An amplifier is an electronic device increases the amplitude of a small signal to a useful level, even maintaining small signal’s detail. This is known as Linearity.
FIGURES OF MERIT
1) Gain: Ratio between the magnitude of output and input signals.
2) Bandwidth: The Width of the useful frequency range.
3) Efficiency: The ratio between the power of the output and total power consumption.
4) Linearity: The degree of proportionality between input and output.
5) Noise: A measure of undesired noise mixed into the output.
6) Output Dynamic Range: The ratio of the largest and the smallest useful output levels.
7) Slew Rate: The maximum rate of change of the output.
8) Rise Time: Characterize the step response.
9) Stability: The ability to avoid self-oscillation.
AMPLIFIER GAIN
The measure of how much an amplifier “amplifies” the input signal, found by observing the difference between the input and output signals is known as the Gain of amplifier.
Amplifier gain can be calculated by the ratio of output divided-by the input.
AMPLIFIER CLASSES
Audio power amplifiers are classified in an alphabetical order according to their circuit configurations and the mode of operation. These different amplifier classes range from a non-linear output with low efficacy to a non-linear output with high efficacy.
CLASS A AMPLIFIER
The general property of class A amplifier is that the output transistor always has the significant current flow hence have a large quiescent current. Quiescent current is defined as the current level in the amplifier even if there is no input signal. Class A amplifiers are made more efficient by employing Double-ended arrangement, employs two complimentary transistors.
Some form of heat sink is required to maintain the heat develops in the output transistor of class A amplifier. Hence class A amplifier are inefficient as most of the DC power is converted to heat.
Class A Power Amplifier
Class A Bias
CLASS B AMPLIFIER
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