|
ideal transistor is perfect isolant until you
Source current into the base of npn transistor or
Drain current from base of pnp.
in case of NPN, E-B is basically diode so you have to apply positive voltage above ~0.7V and transistors opens. In case of PNP is it simmilar just apply negative voltage to E-B. Remember, current has to flow in direction of arrows.
When you apply 1mA to base of npn with hFE 100, transistor opens and is capable to handle up to 100mA. You can multiply hFE connecting transistor into darlington circuit when current to one npn transistors base is sourced from another transistors emmiter, shown in circuit on right side.
Top left circuit shows that bipolar transistors are all about current, therefore you can connect 100V to collector (refer to datasheet first) and transistor will not pass anymore than Ie=Ib+(hFE x Ib), therefore voltage drop across C-E will be in this case 98V, and when you multiply it with 30mA which flows through transistor, youll get not much less than 3W of heat, which will successfuly destroy transistor w/o any heatsink.
|
