ADA4807-1 had output oscillation on Non-inverting Topology

Hi Klex Lin,

ADA4807-1 is a 180MHz, 1mA supply current device. You should make sure you're doing a high frequency layout board (ground plane, short leads, etc.) to avoid creating excessive parasitics that would cause oscillations. Also, I recommend you lower your feedback from 15k to avoid creating phase shifts from this large resistor and any parasitic capacitances you may have. You can lower RF to 2k (and RG along with it) to see.

It may help to eliminate the 6k in series with your non-inverting input. There is significant input bias current (uA) that won't work well with such large resistor. You may also want to load the output more heavily (say 500ohm) to see if that helps. Also, when probing with a scope, make sure you have some resistive isolation to the ADA4807-1 output pin (to avoid scope capacitance giving you issues). May want to use the scope 50ohm terminated input as a way to measure instead of a scope probe.

Regards,

Hooman

Hi Klex Lin,

Also, please make sure that if the generator that you've shown (V2) is at a distance from the ADA4807-1 stage and there is an interconnect (coax) cable involved, that the generator impedance (50ohm for most lab generators) is terminated in 50ohm near the ADA4807-1 stage before going to the non-inverting input. If you have a coax interconnect and you're not terminating it near the stage, that could be an issue in your setup.

Regards,

Hooman

Hi Hooman,

I change RF to 1.5K ohm (and other R along with RF) and clear path issue between source generator & non-inverting input. The oscillation issue of ADA4807-1 had been solved. I really appreciate your support.

Best Regards 
Klex Lin

Hi Klex Lin,

That's great that a lower RF resistor resolved your oscillation issue with ADA4807-1!

We all need some good news these days.

Regards,

Hooman