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OPA2187: Ibias offset tolerance at 50℃

Part Number: OPA2187

Tool/software:

Hi teams,

I would like to ask you do you have date of Ibias offset tolerance at 50℃ on OPA2187?

I would be design for next model and I will use OPA2187.

On this calucilation about circuit tolerance, I need above information.

Do you have data as below picure?

Or, do you have similar date as that one?

Best regards,

Tomo Akiyama

  • Tomo,

    1. We do not have a measured histogram for IB at 50°C.
    2. It is possible to calculate this based on the room temperature limits.  The input bias current is actually the leakage of the input ESD diodes.  The diode leakage has a known relationship.  It increases by a factor of 2x for every 10°C increase in temperature.  Thus, you can calculate the bias current using the following relationship:  IB(T) = IB(125°C)/2^[(125°C - T)/10].  The document Optimizing Chopper Amplifier Accuracy describes this in more detail and also provides an example calculation for 100°C.  You could use that relationship on the typical or maximum limits to estimate the limit at any temperature.
    3. Be careful about focusing on IB as an error source for chopper amplifiers.  Chopper amplifiers have a DC IB and a transient IB.  The DC IB is generally very low as with most CMOS devices (in the picoamps ).  The transient IB can be large (in the microamps).  The IB specified in the data sheet is the DC IB.  The transient IB has very narrow transient spikes (see figure 3-5) in the chopper document linked above.  When these transients interact with source impedance or feedback impedance they generate a transient voltage.  The transient voltage can be consider as a noise source, but also introduce a bias-current input offset voltage (see section 5 in the document).  The error introduced by the transients generally is larger than the error from the DC bias current. The exception to this is at higher temperature where the DC IB can be significant (approaching nano-amps). 
    4. The best way to minimize error due to DC bias current and bias current transients in a chopper amplifier is to limit your source impedance to the acceptable maximum source impedance documented in table 5-1.

    best regards, Art

  • Adding to Art's comments, up to around 80 deg C, the current from chopping action of the front-end switches dominates the total IB while above 85 deg C reverse bias leakage current of ESD diodes becomes a dominant source of IB. For this reason at 50 deg C, IB distribution would be similar to its room temperature distribution and based on the max IB of +/-350pA could be represented by the following histogram. 

  • Hi Ark, Marek,

    Thank you for your reply.
    It is very helpful for circuit design.

    I appriciate your kindly support!

    Best regards,

    Tomo Akiyama