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Transimpedance Amplifier Selection

Dipto Moni
Other Parts Discussed in Thread: OPA657, LMH6629, OPA2350, OPA350, OPA637, DIP-ADAPTER-EVM

Hi,

I am designing a visible light communication receiver. As a part of of my design, I have decided to use either the OSRAM SFH213 or VISHAY BPV10 photodetector. The OSRAM SFH213 photodetector's typical photocurrent is 100-135 uA. The VISHAY BPV10 photodetector's typical photocurrent is 60-70 uA. I was wondering if anyone could help me pick a transimpedance amplifier, I couldn't find any. My receiver would be receiving data at 455 kHz. Thank you.

OSRAM SFH213 data sheet link: http://catalog.osram-os.com/media/_en/Graphics/00042727_0.pdf

VISHAY BPV10 data sheet link: http://www.vishay.com/docs/81502/bpv10.pdf

  • 0
    TI__Mastermind 22825 points

    Hi Dipto,

    I figure you would need a transimpedance gain of about 50kohm (50k x 60uA= 3V). For that gain, I'd use a FET input amplifier to minimize the impact of the inverting input noise current. OPA657 is one such device which has an input referred voltage noise of 4.8nV/RtHz and almost zero input current noise and plenty of bandwidth. If you figure out that you need less gain than what I have projected, you may benefit from a bipolar input device which has lower noise (0.69nV/RtHz) but has inverting current noise instead.

    Using about 14pF for CD (diode capacitance + device input capacitance), and GBP=1,600MHz for the OPA657 Gain Bandwidth product, you can expect a bandwidth of 19MHz (which is much higher than you needed anyway).

    To predict the output noise and SNR, compute IEQ from below (taken from the OPA657 datasheet) and multiply it by your 50kohm (or whatever it ends up being) gain:

    Hope this helps.

    Regards,

    Hooman

  • 0 in reply to Hooman Hashemi
    TI__Mastermind 22825 points

    Sorry I had forgotten to tell you the part number for the low noise (0.69nV/RtHz), high speed (4GHz GBP) bipolar device. That would be the LMH6629.

    Again, you would choose the LMH6629 for lower transimpedance gain (say below 10kohm).

    For both these device, you may end up throwing away some of the bandwidth to limit noise as you only need less than 1MHz.

    Regards,

    Hooman

  • 0 in reply to Hooman Hashemi

    Hi Hooman,

    Thanks for your reply. Your suggestions are great, but it would be helpful if I could find some pin through amplifiers.

     

    Thanks,

    Dipto Moni

  • 0 in reply to Dipto Moni
    TI__Mastermind 22825 points

    Hi Dipto,

    The closest low input noise current devices in PDIP packaging TI offers are shown below:

    OPA2350

    OPA350

    OPA637

    Regards,

    Hooman

  • 0 in reply to Hooman Hashemi

    Hi Hooman,

    Thank you very much. It looks like the OPA637 will work for me.

    Dipto Moni

  • 0 in reply to Dipto Moni
    TI__Intellectual 1165 points

    Hi Dipto,

    Just wanted to add that if you ever need to evaluate a surface mount device but need a DIP form factor, check out this handy tool to help with evaluation of 5 standard SM packages:

    http://www.ti.com/tool/dip-adapter-evm

    Best Regards,

    Marc