Go Back   Home > Forums > Design & Build > Parts

Parts Where to get, and how to make the best bits. PCB's, caps, transformers, etc.

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 15th December 2005, 12:04 AM   #21
Stocker is offline Stocker  United States
diyAudio Member
 
Join Date: Dec 2003
Location: Austin
What, was this in a newspaper or something? More people paying attention, wow!

Goals re: features:
Simultaneous display of Vbe Ic and Ib
Switchable current ranges for Ic
Adjustable current for Ib (currently 2 ranges)
Test NPN, PNP and N & Pch. FETs
DC testing
AC testing looking like it will make the list thanks to the recent blessing of a free O'scope (thanks, God)

Protection for the panel meters is intended to be limited by the voltage of the supply... about 12V is all it will have to give, which with the current resistors is safe for a 1.99 (or 1.999) volt meter. That is a good point though. Perhaps the circuit just got a bit more complicated, I'll have to think about it some. Currently, there are some low-noise buffers planned to isolate the test from the meters. Clamping the output shouldn't be too hard.

As for selecting Vce, it sort-of just happens with this design and I'm hard-pressed to think why I would want to monitor it, seeing it's to be a direct relationship with the Ic reading.

peranders, jackinnj has it right with my motivations for building this unit.... DIYAudio is the name of the board... matched components baby. You do raise a different point tangentially: This is not going to be a tester to determine what a device is, as I don't plan on using unknown devices in my DIY Audio kit. Datasheets only get you so far. Then we need some actual numbers

Thanks guys, keep it coming. Jackinnj I'll have to peruse that article after work.
__________________
Jesus loves you.
  Reply With Quote
Old 15th December 2005, 05:08 AM   #22
Electrons are yellow and more is better!
diyAudio Member
 
peranders's Avatar
 
Join Date: Apr 2002
Location: Göteborg, Sweden
Blog Entries: 4
Quote:
Originally posted by Stocker
peranders, jackinnj has it right with my motivations for building this unit.... DIYAudio is the name of the board... matched components baby. You do raise a different point tangentially: This is not going to be a tester to determine what a device is, as I don't plan on using unknown devices in my DIY Audio kit. Datasheets only get you so far. Then we need some actual numbers.
If you have made a good design no part have to be matched, possible the input stage. When you design you use worst case values of critical parameters. If the Hfe is 300 typical and min 150 you take 50-100 as a working value.

If you of some reason do want to match do it in the real stage. Mount a socket and change only one transistor. Note the offset (or whatever) on each transistor. Two transistors with the same offset are probably alike. Building a real transistor tester is a massive overkill. I had a curve tracer long time ago. It was very neat but it was more for checking possible broken transistors.
__________________
/Per-Anders (my first name) or P-A as my friends call me
Tube Buffered Gainclone in work |Thread || Diamond buffer |Thread for the group buy | Wiki
  Reply With Quote
Old 15th December 2005, 09:20 PM   #23
Stocker is offline Stocker  United States
diyAudio Member
 
Join Date: Dec 2003
Location: Austin
To each his own. Perhaps Pass would have a thing to say about optimal designs not requiring matched devices? There are several amplifiers I would like to build that require matching for low DC offset at the very least. Besides, aside from the effort, why *not* build it? It has already been a learning experience.
__________________
Jesus loves you.
  Reply With Quote
Old 16th December 2005, 07:08 AM   #24
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
Hi,
Peranders,
your worst case is only considering lowest gain.
For some performance specs, a worst case would be when one Q is lowest gain and the other Q is highest gain.
The spread in parameters is the problem.

Stocker,
if you see a performance improvement by matching transistors come back and report your results. I suspect it will mirror the results achieved by many others.

As an aside D. Self published measured voltages and estimated currents on an LTP front end with almost matching transistors. He particularly drew our attention to input bias current and input offset and how it flowed to the output, but could not be corrected by NFB
__________________
regards Andrew T.
  Reply With Quote
Old 18th December 2005, 06:01 AM   #25
Stocker is offline Stocker  United States
diyAudio Member
 
Join Date: Dec 2003
Location: Austin
Thanks for the encouragement guys. I stayed up and did some calculating last night; hopefully I will complete this thing within the year (note, this is the 2nd year of 'construction'! )

As for improvements, I am hoping there will be none: I aim to build my stuff one time (ha, as if it were possible) and build it as well as I can that once. You all may note from paragraph one of this post that I like to take my time... hopefully this contributes to the best result possible!

Thanks,

David
__________________
Jesus loves you.
  Reply With Quote
Old 20th December 2005, 07:13 PM   #26
diyAudio Member
 
jackinnj's Avatar
 
Join Date: Apr 2002
Location: Llanddewi Brefi, NJ
here's the Tester using the Measurement Computing USB-1208FS -- on a protoboard -- an LM317 was used to set collector current to 10mA -- for BJT's values of R can be adjusted between output and adjust to set the current from 100uA to 1A -- with the drop-down list. Sorry, I haven't yet completed the MU test for FETs.

I reworked the graphical user interface to be a lot simpler -- just press the button to switch between FET or BJT -- anyone who purchases one of these MCC devices and would like the code just send an email and I'll send a zip file back.

Click the image to open in full size.

Click the image to open in full size.
  Reply With Quote
Old 21st December 2005, 05:28 AM   #27
Stocker is offline Stocker  United States
diyAudio Member
 
Join Date: Dec 2003
Location: Austin
Hey that's pretty sweet for low current testing. Try to get 40W into an output device with it tho!
__________________
Jesus loves you.
  Reply With Quote
Old 27th December 2005, 10:34 PM   #28
anatech is offline anatech  Canada
diyAudio Moderator
 
anatech's Avatar
 
Join Date: Jun 2004
Location: Georgetown, On
Hi Stocker,
I normally use a Heathkit IT-18 for testing. Jigs for matching power transistors.

I'm watching your thread.

-Chris
  Reply With Quote
Old 27th December 2005, 11:46 PM   #29
Stocker is offline Stocker  United States
diyAudio Member
 
Join Date: Dec 2003
Location: Austin
Ah well, since you're watching, I'll update.

I have been pondering numbers and I am -->.<-- this close to putting parts together. I just need a few clear hours at a stretch with nothing else to do...with a job, wife, kids, dogs, house etc. you can see the hours are few/far between. I have been making slow progress though. The 3rd panel meter has been modified to fit the chassis. The wiring needs to be ironed out. I need to select the actual switches that I will use. I will make a temporary final schematic and wire up a test to see if the circuit is valid.

Big Brother is watching also.

Hello, Echelon.
__________________
Jesus loves you.
  Reply With Quote
Old 28th December 2005, 12:15 AM   #30
anatech is offline anatech  Canada
diyAudio Moderator
 
anatech's Avatar
 
Join Date: Jun 2004
Location: Georgetown, On
Hi Stocker,
Should be interesting to see what you end up with. Since you're a calibration tech like I was, I'll give you a list of equipment I use when you are done. It would be nice to be able to match outputs in banks instead of onesy-twosy.

-Chris
  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
2 transistor current source Omicron Parts 16 22nd February 2006 09:02 AM
LM317 with a parallel transistor for current? Progg70 Power Supplies 2 31st August 2005 05:01 PM
too much current thru transistor xplod1236 Parts 27 29th May 2004 04:09 AM
transistor tester janey Solid State 0 4th January 2002 02:44 PM


New To Site? Need Help?

All times are GMT. The time now is 07:45 AM.


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