Trans-impedance Amplifer with a Fully-Differential Amplifier

Question

I'm designing a trans-impedance amplifier (TIA) for a fairly fast Avalanche Photodiode (APD), to amplify pulses of 1mA that last few nanosecond. I found a solution that have just enough bandwidth with a single-output op-amp, but I want the output signal to be differential, and I haven't found any integrated TIA that meet my specifications.

I looked at several Fully Differential Amplifier (FDA), like the LMH5401, and designed a circuit close to that one:

^{simulate this circuit – Schematic created using CircuitLab}

I could not find any example of a similar circuit. While I can pick \$Z_{f+}\$ and \$Z_{f-}\$ to achieve the performances I want, I'm not sure how I should check my design.

1. How can I check that the circuit is properly balanced?
2. Does \$Z_{f+}\$ and \$Z_{f-}\$ have to be equal?
3. Is there any show stoppers that a SPICE simulation won't catch?

Answer 1

You can use a FET opamp, like OPA659 and then buffer the output with another opamp with differential output. Not sure if LMH5401 is adequate for TIA.

EDIT: Have you seen the OPA857?

Maybe you'll find useful this document

Answer 2

Texas Instrument made a reference design with a very similar circuit in December of 2017, using the LMH5401. It answers all my questions.