3904/3906 tranny specs

[Rob]

Rene Schmitz wrote:
> 
> At 15:15 04.01.99 -0600, you wrote:
> >Just wondering if it is possible to overdrive a transistor circuit to
> >the point that it burns up the transistor.
> >The synth uses 3904/3906s...
> >I am not exceeding Vc of the circuit..
> >Is there max Vbe?
> 
> Not exactly but base current raises exponentially with Vbe. I think it is
> possible to burn trannies by exceeding their base current if theres no
> emmiter resistor, or base resistor.
> 
> Btw. For what purpose do you want to burn them ;-)

Ahh, i was bored and I figured "Hey, I got a lot of these laying around,
lets make some  fire!" I watched that old 60's video "Fire" by that guy
and his mad world..' i am the god of hell and fire and I bring you:
3904s!! :)
sung amidst a breadboard full of burning 3904s whilst you pretend to
lick the flames..

No, honestly, I have a circuit in one of my synths that takes 5v and
converts it to 12v using 3904s trannies. BUT, i want to manipulate the
data with 4000 series cmos chips.. I want to run these off of the 12v
supply cuz they have better noise rejection @12v (and since there is
very critical circuits on the 5v supply, like the d/a converters that go
to the oscillator CVs) so I cant use the 5v supply.
> 
> >Since I am using the transistors as switches, I wouldnt think Vbe=Vc as
> >being a problem.
> 
> Actually in a switch application Vbe might exeed Vc which is about 0.1-0.2V
> for the
> switch fully on.
> 

Oh, ok.. then, if I add a series resistance to the 12v output of my
cmos, then that should limit the current enough to not cause a problem.. 
Its the voltage isnt the problem, the current is..
heh, I should have paid more attention in my discrete semiconductors
class.. :)

Rob