LED Control Via Opamp

Hello Neeraj,

Can you share more details regarding your application?

How much gain is needed?
What bandwidth has to be achieved?
And what is the highest noise that can be tolerated?

from the input standpoint (considering the forward voltage and forward current), AD8009 can accomodate the said photo transmitter but we need to consider other factors stated above to properly determine if AD8009 can fit on your application.

Thanks,
Kenneth

Hi Kenneth11, Thanks for your response. 

Gain= 2

BW= 155 MHz

Hi Neeraj,

As checked, AD8009 can accommodate your desired gain and bandwidth. Just pay attention to the feedback resistance that you are using as gain and BW for current feedback amplifiers are tightly coupled. On the specs table of the datasheet, recommended resistors are stated. You can also check the performance characteristics plots (TPC 2) on page 5 of the datasheet and TPC 15 (transresistance plot for TIA applications) on page 7.

Feel free to reach out if you need further help on your application.

Best Regards,
Kenneth

Hi Neeraj,

As checked, AD8009 can accommodate your desired gain and bandwidth. Just pay attention to the feedback resistance that you are using as gain and BW for current feedback amplifiers are tightly coupled. On the specs table of the datasheet, recommended resistors are stated. You can also check the performance characteristics plots (TPC 2) on page 5 of the datasheet and TPC 15 (transresistance plot for TIA applications) on page 7.

Feel free to reach out if you need further help on your application.

Best Regards,
Kenneth

From the FPGA Spartan7, I am providing LVDS input. A4 is the positive differential signal, and K4 is the negative differential signal. is this correct?

Hello Neeraj,

Your circuit is correct since you are using the SOIC package. In cases where you need to add a feedback capacitor for stability, please check this article (Compensating Current Feedback Amplifiers in Photocurrent Applications | Analog Devices) to determine the proper value of Cf to be added. Wrong values of Cf can make the output of AD8009 oscillate since it is a current feedback op amp.

Best Regards,
Kenneth

Thanks, kenneth11

Your're welcome. Feel free to reach out for additional help if needed.

Hello,

It appears that the above question has been answered already so I'm temporarily closing this thread. In case there are additional questions, feel free to reply to this thread. Thank you!

Best regards,
Paul