A power amplifier is a multi-channel electronic amplifier which amplifies low-voltage audio signals like the sound from electric guitar pick or radio scanner to a high sufficient level for powering speakers or headphones. The output from the amplifier's inverter is then fed to a speaker or headphone set. Power amplification is the technology used in multimedia systems. Multimedia systems combine various devices, like digital audio players and game consoles, tape, CD, DVD players and recorders and digital audio workstations with each other.
In order for an amplifier to be categorized as a true Power Amplifier, it must exhibit characteristics of efficiency and output power efficiency. The efficiency of an amplifier refers to the ratio between input power and output power. This is measured in watts per hour. The output power efficiency of a device is usually expressed as a ratio of maximum power drawn by the device (Voltage) to its maximum wattage, divided by its total maximum power consumption during its operation. While a true Power Amplifier can produce audible output, it is usually found in desktop and mobile music devices, in home stereos, as well as in some portable media players.
The distortion in a Power Amplifier occurs due to several factors, including short-circuits within the device, Impedance distortion caused by a connecting wire, or any combination of both short-circuits and Impedance distortion. Short-circuits, often caused by improper wiring, can occur even when the Power Amplifier is operating at full capacity. Impedance distortion is the result of a high output voltage being coupled into a lower input voltage
When designig a Power Amplifier, it is necessary to ensure that the output and input devices are designed in different classes. The two main classes are Class A and Class B. In a Class B amplifier, one side of the input signal wavesform is amplified while the other is un Amplified. To achieve this, the power amplifier uses a buffer to control the gain and threshold levels for the amplifier's output.
On the other hand, in Class A, the amplifiers work on a single device. For instance, single transistor (or SiT) Power Amplifiers can offer much less distortion than do Class B amplifiers. Class A also allows the power amplifier to be much smaller in size. Most of the time, the Power Amplifiers found in personal computers are in Class A; there are also hybrid units available which are in both classes.
On the other hand, Class AB power amplifiers are the most popularly used in present day high end stereo and home theater applications. These types of amplifiers utilize a switching device which limits the frequency response of the unit. This allows the amplifier to better control the distortion produced by the power amplifier input signal. Usually used in high power audio amplifiers where there are several output devices and not just one.
Class C: The C type of amp is designed especially to drive low power consumption speakers. However, they are not very efficient in driving high power speaker systems. Due to this, the distortion produced by the amplifier is much lower compared to other ampages. They are usually used in portable audio applications and they are very popular among hobbyist musicians.
These are the three major classifications of power amplifier which differ in the way they handle large or small input signals. The choice of the type of amp to use really depends on your application. So, it would be a good idea to first study the needs of the audio application you are going to use the amplifier for.
Class D: The D shaped power amplifier is characterized by its two-chip input signal process which is composed of a high-sides and a low-side. It operates on a single channel only. The reason behind this design is that it can efficiently handle large numbers of input signals without any problem. However, this amp tends to burn out more frequently than any of the other ampages due to its two-chip processing. Due to this, some manufacturers have designed the amp with a multi-chip circuit that reduces the risk of damage from overheating and fluctuating currents.
Class A: The Class A power amplifiers are very famous for their ability to boost the input signal to a desired level. However, its output stage is characterized by its ability to control the voltage. To achieve this, the amp controls the amount of power going into the amplifier and also adjusts the amount of voltage before it goes to the actual speaker. One of its advantages is that there is no need for any noise buffering as the signal has already reached the required level. Due to its ability to deliver power continuously, the amplifier has been often used in desktop units.
Class B: The Class B output power amplifier is often used as the main power amplifier for small devices. Compared to the Class A, the B output power amplifier delivers limited power amplification. In addition, it allows the device to be set for balanced or uncapped output power. This allows the user to control the volume level of the small devices without affecting the performance of the large devices.