5W Driver Amp

Here is a 5W output 1-55 MHz amplifier for stand-alone QRP operation or to drive the 100W MRF101 or 500W  AN1819 amplifiers to full power with lower drive level.

The amp can be built with only the output stage for a drive of 100-200 mW or add an MMIC to lower the drive to the 1-2 mW range.

The circuit uses a NXP AFT09MS015N with a 4:1 output transformer which can develop over 7W with 13.8V DC input. 

The gain is about 20 dB with the output stage alone and about 40 dB with the MMIC. The input has a place for a resistive attenuator so you can adjust the gain for your system.

If you don't need the pre-driver, put 0 ohm resistors in for C14 and C15 and don't populate U1, C2, C12, C13, C16 and L2. 

NXP recommends 100 mA bias so set VR1 for 10 mV across R5.

A heatsink is required for operation. The hole pattern is for an 1/8th brick DC-DC converter heatsink like a Wakefield 567-94AB.