What Is a Radio Frequency Amplifier?

Benjamin Arie

A radio frequency amplifier is an electronic device that converts a weak signal into a radio signal with more power. Radio frequency (RF) amplifiers are often used to boost a radio message before it is transmitted by an antenna. Alternately, an RF amplifier can be used to increase the power of weak reception. Most amplifiers can be tuned to a desired frequency range, which allows the device to boost specific signals very efficiently.

Radio frequency amplifiers can be used to boost the signal of a shortwave field radio.
Radio frequency amplifiers can be used to boost the signal of a shortwave field radio.

Transistors form the core of a radio frequency amplifier, and allow it to increase signal power. A transistor is a solid-state component that functions as a switch or relay for electricity. When a transistor is activated by a low-power signal, it closes two connections. These two links can handle much higher power than the low-power signal input. A transistor works in a similar fashion as a person activating a light switch, except it can be toggled very rapidly and requires only an electrical signal to complete the connection.

The transistors within a radio amplifier can be switched on and off at the same frequency as a radio signal. This results in the original signal being replicated at a much higher power level. To use the light switch example, this functionality is the equivalent of a person receiving a faint Morse code signal and toggling a high-power lamp in the same pattern. The transistors of a radio frequency amplifier are able to perform this switching feature many times faster than a human, and many amplifiers can switch a signal thousands or even millions of times per second.

A radio amplifier must be designed properly to handle the desired amount of output signal. If the transistors within an amplifier are not large enough, they can quickly overheat and melt. Many amplifiers use special pieces of metal, called heat sinks, to dissipate excess heat and prevent the transistors from becoming damaged. Very large RF amplifiers employ several stages of connected transistors; each set is designed to progressively handle more power.

RF amplifiers have many practical applications. One of the most common uses is to boost the data or voice signal that is sent or received via an antenna. Radio amplifiers can also increase the strength of radio pulses, such as those used in a radar unit. Common household appliances also use these types of amplifiers. Microwave ovens rely on an amplifier to create high-power radio waves, which excite the molecules within food and cause heat to increase.

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