QUICK QUESTION: Will both transistors pass current?

[TrevorP]

I'm just wondering if any current will go through Transistor a when its emitter is left open.

 

[Tomble]

Do you maybe mean through the collector-base diode junction thing? Because it reads as though you're asking about emitter current.

 

[TrevorP]

Yes. What I'm really asking is if that switch will change which transistor is being used? Or will I need a DPDT to change two wires at once?

 

[john1]

Yes, that should do it.

(within wkg voltages)

 

[TrevorP]

Thank You.

 

[Tomble]

Eh, I think "no" to the question of emitter current isn't quite "no" to the question of the base-collector diode I think. The latter sort of conduction may or may not be considered to be inside what john1 describes as working voltages (I'm not quite awake ATM sorry), it's not quite standard usage. It crops up IIRC when transistors go into saturation, which is at least ordinary when the emitters are conducting. Whatever. If an NPN's base is ~0.6v more positive than its collector, it conducts that way, and if a PNP's collector is ~0.6v more positive than its base, it conducts that way. Something along those lines.

Also there's the question of what sort of voltage/current those top and left terminals have. Because the diagram looks as though the top terminal would be +ve, in which case you're showing PNP transistors where you'd surely want NPN transistors- unless I'm missing something real unusual, neither transistor will pass current with grounded emitter but +ve base and collector, they'd be reverse-biased or whatever. Or blown up. In fact they might be blown up anyway as there's no resistors in sight and we haven't been told the terminals go to current sources.

Thos various things aside though, no I'm not aware of any way that the disconnected emitter could pass current.

 

[TrevorP]

ohh yeah no there will be resistors and what not I was just dealing with the transistors. It's just that I would use the switch for the Base input but as PNP's are always on it creates a problem of me wanting to turn it off.

 

[Roff]

What are you actually trying to do?

 

[TrevorP]

I was thinking of making a fuzz pedal in which you can switch between germanium and silicon transistors.

 

[Nigel Goodwin]

I was thinking of making a fuzz pedal in which you can switch between germanium and silicon transistors.

Then make two entirely seperate circuits (they are simple enough), and switch them over with a simple DPDT switch.