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When Class-B amplifiers amplify the signal with two active devices, each operates over one half of the cycle. Efficiency is much improved over class-A amplifiers. [14] Class-B amplifiers are also favoured in battery-operated devices, such as transistor radios. Class B has a maximum theoretical efficiency of π/4 (≈ 78.5%). [15]
A radio-frequency power amplifier (RF power amplifier) is a type of electronic amplifier that converts a low-power radio-frequency (RF) signal into a higher-power signal. [1] Typically, RF power amplifiers are used in the final stage of a radio transmitter , their output driving the antenna .
6N3C power tube. A valve amplifier or tube amplifier is a type of electronic amplifier that uses vacuum tubes to increase the amplitude or power of a signal.Low to medium power valve amplifiers for frequencies below the microwaves were largely replaced by solid state amplifiers in the 1960s and 1970s.
Some audiophile equipment, such as amplifiers, continues to be point-to-point wired using terminal pins, [1] often in very small quantities. In this application modern point-to-point wiring is often used as a marketing design feature rather than a result of the economics of very-small-scale production.
This means that class AB and B amplifiers produce their lowest distortion percentage at near maximum amplitude, with poorer distortion performance at low levels. As the circuit changes from pure class A, through AB1 and AB2, to B, open-loop crossover distortion worsens. Class AB and B amplifiers use NFB to reduce open-loop distortion.
In practical design, the result of a tradeoff is the class AB design. Modern Class AB amplifiers commonly have peak efficiencies between 30 and 55% in audio systems and 50-70% in radio frequency systems with a theoretical maximum of 78.5%. Commercially available Class D switching amplifiers have reported efficiencies as high as 90%. Amplifiers ...
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The Williamson amplifier was published in 1947 as an article in Wireless World, and was a milestone which defined the mainstream topology for the majority of amplifiers thereafter. The design gave particular attention to a very high specification for the output transformer, in addition to being generally a consistently well worked-through design.