Choices for Vas transistor - Page 4 - 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 4th May 2005, 12:56 AM   #31
Account Disabled
 
Join Date: Aug 2004
Location: Earth
Hey
kimschips - just as added miller Cdom capacitance is used to slug down the GBW of the Vas to establish the dominant pole which also degrades PSRR to the supply that the Vas input is referenced to,... so too with the intrinsic Ccb of the device which sets the upper limit. intuitivey a device with 1pF is better than one with 2pF.
  Reply With Quote
Old 4th May 2005, 05:21 AM   #32
diyAudio Member
 
Join Date: Jun 2004
Location: Knoxville
If the rest of the circuit is made for it, what is wrong with designing the VAS Iq around 1-2mA? Then small, Lo Noise devices like FJV992 (& FJV1845) can come into play, particularly the 'E' gain series, Beta 400-800! Fairly linear gain up to 6 or 7mA. I am playing with a circuit that uses reg. +/- 60V with this device as the VAS sourced with the FJV1845 mostly out of curiosity, well when I am at home...I work out of state. I'm in Utah right now...nice scenery. A bit different from east Tennessee.

Anyway for most Applications under 10mA, also current sources, I think these could be useful devices and they are cheap and small. (SOT-23) As a VAS, I'm not totally convinced, but it does sound pretty good. I have yet to do "experiments" though to see what it will do in this application. Any thoughts?

http://www.fairchildsemi.com/ds/FJ/FJV992.pdf
  Reply With Quote
Old 4th May 2005, 03:44 PM   #33
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
Hi,
that FJV992 has adequate Vce0, mediocre capacitance, poor current, poor power and poor fT specs. It appears that fairchild have sacrificed most to achieve very high gain. There must be a better way?
__________________
regards Andrew T.
  Reply With Quote
Old 4th May 2005, 09:58 PM   #34
diyAudio Member
 
Join Date: Dec 2004
Location: Denmark
Hey

Now if we are in for smd:

www.Infinion.com

BFN 18-19
BFN 24-26
BFN 38-39

Rohm 2SC3906 2SA1514

BCP53-56

Best regards
  Reply With Quote
Old 4th May 2005, 10:37 PM   #35
mikeks is offline mikeks  United Kingdom
Account Disabled
 
Join Date: Jun 2004
Location: Animal farm
Default Re: Choices for Vas transistor

Quote:
Originally posted by Shaun
Choices for Vas transistorRegards
Shaun
http://www.zetex.co.uk/3.0/pdf/ZTX1056A.pdf
  Reply With Quote
Old 12th May 2005, 05:25 PM   #36
diyAudio Member
 
LineSource's Avatar
 
Join Date: Sep 2003
Location: SiliconValley
Default VAS for +/- 15V supplies

I would appreciate recommendations for a 1 watt complementary pair of VAS transistors for a +/- 15 V power supply. I was hoping that the lower voltage would yield some better specs.

I am currently using BD549C and BD559C in a VAS and Diamond Buffer, but they are only 500mw.
  Reply With Quote
Old 12th May 2005, 05:56 PM   #37
diyAudio Member
 
jan.didden's Avatar
 
Join Date: May 2002
Location: Great City of Turnhout, Belgium
Blog Entries: 7
... BD135/136 or 137/138?

Jan Didden
__________________
If you don't change your beliefs, your life will be like this forever. Is that good news? - W S Maugham
Check out Linear Audio!
  Reply With Quote
Old 13th May 2005, 05:33 AM   #38
diyAudio Member
 
Join Date: Dec 2004
Location: Denmark
Hey Linesource

Here is some off my favorite transistors:

2SA1540E
2SC3955E

2SA1405E
2SC3599E

2SC3601E
2SA1407E

I think you like them if low capitance, very linear hfe and 1.2W disspation without heatsink is desired

Anyone got a schematic or idea for a preamplifier with nonfeedback, 6dB gain and symmetrical circuit?
And off course very god soundquality.

Best regards
Kim
  Reply With Quote
Old 17th May 2005, 07:59 AM   #39
diyAudio Member
 
Join Date: Dec 2004
Location: Denmark
Default got new transistors!

Hello

As I said erlier I write when I got new transistors

2SA1540E
2SC3955E

From http://www.heldt-electronic.de/

Just mail them your order and send them money by Iban and switchcode.

2SA1405E
2SC3599E

From Jørgen P in denmark TLF +4544945244

Don´t know about paying them from another country, should be not be any problem.

Heldt send me MJE350 instead off 2SA1407E yuk!
Could not get 2SC3601E

Jørgen P could only get 2SC3601E and not 2SA1407E
2SA1407 can optains in another Hfe ranking

Best regards
Kim
  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
Can bias transistor mount on top(body) of output transistor?? Leolabs Solid State 23 16th February 2008 12:35 AM
various t-amp ps choices svgsnd Class D 2 28th February 2006 02:14 AM
tell me the best of three bad choices... chipco3434 Digital Source 10 23rd April 2004 09:09 AM
Home Theater Combo - choices choices smithsonga Multi-Way 1 2nd April 2003 05:11 AM


New To Site? Need Help?

All times are GMT. The time now is 12:37 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