The New-Tron - Page 8

Nelson Pass · 27th May 2006, 08:01 PM

Yes, this is definitely a Class A circuit.

As to the cascode, you can approach it either way, I don't think
it's going to make a lot of difference. Self biased JFETs are
elegant, but you have to take the voltage they offer.

EUVL · 27th May 2006, 09:14 PM

May I ask for one more hint ?

Suppose I only want 10-15W Class A (just to drive tweekers), and I want to use Loveltech Power JFETs with Cascode as output, like Grey is proposing. I guess I would be biasing single JFET at 1.3A (2 Power JFETs per channel). Would I still be able to use the triode parts of the curves ? I have no Power JFETs on hand yet, and there is insufficient information on the datasheet. What would be the best cascode voltage ?

Many thanks in advance,
Patrick

Nelson Pass · 27th May 2006, 10:09 PM

Of course. You get to the triode part of the curve by operating
at the lower voltages, and the cascoding can easily be set for
any operating point you want. It's just lucky that the spot you
want is 2-3 volts or so, so the dissipation will be low on the JFET.

EUVL · 28th May 2006, 05:08 AM

Any chance of publishing some measurements (Id vs Vds for various fixed Vgs) around that region ?

Most grateful,
Patrick

jh6you · 29th May 2006, 03:58 AM

Quote:

Originally posted by Nelson Pass

Kirchoff's Law dictates that the circuit will not work unless there
is some DC attachment from the input circuit to the output
circuit to allow a difference in drive current to the output devices.

Aha . . . Kirchoff's rule . . .

The basic is almost same as shear flow analysis with multicells we are working on it daily.

By the way, I was always confused if the simultaneous linear equaions are more than two. Never improved yet . . .

Regards

JH

Nelson Pass · 30th May 2006, 05:10 PM

Quote:

Originally posted by EUVL
Any chance of publishing some measurements (Id vs Vds for various fixed Vgs) around that region ?

You are in the region where it varies quite a bit. If you check
ZV9, you'll get some incomplete information.

EUVL · 2nd June 2006, 08:47 AM

> You are in the region where it varies quite a bit. If you check ZV9, you'll get some incomplete information.

Had done so already before asking. Guess I just have to wait until the JFETs arrive, whenever that might be.

In the meantime, this is the first attempt for the power JFET version. Of course you are right, the MOSFET version published earlier here has very little gain. This should have about 30dB at 4 ohms, and is, at least according to quick hand calculations, stable to over 1MHz.

The over-current protection is probably not quite sufficient, but I have not figured out an elegant way of doing that yet.

Should I expect expect quite a bit of thermal drift for the Power JFETs, bearing in mind their very high transconductance ?

Patrick

EUVL · 2nd June 2006, 02:33 PM

Firstly my apologies for posting the wrong schematics. It was of course not the one with Power JFET, but the previous MOSFET circuit.

It had taken some time and I still could not make the file small enough for posting, so we'll have to do it in two halves.

This is the overall view.

Patrick

EUVL · 2nd June 2006, 02:34 PM

And the left hand half in pdf.
Right hand half is identical but mirrored.

Patrick

gl · 14th June 2006, 06:37 PM

Hi Grey,

How is the development of the New-tron going? There have been lots of ideas floating around on this thread. Have you made any further updates or had any further progress? Thanks.

Cheers,
Graeme

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
Tron Seven	reinhard	Tubes / Valves	2	30th April 2008 12:26 AM
Tron Syren	analog_sa	Tubes / Valves	2	13th April 2005 09:05 AM

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


	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

27th May 2006, 08:01 PM	#71
Nelson Pass The one and only Join Date: Mar 2001	Yes, this is definitely a Class A circuit. As to the cascode, you can approach it either way, I don't think it's going to make a lot of difference. Self biased JFETs are elegant, but you have to take the voltage they offer.

27th May 2006, 09:14 PM	#72
EUVL diyAudio Member Join Date: Oct 2003	May I ask for one more hint ? Suppose I only want 10-15W Class A (just to drive tweekers), and I want to use Loveltech Power JFETs with Cascode as output, like Grey is proposing. I guess I would be biasing single JFET at 1.3A (2 Power JFETs per channel). Would I still be able to use the triode parts of the curves ? I have no Power JFETs on hand yet, and there is insufficient information on the datasheet. What would be the best cascode voltage ? Many thanks in advance, Patrick

27th May 2006, 10:09 PM	#73
Nelson Pass The one and only Join Date: Mar 2001	Of course. You get to the triode part of the curve by operating at the lower voltages, and the cascoding can easily be set for any operating point you want. It's just lucky that the spot you want is 2-3 volts or so, so the dissipation will be low on the JFET.

28th May 2006, 05:08 AM	#74
EUVL diyAudio Member Join Date: Oct 2003	Any chance of publishing some measurements (Id vs Vds for various fixed Vgs) around that region ? Most grateful, Patrick

14th June 2006, 06:37 PM	#80
gl diyAudio Member Join Date: Dec 2003 Location: Sierra Foothills - California	Hi Grey, How is the development of the New-tron going? There have been lots of ideas floating around on this thread. Have you made any further updates or had any further progress? Thanks. Cheers, Graeme