AnsweredAssumed Answered

AD8376 Filter Matching

Question asked by Zartagal on Mar 28, 2014
Latest reply on Mar 31, 2014 by Qui

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!

Outcomes