Francois, all

I believe that all WiFi systems employ OFDM modulation schemes.

This is a multi carrier  modulation with an inherent requirement for linearity in any amplifiers.

 

Because of the multi-carrier nature of the signal,  any amplifier must be able to handle, to some extent, the elevated peak voltages associated with this.  The crest factor of an OFDM signal is regarded as 10dB.  For practical amplifiers you don’t need to necessarily rate them at 10 times the wanted power out.  Depending on the  tolerance to  intermodulation product errors, you may get away with rating the amplifier  with 6dB headroom (more or less)  I suspect these amps have less headroom, but because the  peak voltages are statistically distributed, the error rate probably doesn't increase too much, and given the robust nature of Wifi, you get away with it ( or the user  doesn't notice that the error rate has gone up)

 

 

This is probably how is reported that you can get 4W out of these amplifiers, which i presume was measured  somewhere about the 1dB Compression point, ie satisfactory for  SSB

 

At the rated 2.5W, it will almost certainly be really quite linear and below the 1dB compression point.

 

They do indeed look like good value.

I am tempted to get one to play with myself.

Regards

Mark GM4ISM