And each of them has two structural forms, NPN and PNP, but the most commonly used are silicon NPN and PNP transistors
Due to the thinness of the base region and the reverse bias of the collector junction
Figure 2 (b) shows the input characteristic curve of the transistor,
germanium transistor is about 10 microamperes.
When the collector emitter reverse current Iceo (penetration current) is open at the base (Ib=0),
The cut-off frequencies f β and f α are 0.707 times the frequency when β drops to low frequency
