Whilst reading about differences between PNP and NPN transistors I came across the following circuit diagrams:
http://www.learningaboutelectronics.com/Articles/Difference-between-a-NPN-and-a-PNP-transistor
The uppermost circuit diagram, illustrating the function of the NPN transistor, shows the load positioned before the transistor.
The lowermost circuit diagram, illustrating the function of the PNP shows the load positioned after the transistor.
Would anybody be kind enough to advise if this is significant and a function of the type of transistor. My understanding would be that the behaviour of the load would remain the same, regardless of its position before or after the transistor.
Thanks
Best Answer
What do you mean by "before the transistor" and "after the transistor"?
In both cases shown, the load is connected to the collector of the transistor. The circuits may look different, because an NPN and PNP transistors work with opposite polarity power supplies.
An NPN transistor works with the emitter as the most negative terminal, and the collector positive, while a PNP transistor wants the emitter to be the most positive terminal, and the collector most negative.
If you have a simple NPN circuit, you can change the transistor to PNP and invert the power supply polariity, and the circuit should still work.