# PNP Transistor - Amateur Question

• carlodelmundo
In summary, when a voltage is applied to the base of a PNP transistor, it blocks current from passing from the emitter to the collector. Without a voltage applied to the base, current can flow freely. However, in order to have a closed circuit, a base resistor is needed to supply current to the base and turn on the collector-emitter current. PNP transistors are similar to NPN transistors, but with reversed polarity. The importance of a base resistor can be visualized by rotating the circuit so that the collector is at the top. In PNP transistors, current must be let out of the base to turn on the transistor, which happens when the base voltage is lower than the emitter voltage.
carlodelmundo
I understand that when we apply voltage to the Base of the PNP Transistor (Emitter, Base, Collector), we actually block current from passing from Emitter to Current.

If there is no voltage applied to base, then current flows freely.

If this is the case... how come when I wire the following:

1.) + terminal of battery to
2.) diode (pointing towards +) to
3.) "Emitter" of PNP Transistor
4.) The "collector" of PNP transistor goes to
5.) - terminal of battery.

I get no closed circuit? (by the way, there's a resistor and LED between 4 and 5). However, when a voltage is applied to the base (even the slightest), the current is open?

The missing component is the base resistor.
Even though this is connected to ground, it supplies current to the base of the transistor to turn on the collector-emitter current.

PNP transistors are exactly the same as NPN transistors, except that the polaraity is reversed.

So, if it helps, just rotate the circuit so that the collector is at the top. You can now see the importance of having a base resistor and where it has to go.

Yes, basically in pnp transistors, you have to let current out of the base to turn on the transistor. This occurs when the base voltage is lower than the emitter voltage.

## 1. What is a PNP transistor?

A PNP (positive-negative-positive) transistor is a type of bipolar junction transistor (BJT) that consists of three layers of doped semiconductor material. It has a p-type semiconductor sandwiched between two n-type semiconductors, hence the name PNP. It is commonly used as an amplifying or switching device in electronic circuits.

## 2. How does a PNP transistor work?

A PNP transistor works by controlling the flow of current between its collector and emitter terminals using a small current at its base terminal. When a small current is applied at the base, it allows a larger current to flow from the collector to the emitter. This makes it a useful component in electronic circuits for amplification and switching purposes.

## 3. What is the difference between a PNP and NPN transistor?

The main difference between a PNP and NPN transistor is the direction of current flow. In a PNP transistor, the current flows from the collector to the emitter, while in an NPN transistor, the current flows from the emitter to the collector. The polarity of the voltage applied to the base terminal also differs between the two types of transistors.

## 4. How do I identify the pin configuration of a PNP transistor?

The pin configuration of a PNP transistor can be identified by looking at its datasheet or by using a multimeter. The emitter terminal is typically marked with an "E" or a "-" symbol, the collector terminal with a "C" or a "+" symbol, and the base terminal with a "B". The base terminal is often placed in the middle, with the emitter and collector on either side.

## 5. Can I use a PNP transistor in place of an NPN transistor?

No, PNP and NPN transistors are not interchangeable. They have different polarities and pin configurations, which means they require different circuit designs. Using a PNP transistor in place of an NPN transistor would result in incorrect functionality or even damage to the circuit.

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