I have a small doubt regarding the cascaded amplifier. In my design i want to have 55 dB gain, i am thinking to use 3 cascaded HMC618a because my RF signal input is less than -60dBm.
1. do i use 3 cascaded HMC618a or i can use 2 cacade HMC619a and 1 YSF 2151+ (which is MPA and from minicircuit) . ?
2. For power supply,can i use one HMC976 for all three LNA ?
Thanks & Regards
The HMC619 is obsolete and, even if you were able to obtain it, would thus be no longer recommended.
You should be able to cascade three of our HMC618A amps, but the total gain you obtain will have some frequency and supply voltage dependence so be sure to review the data sheet's gain vs. frequency plots. For your RF input signal < -60 dBm and assuming the highest Typical gain of +23 dB (from the data sheet's electrical Specifications Table), neglecting losses your cascade of three HMC618A amps could give you (23 dB + 23 dB + 23 dB) = +69 dB of gain (typical). In that case, the RF Pout from the three amp cascade could be as high as -60 dBm + 69 dB gain = +9 dBm, which remains below the OP1dB of the HMC618A.
I am not the applications engineer who supports the HMC976 but, at first glance it appears that a single unit might be adequate for biasing three of our HMC618A amps. The applications engineer for the HMC976 will have been automatically notified of your questions and will likely soon reply.
With respect to DC biasing multiple amps on the same PCB (whether in cascade or not), you may find useful the info contained within the following thread: