LMH6629: Ultra small photodiode AC current amplification (2 MHz) using TIA

Hello Simon,

As I understand it you require help with the following topics:

- Selecting a gain-stage amplifier to go in-between the TIA and comparator stage

- Removing DC bias from TIA -> Gain -> Comparator chain

I can work on a simulation and recommend to you a circuit setup for this application.  When you use the term VLC, are you referring to visible light communication?

Please allow me time to build a circuit and check the stability of my design.

Best,

Alec

Hello Alec, 

Firstly let me thanks you a lot for your reply. You really not need to provide a solution it was more for asking a global advise if it is a good idea to go trough this solution by using Tia and then to amplify the output of the tia using different opamp stage while before I was directly connecting the TIA to the comparator.

For the DC bias I tough to use simply a high pass filter between the TIA and amplification stage or a DC servo to remove dc current. What do you think about this ? 

Thanks you for time and help for my question.

have a nice day,

Simon 

Hello Simon,

Yes, your solution with a gain stage between the TIA and comparator is a valid one to approach the design.

I have supported customers before using TIAs such as OPA855, OPA858, and LMH6629 as both a TIA and gain stage in signal chains.

I will check with my team on your question about removing the DC current.

Best,

Alec

Hello Alec, 

Thanks for your reply. I will try to design using OPA 855. For DC removal I ll really appreciate some advice on my proposal. 

Again thanks you, have a nice day, 

Simon 

Hello Simon,

I will take a look at an LMH6629 + OPA855 design.  Did you have a comparator selected?

Best,

Alec

Hello Alec, 

Firstly sorry for my late answer, I was abroad with limited access to TI forum. 

Actually I do not have. I tought to take a recent TI high speed comparator but didn't looked yet on it. 

Thanks you, 

Simon