OPA858DSGEVM: OPA858DSGEVM

Hi Franck,

Few questions from my side-

• What is the expected photodiode capacitance?
• What is the expected TIA gain?

These parameters will be critical in deciding the TIA bandwidth.

Also, we have developed a TIA circuit design tool, where you can provide all the input parameters, and the tool will compute output parameters like TIA gain, Cf, rise time, and also AC and Transient plots, noise analysis, etc. Tool link: Analog circuit design studio. Please try the tool and let me know what you think.

Regards,
Aditya Gosavi

Hi Aditya,

CPD=10pF

I'm looking for a SPACE QUALIFIED device

Hey Franck,

Thank you for the details, will look into it and get back to you.

Regards,

Aditya Gosavi

HI Aditya,
Here is more inputs:
- Expected photodiode capacitance: It will depend on the reverse bias voltage, but it will be between 10pf and 200pF.
- TIA gain: The photoreceiver conversion gain shall be between 1500 and 2000 V/W

- The slew rate of the photoreceiver shall be greater than 2,000 V/μs.

Regards

Hi Frank,

Thanks for the information on capacitance and slew rate.

By TIA gain I meant to ask the value of Rf or feedback resistor that you are expecting to use in your TIA, basically the V/A conversion factor.

Regards,
Aditya

Hi Aditya,

Can I determined that by design? Actually I'm not able to find a device that is space qualified and as a GBW of 500MHz. (The photoreceiver 3-dB bandwidth shall be DC - 450 MHz.)
Regards,

Franck

Hi Frank,

As per your requirements, LMH6702QML-SP (1.7GHz, 3000 V/µs) seems to be the best fit. You can see in the tool image below with a Rf = 125 ohms, has a TIA bandwidth of ~500MHz.

Tool link: https://dev.ti.com/gallery/info/TIA/Photodiode_Circuit_Design_Tool_LMH6702QML/ver/1.0.0/

Let me know if you are interested, I can perform a TINA simulation of the TIA circuit, with details results.

Regards,
Aditya Gosavi

Hi Aditya.  Yes I will be interested in a TINA simulation of the TIA circuit with details results. Thanks a lot.