Phantom regulator - replacement for BC546?

[audiox]

A replacement for BC546 but with higher CE voltage? Cheap and widely available if possible. Or better but still simple phantom regulator circuit?

The circuit I use is very simple single transistor regulator. Collector is input, 10K resistor from collector to base, 47V zener from base to ground and emitter is output. Only three components if capacitors are not included. Works fine untill output is shorted to ground (less than one second is enough and transistor is dead!). I guess it is too high CE voltage that kills the transistor.

 

[jdbakker]

I'd expect a short would violate Ic(max) not Vce(max) (which, on a BC546, is 65V), especially with a bulk electrolytic capacitor on the input (collector) side. A fix to this would be a current limiting resistor in the collector lead; I'd say around 100 Ohm for a P48 regulator. Two diodes in series between B and E, or a 1k resistor in the B lead will protect you from base breakdown if there happens to be a (large) decoupling cap directly tied to the base (at the expense of regulation accuracy and a small amount of output noise).

How high is the input voltage ? What is the capacitance on the input/output side ?

JDB.

 

[audiox]

Thanks. You are probably right. There is not much space on PCB so 100ohm collector resistor is the only true alternative. Hope it doesn't affect regulator stability. Input and output caps are both 10u. There is also 10u base cap for improved noise.

 

[bcarso]

Since the collector is rather high impedance already a series R would have little effect---in fact it might enhance stability in cases where the emitter has significant reactive loading.

Of course the protection afforded will be of short duration, but enough to allow survival of a brief accident.