Hello,
I need to convert a 1Vpp bipolar differential signal with 1V input common mode voltage to single-ended with 80MHz flat bandwidth and 2x gain using +3.3V . Can you suggest a good configuration using the LMH6629 (or select a different part)?
Thanks, John
Hi John,
I think you need a "difference amplifier" to do this, similar to what is shown below:
http://en.wikipedia.org/wiki/Differential_amplifier
A single 3.3V supply would not allow your output to swing below ground. You have to think about creating a reference potential so that the output of your stage is sitting at this reference level. Things would be easier, for biasing, if you can AC couple your signal to this difference stage through R1 and R2. If you AC couple into R1, and R2, then your reference potential gets tied to Rg bottom (instead of ground) and that would be the voltage DC level at the output which allows symmetrical and undistorted output swing.
Or, if you need more balance between the inputs, you could go with an instrumentation amplifier setup, as shown:
http://en.wikipedia.org/wiki/Instrumentation_amplifier
From the specs you've described, I think you'd have a wide selection of parts that can fit your needs. I would not use the LMH6629 here because it requires a minimum stable gain of 4V/V (or 10V/V depending on the COMP pin voltage applied):
Selguide selection results:
Regards,
Hooman
