iii) Power Amplifier: Both current and voltage can be amplified. A transistor may serve various functions but basically it is used to amplify an electrical signal.

The power amplifier works on the basic principle of When collector current flows through such a high resistance, it produces a large voltage drop across it. This experimental (3) transistor class A audio power amplifier delivers 25mW into an 8Ω load, or 50mW into . The transistor has three terminals namely emitter, base and collector. Here a small change in the input voltage Vin is seen to change the emitter current IE appreciably as the resistance of the input circuit is low (due to the forward bias condition). Thus, a weak signal (0.1V) applied to the input circuit appears in the amplified form (10V) in the collector circuit. The transistor amplifier circuit is shown in the figure below. When a weak signal is applied to the input, a small change in signal voltage causes a change in emitter current (or we can say a change of 0.1V in signal voltage causes a change of 1mA in the emitter current) because the input circuit has very low resistance. This in turn changes the collector current almost in the same range due to the fact that the magnitude of the base current is quite less for the case under consideration. Your email address will not be published. Following on the same grounds, one can explain the amplifying action of other kind of transistor viz., Field Effect Transistor (FET). iv) Inverting Amplifier: Gives an amplified output out of phase from input. This large change in IC causes a large voltage drop across the load resistor RC which is nothing but the output voltage. Working with transistor will need you to test transistor. In figure 1, the transistor is biased for active region operation i.e. Figure 1 gives the basic circuit of a PNP transistor amplifier in common base (CB) configuration.

So a Application: Make your own computer speaker system. 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. This is basically a high gain amplifier with feedback that causes the LED to flash at a rate determined by the 10u and 330k resistor. 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. Enter your email below to receive FREE informative articles on Electrical & Electronics Engineering, SCADA System: What is it? CURRENT AMPLIFIER • The BJT(Bipolar Junction Transistor) behaves as an Current Amplifier. Be the first to review “Transistor as an amplifier science project”. For this, let us consider a npn bipolar junction transistor (BJT) biased to operate in active region (BE junction is forward biased while BC junction is reverse biased) as shown by Figure 1b. Save my name, email, and website in this browser for the next time I comment. Hence one gets the amplified version of the input voltage across the output terminals of the device which leads to the conclusion that the circuit acts like a voltage amplifier. This change is almost the same in collector current because of the transmitter action. transistor works as an amplifier. Transistors are fully-off in cut-off region while fully-on when operating in saturation region.

However its magnitude is less (usually in terms of μA as VBE is just around 0.6 V, in general). DC voltage applied to the junction, makes it remain in forwarding biased conditions. This constitutes nothing but the collector current IC moving into the collector. Difference Between Voltage Amplifier and Power Amplifier, Common Base Connection (CB Configuration), Two Wattmeter Method of Power Measurement, Difference Between Physical and Chemical Change, Difference Between Alpha, Beta and Gamma Particles, Difference Between Electrolytes and Nonelectrolytes, Difference Between Electromagnetic Wave and Matter Wave, Difference Between Kinetics and Kinematics, Difference Between Synchronous and Asynchronous Counter, Difference Between Analog and Digital Signals, Difference Between Stationary and Progressive Waves, Difference Between Positive and Negative Feedback. Electrical4U is dedicated to the teaching and sharing of all things related to electrical and electronics engineering. The forward bias applied between the base and the emitter terminals of the transistor causes the flow of base current, IB into the base region.


The well this can be done by this circuit . The DC voltage VEE keeps the emitter-base junction under the forward biased condition regardless of the polarity of the input signal and is known as a bias voltage. Now consider the npn transistor with the input signal applied between its base and emitter terminals, while the output being collected across the load resistor RC, connected across the collector and the base terminals, as shown by Figure 2. This is nothing but the current amplification, which leads to the conclusion that the npn transistor operating in its active region acts as a current amplifier. Such a device can operate in three different regions viz., cutoff, active and saturation.
The DC voltage applied to the junction, makes it remain in forwarding biased conditions. Save my name, email, and website in this browser for the next time I comment. However, we may use an NPN transistor and get the same results. Although the explanation provided is for the npn BJT, similar analogy holds good for even pnp BJTs. Further, these injected holes attract the electrons in the emitter region towards them, resulting in the recombination of holes and electrons. In order to build an amplifier, all you need are a transistor, a power source, some resistors, and some capacitors. Full disclaimer here. Required fields are marked *. JE is… Thus even after recombination effect, much more electrons will be left free. Explanation. So a small input voltage results in a large output voltage, which demonstrates that the transistor works as an amplifier. (Supervisory Control and Data Acquisition), Programmable Logic Controllers (PLCs): Basics, Types & Applications, Diode: Definition, Symbol, and Types of Diodes, Thermistor: Definition, Uses & How They Work, Half Wave Rectifier Circuit Diagram & Working Principle, Lenz’s Law of Electromagnetic Induction: Definition & Formula. Here, in general, the emitter will be heavily doped, the base will be lightly doped and the collector will be moderately doped. Such a device can operate in three different regions viz., cutoff, active and saturation. 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. The reason behind such a behavior can be understood by analyzing the working of transistor in terms of charge carriers. The end result is that if we bias the transistor so that its base-emitter PN junction is forward-biased (base about 0.7V more positive than the emitter for an transistor), then a small NPN current flow in the base terminal corresponds toa much larger current flow in the collector terminal: the BJT transistor is a current amplifier The transistor raises the strength of a weak signal and hence acts an amplifier. 24 thoughts on “ One-transistor audio amplifier for Arduino projects ” fatmi January 21, 2012 at 9:39 am Ifound my way to finish all the steps you wrote on the arduino. Further the base will be narrow, the emitter will be broader and the collector will be much broader. Now consider the npn transistor with the input signal applied between its base and emitter terminals, while the output being collected across the load resistor RC, connected across the collector and the base terminals, as shown by Figure 2. These electrons now cross the narrow base region and move towards the collector terminal influenced by the bias applied between the collector and the base regions. Amplifier 3. they can be used to increase the strength of the input signal without altering it significantly. The transistor amplifier circuit is shown in the figure below. Good explanation of transistor as an amplifier, Your email address will not be published. Mathematical expression for the voltage gain associated with this phenomenon is given by From this it can be noticed that by varying the current flowing into the base region (IB), one can obtain a very large variation in collector current, IC.