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TLV2772: Why does my summing amplifier not work?

Prodigy 80 points

Replies: 5

Views: 336

Part Number: TLV2772

Dear Sir/Madam,

I build a summing circuit for my piezoelectric microphones with TLV2772, which is shown below.

However, it does not work.

The output voltage after summing is smaller than that before summing (Vout is smaller than V1 and V2).

I also tested the summing part with function generator (V1 and V2 were provided by function generator), but it did not work (Vout is a little bit higher than V1 or V2, but much smaller than V1+V2) .

Why does this happen? How can I solve the problem?

Please help. Thank you very much.

Best, Hai

  • Hi Hai,

    what is the supply voltage? What is the input signals' amplitude? Are the input signals dc-coupled or ac-coupled?

    Kai
  • In reply to kai klaas69:

    Hi Kai,

    Thanks a lot for your quick reply.
    The supply voltage is 5V.
    The input signal amplitude is around 5mV.
    The input signals are AC coupled.
    I also tried OPA337. But it did not work.

    Best, Hai
  • In reply to Hai Liu50:

    Hi Hai,

    the output of TLV2772 cannot go negative with a single supply voltage. So, this will not work.

    So, either you take a bipolar supply voltage of +/-2.5V or you provide a suited bias voltage of arround midsupply like shown in figure 62 of datasheet of TLV2772 or figure 6 of datasheet of OPA337.

    Your circuit could look like this (picture is from another thread):


    Kai

  • In reply to Hai Liu50:

    Hello Hai,

    It looks like Kai has answered your question. Let us know if you have any more issues. Otherwise, we will assume your issue has been resolved and consider the thread as closed.

    Thanks,
    Daniel
  • In reply to Daniel Miller56:

    Kai solved my problem. Thank you guys!

    Best, Hai

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