Power Amplifier

Power Amplifier (PA) is an electronic device or circuit that boosts the power of a signal. Its main job is to take a weak input signal and amplify it to a level that is strong enough to drive a load—usually a loudspeaker, antenna, or other high-power device.

Basic Definition

A Power Amplifier increases the amplitude of a signal without significantly distorting its waveform. It’s typically the last stage in an audio, radio frequency (RF), or wireless communication system.

Key Characteristics

• High Output Power: Delivers significant electrical power to the load.

• Efficiency: Converts input power into output power with minimal loss.

• Linearity: Maintains signal integrity (especially important in communication systems).

• Gain: Ratio of output to input power.

Types of Power Amplifiers

Based on Operation

1. Class A – High linearity, low efficiency.

2. Class B – Better efficiency, some distortion.

3. Class AB – A compromise between A and B.

4. Class C – Very high efficiency, used in RF applications, low linearity.

5. Class D – Uses digital (switching) methods; very efficient; used in audio.

Based on Frequency

• Audio Power Amplifiers – Used in sound systems.

• RF Power Amplifiers – Used in transmitters and wireless communications.

• Microwave Power Amplifiers – For satellite, radar, etc.

Applications

• Audio Systems (home theaters, concert sound systems)

• Broadcasting (TV/radio transmitters)

• Mobile Communications (cell towers, smartphones)

• Military and Radar Systems

• Industrial Equipment (RF heating, lasers)

Important Parameters

• Output Power (Watts)

• Gain (dB)

• Efficiency (%)

• Input/Output Impedance

• Linearity/Distortion

• Thermal Management