Differences between Rf power amplifier types

Jun 16, 2020

At first glance, there are many types of RF amplifiers, and it may be overwhelming to narrow the specifications of which RF power amplifier is most suitable. Most RF power amplifier types come from common transceivers, receivers, transmitters, radar and modulation circuits, and system level type specifications.

Broadband Amplifier
Broadband amplifiers are designed to provide moderate gain over a wide bandwidth, while maintaining a low noise figure. These types of amplifiers are usually used in receiver circuits at the front end of the antenna without the need for low-noise amplifiers, and in receivers that require additional gain and need to consider noise.

Logarithmic Amplifier
A logarithmic amplifier is an amplifier with a gain curve in which the output voltage is a multiple of the natural logarithm of the input voltage. This type of amplifier is specifically used in applications that require this behavior. This can be achieved by using variable gain circuits, variable attenuators and fixed gain amplifiers, depending on the application. These amplifiers, also known as linear-to-log converters, are commonly used as part of closed-loop control circuits to keep the signal power level of the main signal path constant.

Low Noise Amplifier
Low noise amplifiers make full use of any part of the transmitter or receiver design. These parts need to amplify the low power signal to the working power level without introducing significant noise or phase noise. This may be at the output of the oscillator, enhancing the signal to drive the mixer, or at the input of the antenna to sufficiently increase the power of the signal for ease of processing by the demodulation and digitization circuit.

Coaxial and Waveguide Power Amplifiers
The power amplifier is the main power amplifier in the radio frequency front end of the transmitter, which converts the low-power signal from the communication and radar equipment into a high-power transmission sent to the antenna. The goal of the power amplifier is to increase the gain of the signal to a high power level without degrading the signal quality.

Linear Amplifier
A linear amplifier is usually an RF power amplifier, specifically designed to provide highly linear performance, with a proportional linear relationship between input and output. Therefore, linear amplifiers are designed to optimize linearity above other design considerations, especially under wide load conditions. Linear amplifiers are most commonly used in transmitters and test equipment that require high linear power.

Bidirectional Amplifier
The bidirectional amplifier is a combination of a transmitter and a receiver, and is intended to serve as an intermediate node for receiving a weak signal and amplify the signal for the purpose of retransmission and acquisition at an electrically long-distance location. Bidirectional amplifiers are often used to extend communication networks to remote locations without the need to install other infrastructure. It can be used to cover a larger land area, or used with coaxial transmission lines to extend signals or communication systems to longer distances underground or within facilities.

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