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Application Note: A Broadband, 500-Watt, Push-Pull Amplifier
By Ben Caccavale, Spectrum Devices
This application note describes a reference design for a power
amplifier that provides continuous operation in the 2 to 30 MHz
HF band, achieving 500 watts with a minimum gain of 14 dB.
The module uses a push-pull design, which reduces even order
harmonics. Operating at 50 volts, this reference design uses
broadband 9:1 impedance transformers and negative feedback to
maintain a gain flatness of 1 dB across the frequency band. A
built-in bias power supply allows for Class AB operation. A 1,700-
watt power amplifier system can be realized by combining four
power modules with a broadband four-way splitter and combiner.
The push-pull power module uses Spectrum Devices' HF50-
220 bipolar power transistors and can be modified to use the
thermally enhanced HF50-250 power transistors.
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