transimpedance example here

from above video

I need to design a trans-impedance amplifier to amplify the signal from a photodiode to make a PPG sensor I need a signal to acquire from the wrist.

photodiode I am going to use is SFH 7060

I don't understand how to connect anode and cathode of SFH 7060 to the amplifier input pin.

is it as follows?

connect pin 6 of SFH 7060 to (photodiode anode) inverting input of opa170? and connect pin 7 to GND

do I need an instrumentation amplifier for this?

SFH 7060 data sheet from data sheet

  • \$\begingroup\$ hat are you doing with the photodiode? Using it in photovoltaic mode, or reverse biased for maximum sensitivity and highest speed? \$\endgroup\$
    – user16324
    Jun 4, 2020 at 12:53
  • \$\begingroup\$ @Brian Drummond I don't understand those keywords. can you explain in an answer, please. how should I proceed to get maximum sensitivity from the mentioned sensor? \$\endgroup\$
    – komto909
    Jun 4, 2020 at 15:38

1 Answer 1


Photo-current flow in the opposite direction to standard diode forward current so, if you want the op-amp output to rise when photo-current flows, you connect the anode to ground. If you want the op-amp output to fall when photo-current flows, you connect the cathode to ground.

Vout will rise in the schematic below when light hits the photo-diode: -

enter image description here

Equivalent circuit of a photodiode from here: -

enter image description here

  • \$\begingroup\$ dummy question how photodiode get energy? without supply voltage? \$\endgroup\$
    – komto909
    Jun 4, 2020 at 11:34
  • 1
    \$\begingroup\$ From the light itself exactly the same as a solar cell. \$\endgroup\$
    – Andy aka
    Jun 4, 2020 at 11:35

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