The RF power amplifier stage is usually the final active block of any electronic system that is transmitting RF power. Relatively low power RF signals are amplified to produce a more powerful signal in order to be transmitted over greater distance. RF output power can range from a few mW to MW, depend by application. RF amplifiers before were all made using vacuum tubes but modern RF amplifier nowadays uses solid state devices like MOSFET, TMOS-FET, Bipolar junction transistors, and IGBT to amplify RF signals.
This circuit features the Freescale AFT05MP075GNR1 RF power LDMOS transistor as its RF amplifier solid state device. With the use of some components and proper board layouting, Freescale was able to create a 70 watts RF power amplifier with a gain of 18.5dB. This circuit requires a 12.5Vdc power supply able to provide the maximum power this LDMOS transistor can give. In this circuit, AFT05MP075GNR1 was configured to amplify RF signal with a carrier frequency of 520MHz suitable for UHF band mobile radio applications.
The Freescale AFT05MP075GNR1 was designed for mobile two-way radio applications with frequencies ranging from 136 to 520 MHz. It can be configured as a narrowband or wideband RF power amplifier. The high gain, ruggedness and broadband performance of this device make it ideal for large-signal, common source amplifier applications in mobile radio equipment. It can operate exceptionally in a very wide temperature range, from -40 to +150 degree Celsius. Though this device handles wideband application, it can still give full power across the band.
For more detail: Narrowband RF Power Amplifier (520MHz)