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Suggestion for Amplifier

farhan
Expert 1110 points
Other Parts Discussed in Thread: OPA192, OPA316, OPA365, OPA827, OPA172, OPA388, OPA320, OPA1611, OPA2322, OPA2354, OPA2320, OPA2388, LMV794, OPA2355, OPA2365, OPA360, OPA2356, OPA2350, OPA2316

Hi Everyone

I am working a device that measures frequency as well as Sound Pressure Level using a mic that has range upto 80kHz, I need to limit my frequency from 20 kHz - 80 kHz as well as amplify the incoming signal from mic by a factor 100.

Any suggestions, all amplifiers I came across with band limiting frequency are in audio range, did I miss any amplifier which works in ultrasonic range

Thanks & regards

Farhan

  • 0
    TI__Guru 60400 points

    Farhan,

    Any op amp with Gain-Bandwidth Product, GBP, of 8MHz willl have an effective bandwidth, BW, of 80kHz when configured in a close-loop gain of Acl=100 (BW=GBP/Acl) but you do not specify supply voltage or other requirements like input common-mode and output voltage range, precision, noise, etc.  If you use a single 5V supply, please take a look at OPA316, OPA320, OPA388 or OPA365; in case you look for a dual +/-15V supplies, please consider OPA172, OPA192, OPA827 or OPA1611.  To limit the bandwidth to exactly 80kHz, you may have to place a low-pass filter at the output of the amplifier.

  • 0 in reply to Marek Lis
    Expert 1110 points

    Hi Marek,

    Thanks for your quick response.
    Currently I am using TLC272CP as a zero cross detector, but its gain Bandwidth is 1MHz, I need a dual channel opamp with GBP 80MHz and after that I need low pass filter upto 80kHz ( currently I am using a RC network for that ).
    I came across this IC of yours OPA360AIDCKT which has capabillity of low pass filtering as well
    What I need to be more specific atleast dual channel opamp, of which one I need to use as Zero Cross detector and the another channel for amplification by 100 and then low pass filtering till 80 kHz
    Do you have any IC which does all of it or pair of IC's
    I need to measure SPL (dB) of the incoming signal from mic as well its frequency, if you have any IC catering to that, please let me know

    Thanks & regards
    Farhan

  • 0 in reply to farhan
    TI__Guru 60400 points

    Farhan,

    GBP of 1MHz is nowhere sufficient to obtain 80kHz usable bandwidth in a close loop gain of 100 but GBP of 80MHz is probably an overkill.  OPA360 has a fixed internal gain of 2 so you may not use it for your desired gain of 100. Most of our amplifiers do not have an internal filtering beyond first-order output roll-off due to normal bandwidth limitations that of course varies depending on a close-loop gain.  All of the op amps I previously recommended to you do have dual and quad versions - please take a look at OPA2316, OPA2320, OPA2322, OPA2388, OPA2350, or OPA2365.  However, if you really feel you need at least GBP of 80MHZ, you may also consider LMV794, OPA2354, OPA2355, or OPA2356.

  • 0 in reply to Marek Lis
    Expert 1110 points

    Thanks a lot Marek, your help is really appreciated.