What is the limitation when using the part HMC241ALP3 below 100MHz? The former part HMC241LP3 is defined DC to 4GHz, and for the best of my understanding both parts HMC241ALP3 and HMC241LP3 are FFF. Please advise what is the performance in the frequency range 20 to 100MHz
That is correct - the HMC241LP3 and the HMC241ALP3 are FFF compatible. Unfortunately, on the older HMC parts, the lower frequency was incorrectly defined in the datasheet. They could not be operated at true DC frequencies. The lower frequency cutoff for the osbolete, HMC241LP3, was ~300MHz.
However, the part can be used 20-100 MHz. There will be degradations in power handling and linearity. The maximum power the part can handle, the P1dB, and IIP3 may be lower.
Hope this helps.HK.