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Op amp selection for 500KHz output and 125x gain

Hal Bowers
Prodigy 10 points
Other Parts Discussed in Thread: NE5532, OPA2613, OPA2614

I'm trying to reuse an existing board.  The prior application used an NE5532 where the first amp has a gain/lowpass filter and the second was just a buffer to invert the output.  It's good for 50KHz.

Need to swap out the amp with one that can get me 500KHz or as close as possible for different application.  First amp has R1=1K and R2=125k with 2.5pF cap for the highest gain setting.  The 1x gain setting uses 1 R2=1k with 300pF cap.  Any suggestions on a part the can output a 500KHz signal?  When no signal is present I need to the noise to be under 20mVpp.

I also need it to be in 8-PDIP package.

Any help would be appreciated...

  • 0
    TI__Genius 13935 points
    Hello Hal,

    I can research this for you, but in the meantime you may want to consider using our product selector tool.

    www.ti.com/.../high-speed-op-amps-products.page

    For 500kHz at 125x gain you will want an amplifier with over 125MHz bandwidth. We have many amplifiers that meet this specification. I would recommend using a smaller R1/R2 combination. I think the resistors will dominate the noise in this circuit.

    Some other parameters you should consider is voltage noise under 2nV/rtHz and offset voltage under 2mV (you will still need to trim the Vos). You may also want to look for low current noise.

    I ran some criteria through our selector guide and got the following two parts:
    OPA2613
    OPA2614

    These look pin compatible, do you need a power pad package?

    Here is the query if you want to tweak it:

    www.ti.com/.../high-speed-op-amps-products.page

    We do have higher speed amplifiers, if you select a faster op amp the broadband noise will increase unless you use a filter.

    Regards,
    Loren