The transistor can be used as a switch if biased in the saturation and cut-off regions. The parameters of a good transistor mainly include different parameters namely high gain, high slew rate, high bandwidth, high linearity, high efficiency, high i/p impedance, and high stability etc. A transistor acts as an Amplifier, where the signal strength has to be increased. Amplification can be accomplished using vacuum tubes or semiconductor devices such as transistors or integrated circuits. This does not upset the emitter bias, because a low-reactance path around R, If a fixed collector current is assumed at some operating point, the collector voltage, V, In a phase relationship that opposes the input, a signal from the output of a device fed back to the input is called, Field-Effect Transistor (FET) Types | JFET & MOSFET Construction, Common Emitter Amplifier: Working & Circuit Diagram. Amplifiers are used in wireless communication. "name": "Transistor as an Amplifier: Working & Circuit | NPN Transistor Amplifier" "@type": "BreadcrumbList", In this article we will study how a transistor can function as an amplifier. Transistor is a semiconductor device with three terminals viz., Emitter (E), Base (B) and Collector (C) and thus has two junctions viz., Base-Emitter (BE) junction and Base-Collector (BC) junction as shown by Figure 1a. Because in CB configuration, the gain is <1, and in CC configuration, the gain is almost equivalent to 1. The main function of a transistor as an amplifier is to enhance the input signal without changing much. CURRENT AMPLIFIER • The BJT(Bipolar Junction Transistor) behaves as an Current Amplifier. From the above information, finally, we can conclude that a transistor can perform like an amplifier only when it is biased properly. Therefore, the applied weak signal at the input circuit will come out in the amplified form at the collector circuit in the output. Today in this article we are going to explain working of transistor as an amplifier. "@context": "http://schema.org", In most of the electronic circuits, we use commonly NPN transistor configuration which is known as NPN transistor amplifier circuit. The audio input is coupled to the base of Q1 through resistor R1 and capacitor C1. A disadvantage of this circuit, however, is the need for two power supplies or batteries. A transistor either works as a switch or as an Amplifier. [ The transistor will operate as an amplifier or other linear circuit if the transistor is biased into the linear region. The process of amplification has been an important step in many applications like wireless transmitted signals, wireless received signals, Mp3 players, mobile phones, and etc., The transistor can amplify power, voltage and current at different configurations. The transistor amplifier circuit is shown in the figure below. Because a transistors collector current is proportionally limited by its base current, it can be us… In the above circuit, the entire resistance will be equal to the amount of two resistors like R1 & R2. "@type": "ListItem", This circuit uses a single power source. In this case, the forward bias voltage VEE will set a constant emitter current, IE. }. Figure 4 shows a complete NPN transistor circuit. Transistors amplifiers are commonly used in applications like RF (radio frequency), audio, OFC (optic fibre communication) etc. It also opposes any increase caused by the input signal. The emitter and base of the transistor are connected in forward biased and the collector base region is in reverse bias. "itemListElement": Generally, the input circuit includes low resistance as a result; a little change will occur in signal voltage at the input which leads to a significant change within the emitter current. This allows current to flow (or not) in other parts of a circuit. A transistor is used as the active element. This bias is used for switching circuits. The similar supply voltage also decides the utmost collector current, as the transistor is activated that is in saturation mode. Forward and reverse bias in a PNP transistor amplifier circuit. Notice that the resistor RB has been omitted. The Vb (base voltage) can be measured with the potential divider network. By using the above formulas, voltage gain can be calculated for the amplifier circuit. Resistor R3 provides collector to base bias for Q1 and C3 is an AC by pass capacitor for the collector resistor R4. The collector, C, is connected through R, The most negative point in the circuit is the ground, and it is connected directly to the negative terminal of V, The voltage at the base, B, is less positive than the positive terminal of V, A switch is inserted in the base to control current through the emitter-collector. 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