Why match transistors?

[JoeBob]

Alright, I know that matching them is obviously the better thing to do, but my next project uses quite a few small signal transistors and I was wondering if I really have to match them all. What's the difference really between matching them and just selecting at random? Basically I'm a lazy guy and all I want to know is will **** break if I don't match them heh...

 

[peranders]

You can use BC847BS and BC857BS. They are very cheap but small. Works like separate BC847 and the matching is fair, remember the price! The big advantage is temperature matching. I have tested them in my monster overkill phono amp and they worked very well.

To answer your question: When you use differential stages and currrent mirrors it can be a good idea to match or use matched transistors but I would say it's more important to keep the temperature equal. I would also say it's more important in diff stages to match.

http://home5.swipnet.se/~w-50719/hifi/qsxm2/layout_qsxm2.html#Anchor-47857

 

[Nelson Pass]

depends on the project. With Bipolar
devices you can probably get away with
it regardless.

 

[JoeBob]

Thanks..

Ah, this is great news for a lazy guy like me, time to start building then...