Hi

I am currently stuck on the following problem: I am using AD8132 as a line driver in a single-ended configuration. The signal that comes to the

input has 10MHz bandwidth. My struggle is: Do I have to make impedance mathing on the pcb traces on the first place? And the question is the

same for the outputs too.

I will appreciate any advice or help.

Thank, you.

Hi mocuZ,

I hope I'm understanding you correctly. I checked this out with our layout engineers to confirm. I don't think it's necessary to use a transformer on your input signal path. If you check Diff-amp calc, resistors RTP and RTN in the circuit will provide the necessary termination so that the line will ultimately see an impedance of 75 ohms. The calculation of RTP and RTN should be the same as the calculations in the application note that I gave you. So looking at the input of your circuit, with a 75-ohm source resistance, if you control your line impedance to 75-ohms and follow the calculated RTP and RTN, then you should have no problems with signal degradation due to reflections.

As for the output, using 49.9-ohms at the outputs is a good idea. If it goes to a twisted pair with an impedance of 100-ohms, just make sure you have a differential controlled line impedance of 100-ohms so that your circuit will work optimally. I apologize, I can't verify anything regarding the 22-mil width, although from what I got from the layout engineer, that width isn't unheard of. I found a thread on EZ which includes a tool for trace impedances. You could try it out and see if you can confirm anything: http://ez.analog.com/message/34551

I hope this helps!

Kris