pnp answer
pnp and npn transistor
diff. between npn and pnp transristor
NPN and PNP are transistor types. The difference in the way the layers of semiconductor material are doped with impurities.
BT169 is neither an NPN nor a PNP transistor. BT169 is a thyristor, otherwise known as a silicon controlled rectifier.
NPN, PNP only classified to BJT, while FET classified as P-channel , N-channel
You can use a PNP or an NPN transistor in a fire alarm circuit. Both will work. It all depends on how you want to energize the alarm, and with what polarity of signal.
pnp
Switching is faster in NPN transistor than PNP. Because movement of electrons is faster than holes.
no
PNP is sourcing. NPN is sinking. You generally connect NPN to ground and your PLC(or any load)input. With PNP you connect to V+ and to your PLC. Your PLC (load) should have the same ground or V+. Sourcing (PNP) provides a path to +24DC generally. Sinking (NPN) provides a path to 0V DC.
To save a decoupling capacitor & biasing resistors for the PNP.