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Supplied to the base is under the threshold voltage amount of 0.7V, at which point the transistor no longer conducts across collector to emitter and shuts off.Ī PNP transistor functions the total opposite way.Īs current is sinked from the base (flows out from the base to ground), the transistor is on and conducts across to power on the output load.

The transistor conducts more and more current until it conductsĪnd as you decrease current to the base of a NPN transistor, the transistor conducts current across from collector to emitter less and less, When the voltage supplied to the base exceeds the threshold voltage of 0.7V, as you increase current to the base of a NPN transistor, (current flowing out of the base to ground). The positive voltage to the emitter allows current to flowįrom the emitter to the collector, given that there is negative current to the base This positive voltage to the collector allows current to flow acrossįrom the collector to emitter, given that there is a sufficient base current to turn the transistor on.Ī PNP transistor receives positive voltage at the emitter terminal.

Positive voltage is given to the collector terminal and current flows from the collector to the emitter.įor a PNP transistor, positive voltage is given to the emitter terminal and current flows from the emitter to the collector.Īn NPN transistor receives positive voltage at the collector terminal. Therefore, to produce current flow in an NPN transistor, Sandwiching a layer of N material, while NPN transistors are made up of 2 layers of N material sandwiching 1 layer PNP transistors are made up of 2 layers of P material How voltage is biased to them to produce currentįlow is different, and their current flow is opposite as well. Since PNP and NPN transistors are composed of different materials, Voltage Allocation and Current Flow are Switched In a PNP transistor, output current flows from theīelow we go over the concepts explained above in more depth, with diagrams, to better illustrate the differences between NPN and PNP transistors. In an NPN transistor, output current flows from the collector to the emitter. (current must flow out from the base to ground).Īnother concept differentiating NPN and PNP transistors is that since voltage is allocated differently, they have opposite currentįlows at the output. While a PNP requires negative current to the base So a simple approach of thinking about it is an NPN transistor requires positive current to the base, This means current needs to flow out of the base. In a PNP transistor, current is sourced away or sinked from the base of This means current needs to flow into the base. So knowing this, with an NPN transistor, current needs to be sourced to the base of the transistor for operation. As long as the voltage at the base terminal is lower than at the emitter terminal in a PNP transistor, the correct biasing and negative current In a PNP transistor, current flows out of the base (negative current to the base) by giving the base terminal a more negative (a lower) Therefore, the base of an NPN transistor must be connected to positive voltage for current toįlow into the base. On when a sufficient current is supplied to the base of the transistor. Since voltage allocation is different, how current flow works to turn them on is different. Transistor receives positive voltage to the emitter terminal and a negative voltage at the base terminal (or rather a more negative or lower voltage than what is supplied at the emitter terminal). An NPN transistor receives positive voltage to the collector terminal and positive voltage to the base terminal for proper operation. Must be allocated differently in order for them to work. Since they are internally constructed very differently, How they differ is how power must be allocated to the terminal pins for them to provide this amplification or So technically, they achieve and do the same exact thing. NPN and PNPs are exactly the same in their function, they provide amplification and/or switching capability. BJTs are current-controlled transistors that allow for current amplification.Īllows for a much larger current across the emitter and collector leads. Difference Between an NPN and a PNP Transistorīefore we talk about the differences between NPN and PNP transistors, we will first discuss what they are and their similarities.īoth NPN and PNP are bipolar junction transistors (BJTs).