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OPA1652: Comparison of OPA1652 and LF353

Marzieh Karami
Prodigy 190 points
Part Number: OPA1652
Other Parts Discussed in Thread: LF353,

Tool/software:

Hi,

We have a legacy design with a differential mode op-amp that uses LF353. We have high CM noise input to the differential circuit and we only care about DC input. Do you think OPA1652 is a good replacement? What factors should I consider given that it should work in high noise environment?

Thanks,

Marzi

  • 0
    TI__Mastermind 22590 points

    Hi Marzi,

    Yes the OPA1652 should be a better fit considering the CMRR spec is a typical of 110 dB. Also the input bias current is a typical of 10pA on the OPA1652 vs 50pA on the LF353. This improvement of Ib will help with reduce the voltage noise created by ib times source impedance. The OPA1652 also has better input voltage and current noise. Given the CMRR specification improvement alone I believe this will a noticeable improvement. 

    I hope this information is useful. Let me know if I can be of further assistance or expand further on the topic. 

    Best Regards, 

    Chris Featherstone

  • 0 in reply to Chris Featherstone
    Prodigy 190 points

    Thanks Chris. What about GBW - gain bandwidth product? It seems like OPA1652 has  a GBW of 18 Mhz whereas LF353 has 4 Mhz. Does not this mean it will be less stable?

  • 0 in reply to Marzieh Karami
    TI__Mastermind 21017 points

    Marzieh,

    I will jump in here for Chris as he and most of the staff are on a US holiday.  The additional gain-bandwidth product will not make the device less stable.  Stability generally relates to capacitive load or capacitance on the inverting input of the amplifier.  If you don't have a large capacitive load, you should not have a stability issue.  Figure 29 in the OPA1652 data sheet provides detail on how capacitance value effects the phase margin.  Generally you want phase margin of 45 deg.  The LF353 doesn't provide this info as it is an older data sheet.  Having a larger GBW is usually though of as a benefit as it allows for higher gains while still maintaining the bandwidth.  If I missed your point, Chris will return on Monday to support follow up questions. 

    Best regards, Art

  • 0 in reply to Art Kay
    Prodigy 190 points

    Thanks Art. I will calculate my phase margin with both of the op-amps then.

  • 0 in reply to Art Kay
    Prodigy 190 points

    Are tina models for both correct in terms of bandwidth and phase shift?

  • 0 in reply to Marzieh Karami
    TI__Mastermind 22590 points

    Hi Marzieh, 

    Yes the simulation looks correct. I was able to replicate Figure 5 from the product datasheet below. 

    sbom737c.TSC

    Best Regards, 

    Chris Featherstone