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Gain variation of op amp in high gain circuit

JerryL
Prodigy 210 points
Other Parts Discussed in Thread: LMV358, OPA333

Hi Team,

when using any normal op amp(LMV358 or OPA333) in the following circuits to amplify the low freq AC singals,   We know that the gain is accurate when Rf/Rin value is small, now Rf is 10Mohm and tend to be more larger.  what's the gain variation between devices? 

From the datasheet, open loop gain is provided in typical value practically, we understand it may have a little big variation cross parts. so for the circuit with very large gain created by huge value feedback resistor, how to evaluate the variation of gain?

Best Regards,

JH L

  • 0
    TI__Guru*** 139976 points
    JH,

    When the open loop gain approaches programmed gain then the open loop gain will be the gain. The output will also lag about 90 degrees.
    Distortion will increase because "extra gain" help reduce distortion. High gain leads to high output voltage which can lead to output clipping