Hi All,
Refer to LMH6881 datasheet , single-ended input impedance is about 50 Ω . Actually I use vecter network analyzer to measure the input impedance and found the single-ended input impedance is very low and about 4Ω. I checked PCBA signal path impedance and its impedance is about 50Ω , but after LMH6881 soldering , the impedance changed from 50Ω to 4Ω .
Could anyone advise it , thanks in advance.