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Original question:

OPA2188 temperature vs. bias current

OPA2188: Input bias current and CMRR

Gerardo Tadeo de la Garza Mora
Prodigy 380 points
Part Number: OPA2188

Dear  amps team,

could you tell me the following:

What is the value of the Ib when TA = -20 to +85°C? on the DS there's a plot (figure 8), but I would like to have the actual value.

CMRR is mentioned on the DS, but is the follow available: what is the CMRR (V-)+1.5 to (V+)–1.0?

thanks!

Tadeo

  • 0
    TI__Guru 60570 points

    Tadeo,

    IB in OPA2188 is the sum of two independent components: current leakage of ESD/EOS protection structures and current generated by the chopping action of the front-end switches.  The typical chopping current is around 160pA (max 850pA) and it is more less constant over temperature.  The maximum leakage current at 125 deg C is around 18nA and since it doubles every 10 deg C, this means at 25 deg C it's around 18pA.  Therefore, the maximum IB at lower temperatures is dominated by the chopping current (max 850pA) and at the higher temperature (~80 deg C) leakage current becomes the dominant - see below.

  • 0 in reply to Marek Lis
    TI__Prodigy 380 points

    Thank you Marek!

    What about the CMRR, do we have information on the mentioned range?

    Best regards,

    Tadeo

  • 0 in reply to Gerardo Tadeo de la Garza Mora
    TI__Guru 60570 points

    Tadeo,

    Since the CMRR is specified in the datasheet over entire temperature range from (V-)+0.5V<Vcm<(V+)-1.5V (see below), this covers (V-)+1.5 to (V+)–1.5 range.

    However, input common-mode voltage closer to positive rail than 1.5V, Vcm>[(V+)-1.5V], will caused a non-linearity in the input differential pair resulting in large increase in the input offset voltage (thus decrease in CMRR=ΔVcm/ΔVos) and for that reason is not guaranteed.