AD4807-1 Oscillation

I have a amplifier+filter signal chain comprised of AD4807-1 opamps. Singled ended supply of +3.3V & reference of 1.65V.

My original simulation was done with TINA-TI and didn't see any problems, but now that I've got the prototypes back, I'm getting a ~12-13MHz oscillation on the output of the first amplifier stage. I tried to re-run my TINA-TI simulation and wasn't able to get it to run fully. Possibly the original simulation was suspect.

I re-drew it up in LTSpice (attached) and do observe a ~35MHz oscillation in simulation with no input signal. Any ideas on how I can resolve this?

Thanks!
  • 0
    •  Analog Employees 
    on Nov 17, 2020 12:52 AM 2 months ago

    Hi,

    I have checked the attached schematic and checked the oscillation and it is present even I removed most of the blocks and left the 1st block after the STAGE_ONE node.

    I tried to understand what type of filters you have in the circuit.
    From the input, you have used band pass filter.
    You have also multi feedback filters on the middle blocks.
    But I am not sure what type of filter you have on the 1st block and last block.

    Maybe it would be helpful it you can tell us more about your application. What is your target bandwidth of interest and input signal level and desired output.

    Thanks and regards.