# Operating a solid state power amplifier without a load?

I was wondering, assume you have a 144MHz FET based power amplifier and you drive it at full input power without a load connected what actually happens to the device? Do you have reflection of the expected output power?

My understanding is that reflections only occur when the length of a wire/trace is longer than lamda/10 (point at which you can model the wire as a transmission line), so I assume reflection of the output power will only take place if you connect a wire of this approximate length to the output?

• In normal conditions use, a PA is "quasi" at the limit of power. "Line or no line", If you don't use a load for the RF power amplifier (which is unprotected by a "reflexive" system), it is quite clear that it should be overloaded at 2 times its nominal power. The problem is only the fact it can "support" the overload. Note also that the destructive effect can be very fast (some ms). Jul 21 at 9:20
• But you should also read this ... advancedenergy.com/globalassets/resources-root/white-papers/… Jul 21 at 9:35
• @Antonio51 I guess I'm struggling to understand why there would be reflection if there is effectively no transmission line due to the length of the line being less than lamda/10. For example does a 1kHz 1W signal reflect the same amount of power due to an impedance mismatch than a 1W 1GHz signal? Jul 21 at 10:10
• @Antonio51 Thanks for the reference though! I appreciate it Jul 21 at 10:50