what is a 'leaky' transistor?

[loonatron]

I'm trying to read a book about servicing audio gear, and the author keeps using the slang word "leaky" when describing the condition of transistors, IC's, diodes, triacs, etc... Does he mean that they are leaking current when they shouldn't be? He also says things like "a burnt resistor could be the result of a leaky transistor or IC"

thanks, from Steve

 

[Frank Berry]

"Does he mean that they are leaking current when they shouldn't be?"

Absolutely correct, sir.

 

[loonatron]

Thanks Frank!

Would a transistor be more likely to 'leak' across the pins that it's normal function allows current to flow, i.e. stay turned on, reguardless of the base potential? Is it less likely to 'leak' between the base and the other pins?

...Steve

 

[Frank Berry]

A transistor can develop "leaks" between any (or all) pins.
If the transistor begins to "leak" current between the collector and the base, the transistor will self-bias itself on. If the "leak" is between the emitter and the base, it will be more difficult to drive into conduction.
Worse case is a leak between collector and emitter. At that point, you have a wire rather than a transistor.

 

[jan.didden]

Normally leaking occurs across reverse biased junctions, like leakage currrent across the C-B diode junction, leading to base current, leading to collector-emitter current. If you reverse-bias the B-E junction, you will see a sudden jump in (leakage) current at around 7V. That is why you can use a reversed B-E as a zener.

Jan Didden

 

[peranders]

All switching parts leak by nature by the can show increased leakage if they are damaged by age, overload (secondary breakdown), ESD etc.

 

[jan.didden]

[snip]....damaged by age, overload (secondary breakdown), ESD etc.

P-A, are you talking about yourself??

Jan Didden

 

[loonatron]

Many thanks for those replies!

I will have to think about janneman's post tomorrow though! (too tired to think)

 

[teemuk]

I encountered the similar leaking problem. It seems to be voltage related. The transistor can leak from collector to emitter if it´s operating near it´s maximum voltage value.