12/12/2023 0 Comments Emitter base voltageTherefore, the transistor is completely in OFF condition. These parameters cause a large depletion layer, which further doesn’t allow current to flow through the transistor. In the below figure, the cutoff region has the operating conditions when the output collector current is zero, zero base input current and maximum collector voltage. The below figure shows the output characteristics of a BJT. Saturation Region is also primarily used in switching and digital logic circuits. In this mode, the transistor is fully switched ON and is essentially a close circuit. Current flows freely from collector to emitter with almost zero resistance. In this mode of operation, both the emitter-base and collector-base junctions are forward biased. BJT in this mode is switched OFF and is essentially an open circuit.Ĭutoff Region is primarily used in switching and digital logic circuits. As both the PN Junctions are reverse biased, there is almost no current flow except small leakage currents (usually in the order of few nano amps or pico amps). In this mode, both collector base junction and emitter base junction are reverse biased. In this mode, current flows between emitter and collector and the amount of current flow is proportional to the base current. In active mode, two junctions are differently biased that means emitter-base junction is forward biased whereas collector-base junction is reverse biased. In this mode, the transistor is generally used as a current amplifier. Operating Modes of Transistorsĭepending on the biasing conditions like forward or reverse, transistors have three major modes of operation namely cutoff, active and saturation regions. If you are looking for working of MOSFET as a Switch, then first learn the basics of MOSFET. These two transistors can be configured into different types like common emitter, common collector and common base configurations. In PNP transistor, N-type material is sandwiched between two P-type materials whereas in case of NPN transistor P-type material is sandwiched between two N-type materials. Both these function in the same way but they differ in terms of biasing and power supply polarity. This collector is large when compared to the other two regions so it can dissipate more heat.īJTs are of two types: NPN and PNP. The collector terminal is moderately doped and collects electrons from base. Base terminal is lightly doped and passes the emitter-injected electrons on to the collector. The emitter is a heavily doped terminal and emits electrons into the base. The transistor has three regions, namely base, emitter and collector. The name bipolar indicates that two types of charge carriers i.e., Electrons and Holes conduct current in the BJT, where holes are positive charge carriers and electrons are negative charge carriers. It is a current controlled device, where the output current is controlled by the input current. Whenever we say the term ‘transistor’, it often refers to BJT. It consists of two PN Junctions coupled back-to-back with a common middle layer. The Bipolar Junction Transistor or simply BJT is a three-layer, three terminal and two junction semiconductor device. There are two main families of Transistors: Bipolar Junction Transistors (BJT) and Field Effect Transistors (FETs). This article mainly concentrates on the switching action of the transistor and gives a brief explanation of transistor as a switch. You can find Transistors in both digital and analog domains as they are extensively used for different application usage like switching circuits, amplifier circuits, power supply circuits, digital logic circuits, voltage regulators, oscillator circuits and so on. As one of the significant electronic devices, transistor has found use in enormous range of applications such as embedded systems, digital circuits and control systems. Transistors is a three-layer, three-terminal semiconductor device, which is often used in signal amplification and switching operations.
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