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ONET1131EC: Peripheral component selection for monitoring photodiode of laser driver 'ONET1131EC'

Harvey Liu
Prodigy 30 points

Part Number: ONET1131EC

Hi TI technical Support Team,

          Good day! we are an electronic engineering team and have some questions about TI laser driver "ONET1131EC".

         According to the description in chapter 8.2.4, on page 37 of the specification,there is current mirror which is consist of BJTs and resistors for monitor photo diode.

       In general, BJTs are opearated at several MHz, which is feasible. However, this is a high bandwidth laser driver, I would like to confirm whether the current mirror is to monitor a CW laser for average laser power control.

Thank you,

Harvey

  • 0
    TI__Mastermind 42268 points

    Hi Harvey,

    The PD pin on this device is used to monitor the PD current, which measures the average laser power.  This can be used in a feedback loop to control laser power.

    Regarding the current mirror, as shown in Figure 48, its purpose is to enable PD to source current while maintaining positive voltage on PD pin.  Note in Figure 49, external current mirror is not present.

    Thanks,

    Drew