electrown.com Class B and Class C amplifiers differ primarily in their conduction angles and efficiency, with Class B amplifiers conducting for 180 degrees of the input signal and offering moderate efficiency and linearity, whereas Class C amplifiers conduct for less than 180 degrees, providing higher efficiency but more distortion, typically used in RF applications. Explore this article to understand which amplifier suits Your specific audio or radio frequency needs.
Table of Comparison
| Feature | Class B Amplifier | Class C Amplifier |
|---|---|---|
| Operation Angle | 180deg conduction angle | < 180deg, typically 90deg to 120deg conduction angle |
| Efficiency | Up to 78.5% | Up to 80-90% |
| Distortion | Moderate crossover distortion | High distortion, requires tuned circuits |
| Application | Audio amplification, push-pull configurations | Radio frequency (RF) amplification, transmitters |
| Output Waveform | Half sine waves combined for full output | Pulsed output, amplified via resonant tank |
| Biasing | Biased at cutoff point | Biased below cutoff |
| Signal Fidelity | Good for audio signals | Not suitable for audio, optimized for RF |
Introduction to Audio Amplifier Classes
Class B amplifiers operate by conducting current through each output device for half of the input signal cycle, providing higher efficiency around 70% but introducing crossover distortion due to signal switching. Class C amplifiers conduct for less than half the input cycle, making them unsuitable for audio amplification because they generate significant distortion yet are highly efficient and mostly used in RF transmission. Audio amplifier design balances fidelity and efficiency, with Class B favored for moderate efficiency and improved linearity over Class C, which is primarily reserved for non-audio applications due to its nonlinear operation.
Overview of Class B Amplifiers
Class B amplifiers operate by using two transistors that conduct during opposite halves of the input signal cycle, resulting in greater efficiency compared to Class A amplifiers. These amplifiers typically achieve efficiency levels up to 78.5%, making them suitable for applications where power conservation is important. Your audio system benefits from reduced heat generation, although Class B designs may introduce crossover distortion due to the brief moment transistors switch between on and off states.
Overview of Class C Amplifiers
Class C amplifiers operate with a conduction angle of less than 180 degrees, making them highly efficient but suitable mainly for radio frequency (RF) applications due to their significant signal distortion. Unlike Class B amplifiers, which conduct for exactly 180 degrees and offer a balance between efficiency and linearity, Class C amplifiers prioritize power efficiency over linearity, resulting in higher output power with lower signal fidelity. Your choice between these amplifiers depends on whether you need high efficiency for RF transmission (Class C) or better linear amplification for audio signals (Class B).
Key Operational Differences Between Class B and Class C
Class B amplifiers conduct current during exactly half of the input signal cycle, resulting in higher efficiency but potential crossover distortion, while Class C amplifiers conduct for less than half the cycle, producing higher efficiency and significant distortion requiring tuned circuits for signal correction. Class B is commonly used in audio amplification due to its lower distortion, whereas Class C is preferred in radio frequency transmission where high efficiency and narrowband operation are critical. The conduction angle in Class B is 180 degrees, contrasting with less than 180 degrees for Class C, directly impacting their applications and performance characteristics.
Efficiency Comparison: Class B vs Class C
Class B amplifiers typically achieve maximum efficiency up to 78.5% by conducting current for half of the input signal cycle, minimizing transistor power dissipation. In contrast, Class C amplifiers exhibit higher efficiency, often exceeding 80%, by conducting for less than 180 degrees of the input waveform and operating with significant distortion that is suitable mainly for RF applications. The efficiency advantage of Class C amplifiers makes them preferable in high-frequency transmitters, whereas Class B amplifiers balance efficiency with linearity for audio amplification.
Linearity and Distortion Analysis
Class B amplifiers exhibit moderate linearity but suffer from crossover distortion because each transistor conducts for only half of the input signal cycle, leading to a non-linear region around the zero-crossing point. Class C amplifiers operate with high efficiency but are highly nonlinear and produce significant distortion, making them suitable primarily for RF applications rather than audio amplification. Your choice depends on whether linearity and low distortion are critical, in which case Class B offers a better compromise, despite some distortion, compared to the inherently nonlinear Class C design.
Typical Applications of Class B Amplifiers
Class B amplifiers are extensively used in audio amplification systems, such as loudspeakers and PA systems, due to their higher efficiency compared to Class A amplifiers. They find applications in radio frequency (RF) transmission, where efficiency and linearity are balanced to ensure signal clarity and power conservation. Automotive audio systems and battery-powered portable devices also leverage Class B amplifier designs to maximize battery life while delivering adequate audio performance.
Typical Applications of Class C Amplifiers
Class C amplifiers are primarily used in high-frequency applications such as RF transmitters, where efficiency and power output are critical. They operate with a high level of distortion, making them unsuitable for audio signals but ideal for continuous wave (CW) or frequency modulated (FM) signals in communication systems. Your choice of a Class C amplifier is optimal for scenarios requiring high power efficiency and minimal linearity.
Advantages and Disadvantages of Each Class
Class B amplifiers offer high efficiency, typically around 70%, due to their push-pull operation that reduces power loss, but they suffer from crossover distortion at zero input signal, which affects audio fidelity. Class C amplifiers provide even higher efficiency, often exceeding 80%, by conducting for less than half of the input signal cycle, making them ideal for RF applications, yet they generate significant distortion, rendering them unsuitable for high-fidelity audio amplification. The trade-off between efficiency and linearity positions Class B amplifiers for audio purposes with some distortion mitigation, while Class C amplifiers excel in non-linear, high-frequency uses where signal purity is less critical.
Which Amplifier Class Suits Your Needs?
Class B amplifiers deliver high efficiency with minimal power loss, making them ideal for applications requiring energy conservation and moderate audio fidelity. Class C amplifiers provide even greater efficiency but at the expense of signal distortion, which restricts their use primarily to radio frequency transmission where a clean waveform is less critical. Choosing between Class B and Class C depends on priorities such as audio quality versus power efficiency and the specific use case, whether for high-fidelity audio amplification or RF signal generation.
class B vs class C amplifier Infographic
