Other Parts Discussed in Thread: LMH3401, ADC12DJ3200
Hello,
I am using the LMH3401 as a DC-coupled, single-ended to differential amplifier to drive an ADC12DJ3200. My single-ended signal is a positive, unipolar signal from a photodiode. I would like to create a DC offset on the output signal so that I can use the entire full scale of the ADC and not just the positive half.
I would like to know if I could create this offset by biasing the unused port with a DC source.
In section 9.3.2 of the LMH3401 datasheet it says, "In order to maintain proper balance in the amplifier and avoid offsets at the output, the unused
input pin must be biased to the same voltage as the input dc voltage, and the impedance on the unused pin must
match the source impedance of the driven input pin." This leads me to believe I could intentionally create an offset at the output by biasing the unused port to a voltage other than the DC voltage of my input signal.
Assuming this is a viable solution, I am considering applying this bias through a broadband bias tee to impedance match at high frequencies. What would be the consequences of poor impedance matching at low frequencies near DC? Is there a different, recommended way to apply this DC bias on the unused port?
Thank you,
Alex
