A Class B tuned amplifier is an electronic circuit that amplifies high-frequency signals with high efficiency and low distortion.
It is a type of push-pull amplifier that uses a tuned circuit to select a specific frequency. Class B tuned amplifiers are widely used in applications such as radio and television broadcasting, telecommunication, and radar systems.
Features of Class B tuned amplifier
- High efficiency due to the push-pull configuration
- Low distortion due to cancellation of even-order harmonics
- Utilizes a tuned circuit for frequency selection
- Consists of two transistors in a push-pull configuration
- Each transistor conducts for only half of the input signal cycle
- Output signal is taken from the center tap of the tuned circuit
Working of Class B tuned amplifier
The Class B tuned amplifier consists of a tuned circuit and two transistors arranged in a push-pull configuration. The tuned circuit is connected between the collector terminals of the transistors, and the input signal is applied to the base terminals of the transistors. The transistor conducts only for half of the input signal cycle.
During the positive half-cycle of the input signal, the transistor connected to the positive supply voltage conducts, while the transistor connected to the negative supply voltage remains in the cut-off region.
During the negative half-cycle of the input signal, the roles are reversed, and the transistor connected to the negative supply voltage conducts, while the transistor connected to the positive supply voltage remains in the cut-off region. The output signal is taken from the center tap of the tuned circuit.
Uses of Class B tuned amplifier
Class B tuned amplifiers are often used in applications where high efficiency and power output are essential. They are commonly found in radio-frequency (RF) power amplifiers and audio amplifiers. Class B amplifiers operate near the cutoff point, where each half of the input signal is amplified by a separate transistor. This design minimizes power dissipation when the input signal is small, leading to better efficiency compared to Class A amplifiers.
- Radio Transmitters: Class B tuned amplifiers are used in RF power amplifiers for radio transmitters to amplify the carrier signal before transmission. Their high efficiency makes them suitable for boosting RF signals without excessive power loss.
- Audio Amplifiers: While Class B amplifiers can introduce some distortion due to the crossover distortion at low signal levels, they are used in audio amplifiers when efficiency is important, such as in car audio systems and portable speakers.
- Inductive Heating: These amplifiers can also be used in induction heating systems, where they help in generating high-frequency magnetic fields to heat conductive materials like metal.
- RF Generators: Class B tuned amplifiers find application in RF signal generators, where they amplify the generated signal before it’s transmitted or used for testing purposes.
- RF Plasma Generators: In plasma systems for scientific research or industrial processes, Class B tuned amplifiers can be used to drive RF plasma generators, which produce high-energy plasma for various applications.
Applications of Class B tuned amplifier
- Radio and Television broadcasting
- Telecommunication
- Radar systems