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INA240: conversion of differential inputs to single ended with appropriate offset

Arun Kumar
Expert 1030 points
Part Number: INA240
Other Parts Discussed in Thread: REF2033, INA500, INA170, INA132

Tool/software:

Hello experts,

We are looking for a (preferred)single chip solution , which does the following, with one major change.

The differential inputs, instead of measuring a shunt resistor are coming from a sensor , which outputs +- 2v.

This +- 2v has to be converted to 0 to 3 v.

We have VREF of either 3.33v or 1.65v coming from a reference IC(REF2033)

Is there a similar amplifier with a unity gain and REF1, REF2 pins available to add appropriate offset?

I tried looking up similar differential opamps but those that have unity gain don't have REF1, REF2.

Kindly help

Thanks in Advance ;)

  • +1
    Guru 294210 points

    The INA170 allows this. But it would be cheaper to use a plain difference amplifier like the INA500 or INA132. (All of them have a single reference input.)

  • 0 in reply to Clemens Ladisch
    TI__Mastermind 31570 points

    Hi AK,

    The unity gain diff amps suggested by Clemens are probably the best fit for a single-chip solution for this purpose

    Regards,

    Guang

  • 0 in reply to Clemens Ladisch
    Expert 1030 points

    Thanks for the reply.

    Yes, The INA500B is the best choice , with a reference of 1.65v , i can get +2.05v to - 2.05v differential scaled up to +2.67v to 0.625v single ended which is close enough.

    One other thing, I have an application requirement of a maximum differential input frequency of 1Khz , with addtional high frequency switching component injected from a 20 KHz switching source.

    I see the bandwidth of the INA500 is 125 KHz, could you please confirm if this bandwidth is enough for my application requirment?

  • 0 in reply to Arun Kumar
    Guru 294210 points

    Figure 6-35 shows that 20 kHz signals will get through:

    But I doubt that the switch noise is a sine wave. Higher-frequency components will be attenuated.

  • 0 in reply to Clemens Ladisch
    Expert 1030 points

    Thanks Clemens! It is clear now.