Class B amplifier is a type of electronic amplifier that uses two active devices, such as transistors or vacuum tubes, to amplify an input signal. Class B amplifiers are known for their high efficiency, but can suffer from a phenomenon called crossover distortion, where the output signal contains distortion near the zero-crossing point of the input signal.
Class B amplifiers are commonly used in applications where high efficiency is important, such as in power amplifiers for loudspeakers, and in radio frequency amplifiers. However, they may not be suitable for high-fidelity audio applications where low distortion is a key requirement.
Features of Class B Amplifier
The main features of a Class B amplifier are:
- High efficiency: Class B amplifiers are more efficient than Class A amplifiers, as they only draw current when there is an input signal.
- Low quiescent current: Quiescent current is the current that flows through the amplifier when there is no input signal. Class B amplifiers have a low quiescent current, which reduces power consumption.
- Crossover distortion: Class B amplifiers can suffer from a type of distortion called crossover distortion, which occurs near the zero-crossing point of the input signal.
- Push-pull configuration: To reduce crossover distortion, Class B amplifiers are often used in a push-pull configuration, where two active devices work together to amplify the input signal.
- Suitable for high-power applications: Class B amplifiers are commonly used in high-power applications, such as power amplifiers for loudspeakers and radio frequency amplifiers.
Working of Class B Amplifier
A Class B amplifier works by using two transistors or tubes to amplify an input signal. One device handles the positive half of the signal, while the other handles the negative half. This results in a high-power output with high efficiency. However, to reduce distortion caused by a gap between the two devices at the zero-crossing point of the signal, a small amount of biasing current is necessary.
Applications
Class B amplifiers are used in a variety of applications where high power output and high efficiency are required. Some common applications are:
Power Amplifiers
Class B amplifiers are commonly used in power amplifiers for loudspeakers, as they can produce a high power output with high efficiency.
Radio Frequency Amplifiers
Class B amplifiers are used in radio frequency amplifiers to boost the power of a radio signal for transmission.
Switching Power Supplies
Class B amplifiers are used in switching power supplies, where they help to convert the input voltage into a regulated output voltage.
Battery-Powered Devices
Class B amplifiers are also used in battery-powered devices such as portable audio players and mobile phones, where they help to conserve battery life.
Automotive Amplifiers
Class B amplifiers are used in car audio systems to provide high power output while minimizing power consumption.
Industrial and Commercial Applications
Class B amplifiers are used in a variety of industrial and commercial applications, such as public address systems, paging systems, and intercom systems.