12/24/2023 0 Comments Transistor![]() The operation of a PNP transistor can be explained by having a look at the following figure, in which emitter-base junction is forward biased and collector-base junction is reverse biased. The direction of current indicated in the circuits above, also called as the Conventional Current, is the movement of hole current which is opposite to the electron current. A small forward bias is sufficient at the emitter junction whereas a high reverse bias has to be applied at the collector junction. The collector base junction is reverse biased and its resistance is a bit higher. The N-type material is provided positive supply and P-type material is given negative supply to make the circuit Reverse bias.īy applying the power, the emitter base junction is always forward biased as the emitter resistance is very small. The N-type material is provided negative supply and P-type material is given positive supply to make the circuit Forward bias. The figure below shows how a transistor is biased.īy having a look at the above figure, it is understood that The function of both the PN junctions is controlled by providing bias to the circuit through some dc supply. As one junction is between the emitter and base, that is called as Emitter-Base junction and likewise, the other is Collector-Base junction.īiasing is controlling the operation of the circuit by providing power supply. Transistor BiasingĪs we know that a transistor is a combination of two diodes, we have two junctions here. We have so far discussed the constructional details of a transistor, but to understand the operation of a transistor, first we need to know about the biasing. The following image shows how different practical transistors look like. The PNP and NPN transistors can be differentiated using a Multimeter. In a Practical transistor, there is a notch present near the emitter lead for identification. Hence the terminals are always to be kept in mind while using a transistor. Due to the specific functions of emitter and collector, they are not interchangeable. As the collector of a transistor has to dissipate much greater power, it is made large. The arrow-head in the above figures indicated the emitter of a transistor. The symbols of PNP and NPN transistors are as shown below. This is a bit larger in size than emitter and base. Its name implies its function of collecting the carriers. The right side material in the above figure can be understood as a Collector. Its main function is to pass the majority carriers from the emitter to the collector. ![]() ![]() The middle material in the above figure is the Base. This is simply indicated with the letter E. either electrons or holes.Īs this emits electrons, it is called as an Emitter. This has a moderate size and is heavily doped as its main function is to supply a number of majority carriers, i.e. The left-hand side of the above shown structure can be understood as Emitter. They have their functionality as discussed below. The three terminals drawn from the transistor indicate Emitter, Base and Collector terminals. The following illustration shows the basic construction of transistors They are PNP and NPN which means an N-type material between two Ptypes and the other is a P-type material between two N-types respectively. This type of connection offers two types of transistors. Three terminals are drawn out of the three semiconductor materials present in it. The Transistor is a three terminal solid state device which is formed by connecting two diodes back to back. It also regulates the incoming current and voltage of the signals. Uses of a transistorĪ transistor acts as an Amplifier, where the signal strength has to be increased.Ī transistor also acts as a switch to choose between available options. Such a formation is simply called as a Transistor.Ī Transistor is a three terminal semiconductor device that regulates current or voltage flow and acts as a switch or gate for signals. If another P-type material or N-type material is added to a single PN junction, another junction will be formed. Emitter Follower & Darlington AmplifierĪfter knowing the details about a single PN junction, or simply a diode, let us try to go for the two PN junction connection.Transformer Coupled Class A Power Amplifier.
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