Search results
Results from the WOW.Com Content Network
Power amplifier circuits (output stages) are classified as A, B, AB and C for linear designs—and class D and E for switching designs. The classes are generally based on the proportion of each input cycle (conduction angle) during which an amplifying device passes current. [2]
This configuration is commonly used in the output stages of class-B and class-AB amplifiers. The base circuit is modified to operate the transistor in class-B or AB mode. In class-A mode, sometimes an active current source is used instead of R E (Fig. 4) to improve linearity and/or efficiency. [1]
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.
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 .
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 ...
An operational amplifier (often op amp or opamp) is a DC-coupled electronic voltage amplifier with a differential input, a (usually) single-ended output, [1] and an extremely high gain. Its name comes from its original use of performing mathematical operations in analog computers .
Linear amplifiers need to operate with class-A or class-AB biasing, which makes them relatively inefficient. While class C has far higher efficiency, a class-C amplifier is not linear, and is only suitable for the amplification of constant envelope signals. Such signals include FM, FSK, MFSK, and CW . [5] [6]
Audio amplifiers normally use a single valve in class A, or a pair in class B or class AB. An RF power amplifier is tuned to a single frequency as low as 18 kHz and as high as the UHF range of frequencies, for the purpose of radio transmission or industrial heating. They use a narrow tuned circuit to provide the valve with a suitably high load ...