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OPA1S2385EVM: PCB Layout Question

Part Number: OPA1S2385EVM

My question about the OPA1S2385EVM is about the PCB layout of some of the parts. Most of the critical parts have "Void" areas underneath them on the other side of the PCB. Is this to reduce leakage current?  What is the purpose of these void areas?

Is this common practice in transimpedance amps? Does it make a significant difference?

 

 

 

  • Hi Matt,

    The purpose of cutting out metal underneath the parts is to reduce the board parasitic capacitance at both the input and output of the device. It does help in making the circuit more stable, when working with a low source impedance like 50-ohms.

    For trans-impedance applications, the GND metal underneath the part adds additional board parasitic cap at the photo-diode input which could both slightly reduce the overall BW and increase the noise gain of the part at higher frequencies. Cutting out the metal beneath the input pins helps get back those extra bit of performance.

    Best Regards,
    Rohit