Switching Transistors

Started by Isaiah, July 06, 2007, 11:09:03 AM

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Isaiah

Ok, so I have a circuit where I want to be able to choose between an overdriven Ge or Si Q.
But I only have DPDT switches.

Both of the transistors are PNP.
The Base of each one will definitely attached to the switch, but should I make the Collectors or Emitters switchable?
Will leaving just an Emitter or Collector attached to the E or C of another make much difference?
The Base of each transistor has a resistor to ground (different values for Ge and Si transistors), so that's why I plan
to make the Bases switchable.

Am I making much sense?

Thanks for any help :)

Alex

DWBH

I think using a 3PDT is the best way to go.

Sir H C

I am thinking if you switched the collector and emitter in/out and left the bases attached you would do the best.  With only the base attached, you have some more cap on the input, but there is not current path if the collector and emitter are floating.

Isaiah

Unfortunately I can't find a 3PDT that's suitable and I really want to get this pedal finished for a show in 2 weeks,
so ordering one isn't an option.

I can't have the Bases tied like that because each one (Ge and Si) needs a different value resistor to ground.
Surely having the Bases and either Collectors or Emitters floating/switchable would be ok... Wouldn't it?  :icon_confused:

Thanks for the help so far!

Sir H C

In that case, float the emitters.  Since this will keep things unbiased when not on (assuming the resistor from the base is always there).