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TLV274, Common mode input voltage range

YILMAZ KIRÇİÇEK
Intellectual 905 points
Other Parts Discussed in Thread: TLV274, TLV2374

Hi,

TLV274 common mode input range is Vdd - 1.35V as datasheet. TLV274 is RRO opamp. But we used it as RRIO opamp and did not experience any problem.

We used +-5V split suppy. I can measure excessive commom mode voltage on device pins. But everything seems working properly.

TLV2374 is pin compatible with TLV274 and it is RRIO but gets $0.30 extra cost. (totaly 5*$0.30)  I can use TLV2374 but do I realy need to replace ?

Everything seems ok but I can not able to be sure. I can measure 4.87V and it is slightly higher than 5-1.35V. 

Does anyone have an idea ?

 Regards.

  • 0
    Prodigy 30 points

    Hi YILMAZ,

    my answer from germany is not so good in english, but have a look upon the input stages of the tlv274 versus the tlv2374. the tlv274 has only a jfet (n) in differencial configuration (2 transistors), while the tlv2374 has a complementary nMOS/pMOS build with two differential transistor pairs (4 transistors). you can drive both against GND and against VDD, but the jfet works nonlinear nearer the VDD-level and can be driven down under GND. take sure, that the input current will be inside the absolute safe maximal operation area of cmr of typical 10 mA. if you are not sure of the input current, you can limit with a resistor serial to both inputs to limit the bias current. a negative affect is the takeover of the tlv2374 the two differential transistor pairs begins commonly conducted in a crossover-level, the jfet-input never knows those distorsion in crossover. in some cases (with led as light-sensor e.g.) with very low sensor-current is to detect, the two differential transistor pairs can source or sink bias-current into/recursive out of the input transistor.

    make many tests also with other opamps cause you can not see by any datasheet how an opamp will work specialy over the cmr you have chosen to the output-stage of the circuit/measurement/sensors at the inputs of the tlv274/2374.

    the maximum differential input voltage of both opamps is ±VDD respectly -VDD to +VDD without damage the input stages.


  • 0 in reply to Klaus Thiesler15671
    Intellectual 905 points

    Good moning Klaus,

    Thank you for your answer.

    Referring model given in TLV274 datasheet, using this opam as voltage fallower with 4.8V input seems impossible, however I test, it can be but I could not able to understand how ?

    Best regards.