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OPA2188: Output Behavior, when input voltage is higher than specification, such as 11.7V

Motoyasu Hattori
Genius 9205 points
Part Number: OPA2188

Hi,

My customer connected "OPA2188 output on Amp circuit (AMP)" with "OPA2188 input on Voltage follower circuit (VF)".

When OPA2188 supply voltage is ±12V, OPA2188(Amp) outputs 11.7V (typ).  However, OPA2188(VF) input is 10.5V (MAX).   What voltage does OPA2188(VF) output, if OPA2188(VF) input voltage is 11.7V?   Please advise us. 
Especially, we want to know whether this output is >10V or not.  Please advise us.

Thanks and best regards,
M.HATTORI.

  • 0
    Guru 140200 points

    Hi Motoyasu,

    section 8.3.3 of datasheet explains what happens.

    In any case you will leave the linear input voltage range of OPAmp and the performance of OPAmp may heavily degrade. You can easily avoid this by using a simple voltage divider at the input of voltage follower.

    Kai

  • 0 in reply to kai klaas69
    TI__Guru 62290 points

    The maximum input common-mode voltage of OPA2188 is 1.5V below Vcc - see below.

    Thus, I suspect your customer applies input voltage above 10.5V, which will result in the output collapsing within 300mV below positive rail (11.7V).