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DIY Stompboxes => Building your own stompbox => Topic started by: Alpha579 on August 20, 2004, 04:50:28 PM

Title: Darlington Transistors
Post by: Alpha579 on August 20, 2004, 04:50:28 PM
Hi everyone,
Is there any reason against using Darlington transistors in boosts or overdrives? Like noise or interference?
Thanxs,
Alex
Title: Darlington Transistors
Post by: Hal on August 20, 2004, 08:09:18 PM
eh...some are noisey.  Socket and try.  I played around with them in a multiface, and they sounded good for some stuff, but it was _too much_ gain.  Like...it was a fizzy, high trebleish sound.  

But hear it for yourself.
Title: Darlington Transistors
Post by: freebird1127 on August 21, 2004, 12:59:21 AM
The thing about Darlingtons is that they are essentially two transistors in one.  They are configured in such a way that the darlington's Beta value can be found by multiplying the individual Beta values of each transistor...

Beta * Base Current = Collector Current.  If a typical BJT has Beta of 100, the Base Current times 100 will calculate the collector current at that moment in time.  

If we use 2 of these BJTs to construct the Darlington, it's Beta value would be 10,000, which isn't at all unrealistic.  Base Current times 10,000 is, of course, a much higher collector current, and would probably reach the saturation limit set by the collector resistor.

Essentially, this means that the Darlington is prone to clipping much harder than a single BJT.  

I think that for most circuits, you can swap a Darlington in where a BJT was and it will work to some extent, never tried it tho...

Take care!