The Collector region collects most of all charge carriers emitted from the Emitter. But, the width of the middle layer is very small and it is lightly doped. So, Base voltage is a minimum of 0.7 V in reverse bias to conduct the transistor.It means that, if the Base voltage is zero or less than 0.7 V, the current cannot flow and it acts as an open circuit.To turn ON the transistor, the Base voltage must more than 0.7 V. In this condition, the transistor acts as a close switch.The main differences when comparing PNP transistors vs NPN transistors have been summarized in the table below:Electrical4U is dedicated to the teaching and sharing of all things related to electrical and electronics engineering.We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites. Working of NPN Transistor. So, it is necessary to give a voltage source in reverse bias more than 0.7 V.In general, when the switch is OFF, the current cannot flow and behaves as an open circuit. This post provides a detailed information about PNP Transistor, how PNP transistor works, its characteristics, applications, advantages and disadvantages.A PNP Transistor is a type of Bipolar Junction Transistor which is composed of three layers where ‘N’ doped layer is sandwiched between two ‘P’ doped layers. In this bipolar junction transistor, the voltage across the emitter-base junction (that is in forward-bias) is always less than the collector-base junction (reversed-bias). Click here to see our privacy policy.
It also implies that reducing forward bias voltage decreases the current flow.The relationship between DC currents and voltages are represented graphically, which are known as characteristics. The emitter-base junction is connected in forward biased due to which the emitter pushes the holes in the base region. PNP transistor works same as NPN for a switching operation, but the current flows from the base. Working of PNP Transistors: As discussed above, the transistor is a current controlled device which has two depletion layers with specific barrier potential required to diffuse the depletion layer. transistor, then here the polarity and direction of current are reversed.If a PNP transistor is connected with voltage sources as shown in the above figure, the base current will flow through the transistor.
The left P-type layer works as an Emitter terminal (E) and the right P-type layer works as a Collector terminal (C).The Emitter and Collector (P-type) layers are heavily doped compared to the Base (N-type) layer. Electrons travel slowly in a semiconductor and holes move more slowly than electrons. While the Collector-Base junction is in reverse bias and hence the depletion region at Collector-Base junction is wide.The Emitter-base junction is in forward bias. P type semiconductor contains holes and This holes going to transfer to the base. This allows more carriers to reach the Collector which in turn increases the current flow from Emitter to Collector. similarly, when the switch is ON, the current will flow through the circuit and act as a close circuit.The transistor is nothing but a power electronics switch that can work like normal switches. Therefore, a very large number of holes from emitter cross the depletion region and enter the Base. PNP transistor works when the emitter-base junction is forward biased while collector-base junction is reverse biased. This means that the Base is at higher potential than the Collector. In PNP Transistors the electrons are minority charge carriers and holes are majority charge carriers. The emitter-base diode is connected in the forward-bias, whereas the collector-base diode is connected in the reversed-bias. 2 – PNP Transistor Symbol.
PNP Transistor is a sub-type of Bipolar Junction Transistors (BJT’s). But The number of electrons in the Base is very small because it is a very lightly doped and thin region. The base of the transistor is thin and very lightly doped.
Simultaneously, very few electrons enter in Emitter from the base and recombine with the holes.The loss of holes in the emitter is equal to the number of electrons present in the Base layer. As we have seen in the working of the PNP transistor, if the Base voltage is not more negative then Emitter voltage, the current cannot flow through the device. Pnp transistor working – In the above figure shows the basic connection of pnp transistor. Only a few donor or acceptor atoms are required to produce changes in the resistivity of a semiconductor.PNP Transistor works when Base Emitter junction is The Base Collector region is reverse biased which uses external voltage source. In PNP transistor circuit, the base is always negatively biased with respect to the emitter and this type of switching is used for negative ground configuration.