Piletid vastustega
In power electronic circuits bipolar
NPN are more common than PNP.The base thickness must be made as small as possible in
order to have a high amplification effect, but too small base thickness will reduce the
breakdown voltage capability.The allowed max voltage UCE between the collector and the
emitter depends slightly on the base current.Since the current gain of power bipolar
transistors is small, two transistors are usually connected as a pair.It's called Darglington
transistors.The emitter of the first transistor is connected to the base of the second one.A
connected pair of bipolar transistors could raise the current gain of a power device.The
difference between power and low current transistors is, that power transistors have primary
and secondary breakdown area in output characteristics.After primary breakdown, the
transistor can operate, but the secondary breakdown destroys the transistor completely.As a
annaabi.ee 
