PM	#10
homemodder diyAudio Member Join Date: May 2006	I think the most helpfull info on Jfet use in audio is the articles by Boberly. I dont think they are still available on the net but if anyone is interested I could send by email. Borbely practically only used Jfets and mosfets in his designs. The rest you can read up on Horowitz and Hill.

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read