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OPA2192: Customer wants to know the parameter concerning about the noise

Sean Liao (Yu-Sheng)
Intellectual 2810 points
Part Number: OPA2192
Other Parts Discussed in Thread: OPA2188, , OPA192, OPA188

Hi sir, 

My customer has a few more question regarding the GBW Value of an Opamp.

              If I want my op-amp to be more endurance to Noise does this Value have any concern on this.

              And what about CMRR parameter of the Op-Amp.

              Does this value I still have to consider ??

 

              I’m tried to make a decision on which OPA I use OPA2192 or OPA2188.

  • 0
    Guru 318700 points

    What kind of noise?

    A higher CMRR protects against common-mode noise.

    For high-frequency noise that is above the amplifier's bandwidth, see the EMIRR (OPA2188 figure 38, OPA2192 figure 57).

  • 0
    TI__Mastermind 26088 points

    Sean,

    1. There are really two categories of noise to consider with amplifiers:  extrinsic, and intrinsic.  Extrinsic noise is noise from the outside world, and intrinsic noise is the noise generated by amplifiers themselves.
    2. For extrinsic noise CMRR, and PSRR are ways that noise signals can be rejected.  
    3. Intrinsic noise is the noise that is specified in the op amp data sheet and it is generated by the amplifier itself.  Intrinsic noise density tends to be lower when IQ increases.  It is also common that bandwidth increases with higher IQ.  Thus, it is common that noise density is often low for wider bandwidth amplifiers.  Now the total intrinsic nose at the amplifiers output is a factor of noise density and also bandwidth (i.e. Total_Noise = noise_density * sqrt(noise_bandwidth) ).  Thus, noise density can go down for higher bandwith amplifiers but the total noise will increase with wider bandwidth.  Thus, choosing a wide bandwidth amplifier (for low noise density) and limiting the bandwidth is a good way to get lower total noise.
    4. For extrinsic noise wider bandwidth provides the opportunity for more noise signals to pass.  For example, if the noise signal is at 1MHz and the amplifier bandwidth is 100kHz than the amplifier will attenuate the noise signal.
    5. In comparing the OPA2188 (8.8nV/rtHz, BW =2MHz), and OPA2192 (5.5nV/rtHz, BW = 10MHz).  You can see the relationship I mention in item 3.  In unity gain without any filter the total integrated noise for both would be:  Total_Noise188 = (8.8nV/rtHz*Sqrt(1.57*2MHz) = 15.6uV RMS, Total_Noise192 = (5.5nV/rtHz*Sqrt(1.57*10MHz) = 21.8uV RMS.  However, if you filter the OPA192 it can have lower noise because it's noise density is lower.
    6. Also, in comparing OPA192 and OPA188 from a noise perspective it should be noted that OPA188 is a chopper amplifier.  Chopper amplifiers have noise from the chopping calibration.  See https://www.ti.com/lit/wp/sboa586/sboa586.pdf for details on chopper amplifiers.
    7. Finally, details on intrinsic noise analysis are covered in TI precision labs.  See https://www.ti.com/video/series/precision-labs/ti-precision-labs-op-amps.html

    I hope this helps, Art