4th semester project physics b.Sc mathematics
- 1. B.SC 4TH SEMESTER NAME:- RAMAN SINGH ROLL NO.:- 10623870443 Physics Power Point Presentation “Amplifiers And Their Classifications”
- 2. AMPLIFIER An amplifier is an electronic device that increase the power, voltage or current of a signal. Amplifiers are used in wireless communication and broadcasting and in audio equipment of all kinds.
- 3. CLASSES OF AMPLIFIER: There are four common classes of amplifier in the high-fidelity reproduction of audio: Class A Class B Class AB Class D
- 4. “CLASS A” Here are the characteristics of the class: The output device (transistor) conducts electricity for the entire cycle of input signal. In other words, they reproduce the entire waveform in its entirely. These amps run hot, as the transistors in the power amp are on and running at full power all the time. There is no condition where the transistor(s) is/are turned off; That doesn’t mean that the amplifier is never or can never be turned off; it means the transistors doing the work inside the amplifier have a constant flow of electricity through the. This constant signal is called “bias”. Class A is the most inefficient of all power amplifier designs, averaging only around 20. They usually waste at least 4-5 watts as heat.
- 5. They are the most accurate of all amps available, but at significant cost to manufacture, because of tight tolerance, and the additional components for cooling and heat regulation.
- 6. “CLASS B” In this amp, the positive and negative halves of the signal are dealt with by different parts of circuit. The output devices continually switch on and off. Class B operation have the following characteristics: The input signal has to be a lot larger in order to drive the transistor appropriately. This is almost the opposite of Class A. There has to be at least two output devices with this type of amp. This output stage employs two output devices so that each side amplifies each half to the waveform. Either both output devices are never allowed to be on at the same time, or the bias for each device is set so that current flow in one output device is zero when not presented with an input signal.
- 7. Each output device is on for exactly one half of a complete signal cycle. These amps run cooler than Class A amps, but the sound quality is not as pure, as there is a lot of “crossover” distortion, as one output device turns off and the other turns on over each signal cycle.
- 8. “CLASS AB” This is the compromise of the bunch. Class AB operation has some of the best advantages of both Class A and Class B built- in. Its main benefits are sound quality comparable to that of Class A and efficiency similar to that of Class B. Most modern amp designs employ this topology.Its main characteristics are: In fact, many Class AB amps operate in Class A at lower output levels, again giving the best of both worlds. The output bias is set so that current flows in a specific output device for more than half the signal cycle but less than the entire cycle. There is enough current flowing through each device to keep it operating so they respond instantly to input voltage demands.
- 9. There are quite a few excellent Class AB amps available. This is the design recommended for most general-use applications in home and car. Usually, parts choice rivals that of Class A amps, and dollar for dollar these are some of the best value in stereo amplification. There can be some variation in design principle, but generally these are well- designed amps since their function is very well-understood by audio designers.
- 10. “CLASS D” These amplifiers are erroneously called “digital” amplifiers by the press and many audio “experts.” Here’s the skinny on Class D: While some Class D amps do run in true digital mode, using coherent binary data, most do not. They are better termed “switching” amplifiers, because here the output devices are rapidly switched on and off at least twice for each cycle. Depending on their switching frequency, they may be “switched on” or “off” millions of times a second. Class D operation is theoretically 100% efficient, but in practice, they are closed to 80-90%. This efficiency gain is at the cost of high-fidelity.
- 11. Think of Class D amps as being similar to a switchable power supply, but with audio signals controlling, or modulating, the switching action. To do this, you use a technology called Pulse Width Modulation. Class D amplifiers are generally used for non-high-fidelity, or subwoofer applications.
- 12. CONCLUSION The quest for high-fidelity, coupled with efficiency has driven amplifier design for decades. Electrical properties of the available electronics and the never-bending laws of electrical behavior have created a multitude of solutions for those trying to design high-powered, great-sounding, and efficient amps. Look for the best balance of performance for the buck and let your ears be your guide and you’ll choose the best products, regardless of price and class.
- 13. THANK YOU