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OPA857EVM component configuration

Urs Utzinger
Prodigy 10 points
Other Parts Discussed in Thread: OPA857EVM, OPA857

I received OPA857EVM and the mounted components slightly differ from the configuration mentioned in the manual.

The following resistors are not installed: R4, R16, R13, R14, and R9, R10 I believe are missing also. 

I would like to know if that is standard shipping configuration. 

Since the evaluation board I ordered produces no output in test configuration, I wonder if I have a faulty product that was not fully assembled or tested. I understand that the board should work without those resistors in place.

  • 0
    TI__Genius 12631 points

    Hello Urs,

      There is a typo in the schematic which shows R4 twice. The true R4 is the series resistor between pin 15 and J2 SMA. This should be uninstalled.

    R16 - It doesn't matter if this is installed or not since the jumper JP2 will set the transimpedance gain.

    R13 and R14 - These should be uninstalled on the board.

    R8 and R9 -These should be uninstalled on the board.

    R10 and R11 -These should be installed on the board and should be 0 ohm resistors. Please double check this. They should be connected to the transformer terminals.

    Are you applying a signal to the Test In input? You cannot apply a signal to the Vin input unless you install  R4 between pin 15 and J2. The default configuration of the EVM is to test the OPA857 in test mode. The user guide of the OPA857 describes how to configure and test the OPA857 in test mode.

    -Samir