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Topic: Transistor Leakage PLEASE HELP (Read 836 times) previous topic - next topic

surefanatic

Thanks for all the responses.

I have the same circuit except it's connected to 24V on the output instead of ground.  I switched the input of the module I was connecting to from a "ground-switching input" to a "voltage switching input"

and it works fine.

That being said i do need to figure out whats wrong with grounding circuit.


Boffin1

A high value ( 100k) resistor between base and emitter is always a good idea on a switching transistor so that the transistor doesn't amplify its' own leakage.
With my mobile phone I can call people and talk to them -  how smart can you get ?

Grumpy_Mike

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so that the transistor doesn't amplify its' own leakage.

I think not.
It is a switching transistor, it will not switch until the base voltage exceeds 0.7v. Leakage refers to current not voltage in this context.

Boffin1

but we don't really know what dc path he has on the base, there used to be a saying in the old days " don't forget the base emitter resistor"
I have solved many a bad design problem over the years by fitting the resistor.

With my mobile phone I can call people and talk to them -  how smart can you get ?

Grumpy_Mike

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there used to be a saying in the old days

Yes that was when transistors were made from germanium, nowadays they are made from silicon so that's why no one uses it any more.

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