AD8376 Filter Matching

Hi, actually I'm working in an interface between the ADL5380 and the AD8376 chip. The ADL5380 specfifies that using a high impedance load like for example 500 Ohm you'll get some  extra gain.

The AD8376 has internal termination of 150 Ohm differential.

The design decision comes now. I need to tune a filter between the ADL5380 and the AD8376.

From this point of view, the first alternative is

- To use a 150 Ohm diff like the load (directly using the input impedance like load) and to match it with a filter that adapt the 50 Ohm differencial in the source with this 150 Ohms differential in the load.

- A second option is to add a resistor of 37.5 Ohm in each terminal in order to get 25 Ohm SE in the load or 50 Ohm differential. In this case we'll have a filter between the 50 Ohm source and the 50 Ohm load.

Q1: The first alternative presents more gain in voltage. Does the second-one presents any advantage over the first-one?

Q2: There is any advantage using filters with the same load and source impedance?

Q3: Where is the limit of Impedance in the load? if the gain improves when it grows, why not use 1KOhm, 10K...?

Q4: When we make the conversion over the load resistance, if we increase the voltage, does the current decrease? It it's like this, does it have any implication?

Thanks in advance!

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