Need medium-power transistor recommendations - diyAudio
Go Back   Home > Forums > Amplifiers > Solid State

Solid State Talk all about solid state amplification.

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 20th December 2007, 06:54 AM   #1
Account Disabled
 
Join Date: Jan 2006
Location: whereisit
Question Need medium-power transistor recommendations

I want to build a Hawksford I/V for AD1955, a DAC that puts out 8.4 mA (plus bias). I find power dissipation is simply too high for the usual 2SA970/2SC2240 if I raise voltage enough to get them into a reasonable operating point with that kind of current from the DAC. So I need recommendations for medium power BJTs that are similarly linear (or better if such are around, of course) for audio use, and also have a high fT, like 100 MHz.
  Reply With Quote
Old 20th December 2007, 07:35 AM   #2
roender is offline roender  Romania
diyAudio Member
 
roender's Avatar
 
Join Date: Sep 2006
2sc3423
2sa1360
  Reply With Quote
Old 20th December 2007, 08:18 AM   #3
Account Disabled
 
Join Date: Jan 2006
Location: whereisit
Interesting. I'll try them. Not sure what effect the lower hFE will have exactly. There are no noise specs in the datasheet :|

I/V: Fig.4-4 in http://www.essex.ac.uk/dces/research...0amplifier.pdf
  Reply With Quote
Old 20th December 2007, 12:41 PM   #4
SunRa is offline SunRa  Romania
diyAudio Member
 
Join Date: Aug 2004
Location: Romania
Hello Abzug,

thank you for posting the AES paper, I was looking for some time for this.

@roender,

I didn't had the chance to congratulate you for your project. It's a great sample of design and enginering; and the thread it's a great learning source!

Am avut un sentiment de mandrie sa vad reactiile celor de pe DIYAudio la un produs romanesc!
  Reply With Quote
Old 20th December 2007, 02:46 PM   #5
Account Disabled
 
Join Date: Jan 2006
Location: whereisit
With the 2SA970/2SC2240, removing bias from the DAC output and cutting current by half, then doubling degeneration resistors and halving the feedback resistor, I get 1 kHz THD at around 1 ppm (though it goes higher at 20 kHz).

There are various problems with this I/V, including the fact that it defeats steep lowpass filters and limits their attenuation, and is unstable with some filters as well.

I think with medium power transistors and less degeneration it should be possible to get headphone-level voltage without the need for additional voltage gain, just a buffer. Also, improving some of the current sources seems to improve THD in the simulation.
  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
Pioneer Series 20 Ring emitter transistor recommendations needed brothelthug Parts 5 17th May 2006 02:01 AM
Transistor and MOSFET recommendations? meretrix Parts 2 24th January 2005 12:45 PM
TOSHIBA 2SC4793 and 2SA1837 medium power transistor pspice models? mikek Solid State 1 24th September 2002 09:14 AM


New To Site? Need Help?

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