8/30/2023 0 Comments Fet transistor as a switchThe input impedance is very high in the range of 100M ohms. The input impedance is very low in the range of 1K ohms. The drain and source can be interchanged since the drain should be more positive. The emitter and base cannot be interchanged or swapped. The Gate voltage is reversed biased while the drain voltage is maintained higher than the source. The B-E junction is forward biased and the B-C junction is reversed biased. It is a voltage-controlled current device. It is a current-controlled current device. The 3 terminals of FET are Source Gate and Drain. The 3 terminals are named emitter, base and collector. The FET construction is comparatively difficult. The two types of FET are JFET and MOSFET, each with N-channel and p-channel as well.īJT construction is comparatively easier. The current flow is due to either electrons or holes, therefore, named unipolar transistor. The current flow is due to the flow of majority charge carriers.Ĭurrent flow is due to both electrons and holes, therefore name bipolar transistor. The current flow is due to the flow of majority as well as minority charge carriers. BJTīJT stands for Bipolar Junction Transistor. The following comparison table shows the main differences between BJT and FET transistors. Thyristor and Silicon Controlled Rectifier (SCR) – Thyristors Applications.Bipolar Junction Transistor (BJT) | Construction, Working, Types & Applications.Therefore, FET consumes very low power and is more energy efficient. Due to which there is no energy consumption during operation. the drain and the source terminal can be interchanged by maintaining the more positive voltage at the drain terminal.įET does not have any current flow at its base or it is very negligible. The drain terminal should be connected to a more positive voltage as compared to the source terminal. There is very little difference between the source and drain terminal. Therefore FET is also known as a voltage-controlled current device. Therefore, the voltage at the gate is used to control the output current. Increasing the reverse bias voltage at the gate increases the depletion region which results in increasing the current flow. The Gate is reversed biased in order to form a depletion region so that the channel between drain and source is formed. The Gate region is made from alternate material as compared to the channel. There are no PN junctions between the source and drain. The carriers enter the channel through the source and leave out at the drain. The channel refers to the path for the flow of current from source to drain terminal. Based on its construction, FET is available in two types i.e. The three terminals of FET are Drain, Gate and source. These transistors are also used for switching as well as amplification in electronic circuits. JFET (Junction FET) and MOSFET (Metal Oxide Semiconductor FET). There are two types of FET transistors i.e. Therefore, FET is also known as a unipolar transistor. The current flow in FET is due to the flow of only one type of charge carrier i.e. Difference Between NPN and PNP TransistorįET stands for the Field-Effect Transistor.This is why its temperature must be regulated using large heatsinks in order to work normally. Therefore, BJT gets hot very quickly and the temperature also affects its operation. Due to this, the BJT consumes more power which is wasted in the form of heat. Therefore, it consumes energy while operating. it is controlled by the current flow at its base terminal. BJT is not suitable for very high frequency.īJT works if there is any base current i.e. Therefore, the BJT has a low switching speed as compared to FET. the time it takes to switch off and switch on is large as compared to FET. Since the current flow is due to electrons as well as holes, the recovery time i.e. Therefore, the gain of the BJT amplifier is very high as compared to FET. Since the input (base) is forward biased, the input impedance of a BJT is very low in the range of 1K ohm while the output impedance is very high. while in the saturated and cutoff region, it acts as a switch to make or break a connection. In the active region, it acts as an amplifier where the collector current is proportional to the base current.
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