RF Amplifier Circuits

  

A linear amplifier is an electronic circuit whose output is proportional to its input, but capable of delivering more power into a load. The term usually refers to a type of radio-frequency (RF) power amplifier, some of which have output power measured in kilowatts, and are used in amateur radio. Other types of linear amplifier are used in audio and laboratory equipment. An RF linear amplifier can be based on either solid state or vacuum tube technology.

Most commercially manufactured one to two kilowatt linear amplifiers used in amateur radio still use vacuum tubes (valves) and can provide between 10 to 20 times RF power amplification. For example, a transmitter driving the input with 100 watts will be amplified to 2000 watts (2 kW) output to the antenna. Solid state linear amplifiers are more commonly in the 500 watt range and can be driven by as little as 25 watts. However, AM radio broadcast transmitters of up to 50 kW are now solid state.
 
Large vacuum valves are still used for international long, medium, and shortwave broadcast transmitters between 500 kW up to 2 MW. The basic applications of the RF power amplifier include driving to another high power source, driving a transmitting antenna, microwave heating, and exciting resonant cavity structures. Among these applications, driving transmitter antennas is most well known. The transmitter–receivers are used not only for voice and data communication but also for weather sensing (in the form of a RADAR).
 
Microwave or RF heating is an industrial application which is also benefiting our homes in the form of microwave ovens. Class-A operation is characterized by a constant DC collector (or drain) voltage and current. This class of operation is required for linear amplifiers with severe linearity requirements including: Drivers in SSB transmitters where a 2-tone 3rd-order intermodulation of at least -40 dB is required. Drivers in TV transmitters where the contribution to the gain compression must be very low, i.e. not more than a few tenths of a dB.
 
 

Circuits


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The input/output transformer is wound on a Type FT37-75 ferrite core from Micrometals. A linear RF amplifier can be made in two ways: (l) with the aid of a linear active element, or (2) with a non-...

The 60 Watt linear amplifier is simple all solid state circuit using power mosfet IRF840. The IRF series of power transistors are available in various volt...

Radio frequency (RF) power amplifiers are the fundamental building blocks used in a vast variety of wireless communication circuits, radio and TV broadcasting transmitters, radars, wireless energy ...

circuit schematics in circuit test simple circuit diagrams electronic circuit schematics rf test equipment rf circuit simple circuit projects rf voltmeter circuits diagram rf millivoltmeter voltmet...

Special RF protection filters make it particularly suitable for powering FM transmitters, CB radios and linear amplifiers. Tried and tested design that uses a ... to the circuit connected to the su...

The ARRL site should be a good source for RF amps. They are a bit of a challenge for a first-time project, though. You might also Google for "linear amplifiers" to see if you can turn up something ...


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