AD8047

Hello vk19283,

Can you share what is the level or amplitude of your input signal when the issue happened? In addition, what is your load?

Best regards,
Paul

Hi Paul,

Thank you for responding. We used 2 op-amps in our setup, both as voltage followers. When operating each op-amp at +-6V supply, the input of the first op amp was 0V-5V square wave at 14Mhz. The load for the first op-amp was around 50 ohm. The input to the second op amp was a 12Vpp noisy sinusoid at 14Mhz. We left the output of the second op amp open. 

I can see how the 50 ohm load could cause problems. However, the second op amp seemed to have the same issue.

I appreciate your help,

Vinny

Hello vk19283,

Sorry for the late reply. You've mentioned that you have used 50-ohm load for the first op amp but I'm seeing a different load on your schematic, can you send here the actual schematic that you have used when you encountered the issue? 

One thing that I would like to ask is if you have used a dual-channel AD8047 on your setup. If this is the case, and you have used a 50-ohm load for the first op amp, there's a high possibility for the junction temperature (die temperature inside the IC package) to reach about 150°C (due to high power dissipation) which could cause parametric shifts that would lead to the 1st and 2nd op amp's issue.


Best regards,
Paul

Hello vk19283,

My bad, I just realized that AD8047 is only available in single channel. But the rise in junction temperature and power dissipation could still be the culprit why the first op amp ended up that way. 

For the 2nd op amp, can you share some scope shots of your output signal? Did you try using another probe in getting the output signal and encountered the same results?

Can you also share your real schematic? I'm sorry but I think what you're saying is not matching to the schematic that you previously sent. 

Thanks and regards,
Paul