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TLV8544: AC Coupling after transimpedance pre-amp = then input to 10 bit ADC on MSP430FR2522

richard lowes
Prodigy 120 points
Part Number: TLV8544

Input is an IR Photodiode, receiving reflected pulses. 1st stage is a transimpedance - diode to ground,3meg feedback resistor. I would like to AC couple the next stage to try to ignore the ambient light signal. Any suggestions?

  • 0
    TI__Mastermind 24300 points
    Richard
    Here are some documents for you to review. Fundamentally I don't see any problem with your plan. AC-coupling for the second stage is common. You would still need to provide some DC bias on the secondary side of the ac-coupling capacitor. However, this would now be a controlled voltage and not a variable due to ambient light. another option if your IR communication is over a short distance, you can use a comparator. I attached a note on that option as well.
    Chuck
    www.ti.com/.../snoa988.pdf (this cookbook is for gas sensing but the gas sensor can be replaced by your photodiode).
    www.ti.com/.../snva808.pdf