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OPA381: Question about OPA381 photodiode biasing

Tim Sobering
Intellectual 860 points
Part Number: OPA381

Referencing a circuit like that in Figure 3 of the OPA381 datasheet, is there any reason I cannot tie the anode of the photodiode to a -10V bias instead of ground?  I understand I will have a higher dark current but I need to lower capacitance for the photodiode. 

  • 0
    TI__Guru 60610 points

    Tim,

    I don't see a problem with biasing the anode of the photodiode with -10V instead of ground as long as the reverse-breakdown voltage of the photodiode is above 10V.  Fig 4 shows a single supply application with +IN moved up to (V+)-1.8V, which effectively does the same thing as lowering the voltage on anode of the photodiode - see below.

  • 0 in reply to Marek Lis
    Intellectual 860 points
    Marek,

    I agree it shouldn't matter but I was just sanity checking myself. The diode I'm using has a maximum Vr of 35V. The only drawback to Figure 4 is the limitation on V+ (5.5 V max) so I cannot get the diode to a full 10V reverse bias and for my case 5 - 1.8 = 3.2V is not sufficient.

    Thanks for the quick response.

    Tim