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OPA2735

Viktor Bezrukov
Prodigy 10 points
Other Parts Discussed in Thread: OPA2735, OPA2188

OPA2735

Datesheet:

ELECTRICAL CHARACTERISTICS: VS = ・}5V (VS = +10V)

Boldface limits apply over the specified temperature range, TA = −40・・C to +85・・C.

At TA = +25・・C, RL = 10kΩ connected to VS/2, and VOUT = VS/2, unless otherwise noted.

What do imply yellow indicated phrase?

I have 100 ps OPA2735. Upper rail 4.15 V when Vs=+10

V

  • 0
    TI__Expert 6275 points

    This is a DC bias test condition which is a 10k load resistor on the output tied to mid supply and the output of the op amp driven to mid-supply. It is establishing that the DC operating point is at mid supply on the output and the 10k load will appear as a small signal load for AC characteristics since no DC current will be in the resistor since both ends of the resistor are at the same voltage. This is where the final test measures if the part meets the data sheet. Unless otherwise specified in the Test Conditions of a specific parameter in the specification table this circuit is used.

  • 0 in reply to Tim Green1
    Prodigy 20 points
    Hi Tim, I'm new at the forum. I have one question regarding the high input impedance of the OPA2735. The datasheet says only that, i.e. "high input impedance". No specification is given in tables (datasheet SBOS282B − DECEMBER 2003 − REVISED FEBRUARY 2005). Other OPAs, e.g. 2188 are rated 100MOhm/6pF. A fast search on google and this forum doesn't give me any results. Seems that is not estimated. Would you tell me the nominal value of that characteristic?

    Regards,

    Mariano Barella
    PhD student in Physics
  • 0 in reply to Mariano Barella
    TI__Guru 62700 points

    Mariano,

    Since op amps are meant to be used in close-loop configuration, you shouldn't have to warry about differential input impedance but only about common-mode input impedance - OPA2188 common-mode input impedance is around 6 Tera-ohm (6*1012 ).

    OPA2735 is a zero-drift CMOS op amp thus its common-mode input impedance may be comparable to OPA2188 - in the range of 1-10 Tera-ohm ( 1012  to 1013 ).

  • 0 in reply to Marek Lis
    Prodigy 20 points

    Marek, thanks for your fast and valuable response. To clarify, we are using it in closed-loop configuration, more precisely as a follower. I'm going to use those nominal values. Thanks again!

    Regards,

    Mariano