Im working on an IR sensor based off of the Texas Instr. particle sensor (TIDA-00378). They use just one photodiode in their design. I would like to use multiple photodiodes, lined up with multiple emitters, to cover a larger area. In my current design using phototransistors, I was able to connect multiple phototransistors in parallel to achieve this, as shown in the second image. Will this work similarly with the differential amplifier if I use multiple photodiodes in parallel?


Block Diagram of Particle Sensor

My current design

  • \$\begingroup\$ @Hearth ty youre right. reworded. \$\endgroup\$ Feb 1, 2019 at 22:57
  • \$\begingroup\$ Will the system be more sensitive? Yes. Will you be able to guarantee that it's exactly x4 sensitive? No. You are effectively increasing die size by paralleling but you can't guarantee that characteristics of each die are matched. Also, your response BW will probably decrease as you will now have more C.Why not just use a photodiode that's larger/more sensitive? \$\endgroup\$
    – EasyOhm
    Feb 1, 2019 at 23:03
  • 1
    \$\begingroup\$ @Gonzik007 I am trying to cover a small 2d plane of detection area. A "laser wall" of sorts. \$\endgroup\$ Feb 1, 2019 at 23:09
  • \$\begingroup\$ Would a lens to focus light down to just one photo-diode be possible? It would avoid all the circuit complications mentioned in the above comments. \$\endgroup\$
    – user105652
    Feb 1, 2019 at 23:55

1 Answer 1


Yes you may put as many PD’s which are current sources to add together like a PV panel array in series /parallel.

But will the optical sensing work? Not unless they are all blocked SNR of detection depends on this contrast ratio for all currents combined and 0.5mA/mW received typ. And SNR directly affect detection error rate.

So a good wall of laser light must be defined in terms of threshold for logic levels in current, then converted to voltage with R using a TIA with gain. Optical gain may be achieved with lenses or series strings of narrow emitters or . ??? So this must be defined in the question with the optical path spacing and length, with the size of the object anywhere typ. from 1mm to 1m in size., as well as velocity or time interval for detection.


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.