Thermal Performance

The AOM driver was designed to operate with a 24 V DC fan, which cools the high power amplifier. However, the fan produces a large amount of acoustic noise, which can cause problems in some laboratory environments. This page contains a few notes on operating the driver with and without the fan.

With the fan operating the GaN amplifier should remain within 10 degrees Celsius of ambient.

• Without the fan, at 20 degrees Celsius ambient and the input terminated, the amplifier heatsink stabilized at 50 degrees.
• At 0 dBm input power, the amplifier heatsink stabilized at 54 degrees.
• When I increased the power to 5 dBm, the amplifier heatsink stabilized at 59 degrees.
• At 10 dBm input, the amplifier heatsink stabilized at 64 degrees.

The absolute maximum rating for the HMC1099 amplifier is 85 degrees, so 10 dBm input is pushing the limit given that the chip will be at a higher temperature than the heatsink. Additionally, I did this testing with the tracking generator sweeping from 1 MHz to 1.2 GHz. Because the drain current is a function of frequency, the stable temperature may also change under constant frequency operation. Make sure to test the box yourself and ensure that your lab temperature is reasonably stable if you are considering operation with the fan disabled.

Additional notes:

• Operating with the box lid removed reduces the temperature by about 5 degrees.
• The quiescent current at the highest temperature is increased by 5 to 10 mA, which should not strongly adjust the amplifier's performance.
• All testing was done with the driver horizontal. Better performance might be possible if the driver box was turned on its side.