This is the output amplifier (OPA2677) used in SDR, and all my transmitters are constructed with it. For power supply voltage up to 500mW, a single +10V power supply (dual ±5V power supplies) is OK, but for any power greater than that, a single +12V power supply is preferable, and the output terminal is OK as long as a 50Ω load is connected, but there is a risk of parasitic oscillation if the power is turned on with no load, so it is better to shunt it at around 1KΩ. I recently created this as a drive for experimenting with semiconductor linear amplifiers, and have collected some data, so I would like to introduce it. 　　　 It has some frequency response correction and is powered by a single +12V power supply. 　 　　 Increasing the value of R2/R9 increases the power gain, but the high frequencies drop. I actually use HF from 3.5M to 14M, and my equipment supports up to 28MHz, but 21M/28M has become a dead band recently because there is only noise whenever I listen to it. 　　　　Actual data

 

I tried to get distortion characteristics. I tried to get them at 100mW and 500mW for each band. 21MHz and 28MHz are for reference, but I think the characteristics are quite usable. There is not much difference between 100mW and 500mW. These are the results of actual measurement data.