Confused over hfe variation in BC559 transistors - diyAudio
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 31st August 2002, 07:46 PM   #1
Beggar is offline Beggar  United Kingdom
diyAudio Member
 
Beggar's Avatar
 
Join Date: Aug 2001
Location: South East, UK
Default Confused over hfe variation in BC559 transistors

Hi everyone, im trying to put together a mic preamp P93 of Mr Elliott's and have found a large variation in the hfe of 3 of my transistors, 70, 100 and 140, all apparently BC559. Im not very good (at all) at transistor electronics, and have no idea what the implications of this are (if any), does this actually make any difference?

Sorry for this lame question, any responses would be cool.
  Reply With Quote
Old 31st August 2002, 10:51 PM   #2
diyAudio Member
 
Join Date: Jan 2001
Location: Scandinavia
Due to the physics involved you will find very large variations in HFE and (Hfe which is the small signal equivalent we usually hope is the same as the DC version which you likely measured) in bipolar junction transistors.

For the same reason, the Vbe is without significant variation.

Conversely you will find that for FET's, the Vgs (Vbe equivalent) is extremely variable (usually say 3.5-4.5V).

Tubes are usually pretty damn close in tolerance.

Petter
  Reply With Quote
Old 1st September 2002, 01:08 AM   #3
diyAudio Member
 
kiwi_abroad's Avatar
 
Join Date: Sep 2001
Location: Wellington, New Zealand
I havn't looked at the circuit you mentioned, but most, if not all circuits using BJT's are designed to not be influenced by hfe variations.
If you think about it, even if you did get a pair with identical hfe values, those values change with collector current, Vce voltage, temperature, frequency, time, lunar cycles etc. and they will diverge.
  Reply With Quote
Old 1st September 2002, 01:09 AM   #4
diyAudio Member
 
Tube_Dude's Avatar
 
Join Date: Mar 2002
Location: Aveiro-Portugal
Default beggar

The BC559 may have a a hfe betwen 125-475.

But if you need nmore acuracy in hfe you can use:

BC 559 A------hfe-125-250

BC 559 B------hfe-220-475

choosing the A or the B you have less variation of hfe...


Regards


Jorge
  Reply With Quote
Old 1st September 2002, 03:54 PM   #5
Beggar is offline Beggar  United Kingdom
diyAudio Member
 
Beggar's Avatar
 
Join Date: Aug 2001
Location: South East, UK
ok thanks for your replies everyone, i can get on with building my preamp now!
  Reply With Quote
Old 29th September 2002, 06:13 AM   #6
Electrons are yellow and more is better!
diyAudio Member
 
peranders's Avatar
 
Join Date: Apr 2002
Location: Göteborg, Sweden
Blog Entries: 4
Default Re: Confused over hfe variation in BC559 transistors

Quote:
Originally posted by Beggar
Hi everyone, im trying to put together a mic preamp P93 of Mr Elliott's and have found a large variation...

Sorry for this lame question, any responses would be cool.
Note also that BCxxx have different data from different manufacturers. I noticed that when I did some research about noise and caps in BC560C and BC550C. Frankly everything is different, speed also! At the moment ON semiconductors seems to have the best BCxxx types.
__________________
/Per-Anders (my first name) or P-A as my friends call me
Super Regulator SSR03 Group buy
  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
ONO variation for AX Tyimo Pass Labs 8 3rd March 2007 10:10 AM
DC offset variation. Nuuk Chip Amps 40 9th February 2005 03:54 PM
BC559/549 - brand? sobazz Solid State 0 5th February 2004 01:11 PM
BC549/BC559 Needed Cambe Parts 2 26th January 2004 10:40 PM
zen variation 2 Antonello Pass Labs 1 23rd July 2002 10:07 PM


New To Site? Need Help?

All times are GMT. The time now is 03:18 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright İ1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2