Tool/software:
Hello,
I find my TIA output is not correct.
And when I remove the input (so nothing connect to RF1), the output should be near zero. But one of my boards is 300mV and another is around 500mV (I forgot whether it's negative or positve).
There's some flux residue on RF1 and the offest gets lower to around 250mV after cleaning. So it seems there's still some leakage path?
Thanks for your help in advance!
Hi Follin,
There's some flux residue on RF1 and the offest gets lower to around 250mV after cleaning. So it seems there's still some leakage path?
I need additional information about your TIA application. They are:
1. What is your input current source parasitic capacitance?
2. What frequency are you converting I-to-V circuit?
3. What are the input current range? Is it a photodiode or something else?
4. Are you using switching power supplies for +/-5Vdc? What are L1 and L2 values?
OPA828 has larger input parasitic capacitance as its input. A better TIA op amp options may be OPA328, OPA320, OPA3S328, depending on your application.
https://www.ti.com/lit/an/sboa521/sboa521.pdf?ts=1749439376300
https://www.ti.com/lit/an/sboa284/sboa284.pdf?ts=1749476541364
There's some flux residue on RF1 and the offest gets lower to around 250mV after cleaning. So it seems there's still some leakage path?
I need the above the information to figure out what is going on. If you are using guard ring at the input of the op amp, the leakage current should be controlled somewhat. Yes, for the type of application, you need to clean the PCB board thoroughly with ultrasonic cleaning solvent and DI water, which it could be a possibility. Also, I need to understand if your circuit is stable for your application. You may also consider to implement T-network to reduce leakage current, see the above application note.
Best,
Raymond
