what happened if i give 5V directly to BC547 transistor.

[karthigowri]

hi,
I know the limitation of base voltage of transistor.but,I don't know why? please explain.

 

[BradtheRad]

The base-to-emitter is a PN junction. It behaves like a diode. It has a limit to the amount of milli-Amperes it can convey safely.

if i give 5V directly

The B-E operates in a range of a few tenths of a volt. By applying 5V it destroys the transistor because you are increasing current through the PN junction.

However suppose you apply 5V through a high resistance (say 10k). Then the transistor operates normally because current is small. Consequently B-E voltage is reduced to the normal level of a few tenths of a volt.