Electronics > Beginners
Help Understanding PNP transistors
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AngraMelo:
Hello guys,
I have been studying the theory and the practical side of electronics for a while. As Im doing everything on my own, I have large knowledge gaps spread out on different levels.
When I see explanations about transistor, they almost always use the NPN type to explain saturation, Vce and general calculations.
So I ended up having a lot of PNP theory to study and understand (the negative voltages and everything makes it harder for me)

When Im calculating the power dissipation of a transistor, I assume the formula is: P= (Vce)x(Ie)
So I know that if I put 10V at the base of a NPN, and its collector is at 20V, ill get around 11Vce.

How does that work for a PNP? is it exactly the same?
So if I have the emitter at 20V and I apply 10V to the base I will get Vec = 11V?
eev_carl:
If you're talking about a common emitter, you may want to check out this recent thread.  It's on NPN, but the forum warned me about putting 1V at the base.  I imagine they'd have a problem with 10V as you'd need even more resistance (100k?) to produce the microamps of Ib.

https://www.eevblog.com/forum/beginners/question-on-npn-logic-inverter-from-textbook/

AngraMelo:
My case is only theoretical, but just for reference I was thinking about big power transistors.

Thank you for your input!
Audioguru again:
The forward Vbe bias voltage of a transistor is 0.6V for low currents and is maybe 1.5V for high currents. If the emitter of a PNP transistor is at +20V then its emitter will also be +20V when the transistor is turned off and the base will be at +18.5V to +19.4V when it is turned on.
langwadt:
just flip everything up side down
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