Electronic Design Software

While design an electronic systems, when to use PNP transistor? When to use NPN transistor?

some time I see in schematic diagram, they use PNP transistor some time use NPN. Really don't understand. Is PNP save more power?

Public Comments

1. PNP will only function when you apply a negative voltage to the base, NPN will work when a positive voltage is applied to the base.
2. It's all a matter of choice. In some cases you want a push-pull system. Then it's not so much a matter of choice. You have to choose a polarity. Do you want positive ground or negative ground? The rest chooses the type of transistor.
3. If you have a choice use an NPN, they perform slightly better than PNP in general. Less leakage current, higher power and gain.
4. NPN transistors are most commonly used in electronic circuits because the charge carriers are electrons in NPN. Hence, more conductivity is achieved in NPN transistors. PNP transistors are rarely used because of the invertion of polarity.For making forward bias,the PNP transistor should have a negative voltage at the base with respect to the emitter.In most electronic circuits,this condition is not available and also may affect another circuit parameters.So, PNP is avoided in most cases unless specified