LMH32404: LMH32404 bandwidth

Hi Imon,

When using a balanced photo detector, you are sourcing and sinking current. The LMH32404 Ambient Light Cancellation (ALC) feature only works with photodiodes that sink the photocurrent. And the VOD pin is functional only when the LMH32404 device is used with photodiodes that sink the photocurrent. Also, the LMH32404 features two internal clamps; the fast recovery clamp is active when the photodiode is sinking a photocurrent while the soft clamp is active when the photodiode is sourcing a photocurrent.

Because the LMH32404 has features that are dependent on whether the photodiode is sourcing or sinking current, it may not be the most suitable for your application since your photodetector could be sourcing and sinking current. 

These two E2E threads discuss how to design a TIA circuit for balanced photodetection so I recommend reading through these:

https://e2e.ti.com/support/amplifiers-group/amplifiers/f/amplifiers-forum/1267024/opa657-device-recommendation-with-tia/4814120?tisearch=e2e-sitesearch&keymatch=%20user%3A572902#4814120 

https://e2e.ti.com/support/amplifiers-group/amplifiers/f/amplifiers-forum/1301340/opa818-reviewing-two-circuit-using-opa818-as-a-tia-and-opa843-as-a-op-amp 

If you are still wanting to use the LMH32404, knowing what the photodetector capacitance is along with the input current it provides will help to determine if a 100kHz signal can be supported by the LMH32404. I don't anticipate that being a concern, but I can confirm this if you are able to provide that information. 

Thanks,

Nick