Other Parts Discussed in Thread: LMH32404
Tool/software:
Could you please walk me through the design logic with the 1:1 balun on the output of this eval kit?
The LMH32404 has a differential output impedance of 21 ohms, and the eval kit places 24.9 Ohm series resistors on each of the legs of the differential outputs (for CH1, it's R1 and R4). This works out to a total differential output impedance of 70.8 Ohms. The signal then goes through a 1:1 balun for differential-to-single ended conversion. The eval kit datasheet claims that this is a 50-ohm output, yet based on the preceeding, this is actually a 70.8 Ohm output. Is there something I'm missing here? Why does the output appear not to be matched to 50 Ohms? I would have anticipated either R1/R4 or the balun impedance ratio to be selected to provide a true 50 Ohm matched output.
