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DIY Stompboxes => Building your own stompbox => Topic started by: BassWombat on May 17, 2004, 02:07:09 AM

Title: Another dumb(?) question: Transistor gain?
Post by: BassWombat on May 17, 2004, 02:07:09 AM
QuoteI've chosen to use a pair of nice BC109C transistors that I ordered from Steve Daniels of Small Bear Electronics a while back. For Q1 I chose a unit with a gain of 400, and for Q2 I chose one with a gain of 388.

The above is from the Axis Wah article at Fuzz Central.

The bit I don't understand is the different gains. I've found BC109C transistors, but how do the different gain values come into play? Are they different transistors?

Excuse me if I'm missing something here - but I'm a complete newb (and I guess if you don't ask you'll never learn!)

Thanks!
Title: Another dumb(?) question: Transistor gain?
Post by: puretube on May 17, 2004, 03:01:22 AM
some help here? :
http://www.diystompboxes.com/sboxforum/viewtopic.php?t=21746
Title: Another dumb(?) question: Transistor gain?
Post by: freebird1127 on May 17, 2004, 03:09:36 AM
There is a property inherent to all transistors called their hfe or beta value (same thing, essentially).  These values can fluctuate quite a bit depending on the transistor, even within the same part number.  The current gain of a transistor amplifier is largely defined by this beta value, the actual formula being Beta x Base Current = Collector Current.  I assume this is the gain he's talking about.  I could be wrong on that, of course... someone feel free to correct me, svp...