AD8363: Using INHI vs. INLO for Wideband Applications

Document created by enash Employee on Oct 24, 2014Last modified by enash Employee on Aug 10, 2016
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Q. The AD8363 datasheet recommend driving the RF input through INHI for frequencies at or below 2.7 GHz and through INLO for operation above 2.7 GHz. If I have an application where I want one circuit to span a broad frequency range that includes 2.7 GHz and 3.5 GHz, which input should I choose.


A. You can use either depending on whether  your frequency range is concentrated above or below 2.7 GHz (that is the frequency at which we recommend switching from INLO to INHI.


As go go up in frequency driving INHI, you find that the transfer function loses some linearity above input power levels of around -10 dBm.  Switching over to driving the signal through INLO improves this a bit. However, if you do drive through INHI at frequencies above 2.7, you will still get performance that is fairly linear. And if you calibrate the transfer function at three points, as suggested in the Rev. A datasheet, that will improve things even further. The same argument applies to using INLO; it will still give good performance below 2.7 GHz, particularly if you 3-point calibrate the circuit.