Supertex dn2540 CCS Rset trimmer value - diyAudio
Go Back   Home > Forums > Amplifiers > Tubes / Valves

Tubes / Valves All about our sweet vacuum tubes :) Threads about Musical Instrument Amps of all kinds should be in the Instruments & Amps forum

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
Reply
 
Thread Tools Search this Thread
Old 3rd July 2012, 03:52 PM   #1
Account disabled at member's request
 
Join Date: Jul 2009
Default Supertex dn2540 CCS Rset trimmer value

I have read all available threads (also the "suggested" threads when writing this post) but to no avail.

I woul oike to use both the supertex dn2540 and IXYS 10m45s part as single device CCS

To do that I must select an appropriate Rset value (2.2k gate stoppers on each device).

The application requires 3mA and 5mA (both the supertex device and IXYS device will have to provide either one or the other). With a 2.2k gate stopper I thought of adding a 5k multiturn linear trimmer on the IXYS devices but I am not sure the same value would work for the supertex part.
The datasheet for the IXYS device does provide a graph with the Rset to current relationship however there the supertex datasheet does not.

Could someone please address the following questions?

1. Is a 5k multiturn pot a good choice to precisely achieve 3mA or 5mA from either device as a plate CCS? Is a larger value (ie 10k) better for such small currents?

2. What exactly is the correct value for each device (single IXYS and single SUPERTEX) to achieve 3mA and 5mA?

Thank you for any reply

Cheers
  Reply With Quote
Old 3rd July 2012, 04:45 PM   #2
diyAudio Member
 
Michael Koster's Avatar
 
Join Date: Jan 2008
Location: Eureka, CA
Quote:
Originally Posted by Alexontherocks View Post
I have read all available threads (also the "suggested" threads when writing this post) but to no avail.

I woul oike to use both the supertex dn2540 and IXYS 10m45s part as single device CCS

To do that I must select an appropriate Rset value (2.2k gate stoppers on each device).

The application requires 3mA and 5mA (both the supertex device and IXYS device will have to provide either one or the other). With a 2.2k gate stopper I thought of adding a 5k multiturn linear trimmer on the IXYS devices but I am not sure the same value would work for the supertex part.
The datasheet for the IXYS device does provide a graph with the Rset to current relationship however there the supertex datasheet does not.

Could someone please address the following questions?

1. Is a 5k multiturn pot a good choice to precisely achieve 3mA or 5mA from either device as a plate CCS? Is a larger value (ie 10k) better for such small currents?

2. What exactly is the correct value for each device (single IXYS and single SUPERTEX) to achieve 3mA and 5mA?

Thank you for any reply

Cheers
All will be less than 1K. A smaller value pot is better to make the adjustment less sensitive. I'd use a 1K pot.
  Reply With Quote
Old 3rd July 2012, 04:57 PM   #3
Account disabled at member's request
 
Join Date: Jul 2009
I checked again the IXYS 10m45s datasheet. Actually according to the datasheet 1k would seem to be exactly the value needed for 3mA.

However the dn2540 part usually requires a higher value no?
  Reply With Quote
Old 3rd July 2012, 05:32 PM   #4
diyAudio Member
 
Michael Koster's Avatar
 
Join Date: Jan 2008
Location: Eureka, CA
Quote:
Originally Posted by Alexontherocks View Post
I checked again the IXYS 10m45s datasheet. Actually according to the datasheet 1k would seem to be exactly the value needed for 3mA.

However the dn2540 part usually requires a higher value no?
I'm going by the datasheet and memory that the DN2540 cuts off below about 2.2 volts The official max Vgs cutoff is -3.5 volts which would require 3.5 mA through the 1K resistor. So I think you're pretty safe with 1K and the DN2540.

With the 10M45 I recall always needing a smaller resistance than the datasheet chart shows. Closer to the 10M90 spec actually...
  Reply With Quote
Old 3rd July 2012, 09:07 PM   #5
Account disabled at member's request
 
Join Date: Jul 2009
Thanks! I will start with 1k and see where that goes.
  Reply With Quote
Old 3rd July 2012, 10:32 PM   #6
Fenris is offline Fenris  United States
diyAudio Member
 
Join Date: Jun 2004
Location: The last frontier
Those devices don't work well below 10ma. For values that low, I'd use a cascoded LM134/LM334 and 10m45s or dn2540. I use Walt Jung's circuit that he used for his article on constant current sources for the LM317 and 10M45s cascode, except the physical pinout of the LM134 is reversed from the pins of the LM317. The LM134/334 datasheet has values for the Rset that are more accurate and consistent than the depletion mode MOSFETS.
__________________
Listen to the music through the stereo, not the stereo through the music.
  Reply With Quote
Old 3rd July 2012, 10:43 PM   #7
Account disabled at member's request
 
Join Date: Jul 2009
very nice. I remembered the combo from the article...just a few questions.

1) Could you please define bad? Noise rejection/reliability...?

2) why replace lm317 with lm334? The schematic shown in the article seems to be "ideal" (words of the author) Is the load too low even for lm317+dn2540?

Thanks!
  Reply With Quote
Old 3rd July 2012, 10:53 PM   #8
Account disabled at member's request
 
Join Date: Jul 2009
Also...is the stabilization R/C circuit required even with lm334 operation?
  Reply With Quote
Old 3rd July 2012, 11:16 PM   #9
Fenris is offline Fenris  United States
diyAudio Member
 
Join Date: Jun 2004
Location: The last frontier
The problem with the MOSFET alone or with the LM317 is that at low currents (less than 5-10ma) the dropout voltage becomes too low and they become either unstable or unable to keep regulation. The LM334 has a maximum of about 10ma while the LM317 has a minimum of around 5 ma. Below 5ma I use the LM334 with great success (see: New amp: 13DE7 SE hybrid). I use the stabilization network as cheap insurance - it costs little and can't hurt.
__________________
Listen to the music through the stereo, not the stereo through the music.
  Reply With Quote
Old 4th July 2012, 05:33 AM   #10
Account disabled at member's request
 
Join Date: Jul 2009
with a lm334 a good value trimpot would apparently be 100ohm. Correct?

Also in the schematic (by Jung) there is the R/C stabilization network but also a cap from B+ to ground. Could someone elaborate on that?

Thanks!
P.s. I read the thread you opened. Nice design. I for one like the mosfet in the output!
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
DN2540 + LM317 cascode CCS? rongon Tubes / Valves 11 23rd December 2012 11:25 PM
DN2540 CCS questions RollE2k Tubes / Valves 6 19th March 2012 06:12 PM
Rset values for IXYS IXTP01N100D JLH Tubes / Valves 5 7th March 2012 06:24 AM
Supertex CL2 Mikael Abdellah Parts 0 18th March 2010 01:05 PM
Help on Cascode DN2540 CCS swordsman Tubes / Valves 1 24th December 2008 04:48 AM


New To Site? Need Help?

All times are GMT. The time now is 08:12 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2