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INA114: Reference Pin Voltage

Harish Singh
Intellectual 995 points
Part Number: INA114
Other Parts Discussed in Thread: ADS1220, INA827, INA826, OPA202

Hi there,

I need a low cost alternate to AD8220 INA of Analog Devices. So, I'm planning to use INA114 to amplify the input signal with gain around 20 while the bipolar differential input signal will be in the range of 70µVp-p to 5mVp-p. I need minimum CMRR to be 100dB or 120dB will better on DC to 60 Hz with low offset voltage & drift.

My aim is to design a low cost Electromagnetic Flow meter.

Can INA114 be used as an alternate to AD8220?

If yes,

Since I'm using ADS1220 ADC and this doesn't allow me to pull out the internal band gap reference. Can I connect reference pin of INA114 (i.e. Pin No. 5 of 8-Pin DIP) package to a 1M resistor voltage divider with supply 5V (~2.5V at REF Pin with a parallel coupling capacitors of 10µF & 0.1µF for noise suppresion)?

else,

Can you suggest me good low cost alternate INA?

You can visit  for brief detail of my application.

Thanks & Regards,

Harish

  • 0
    TI__Guru 60570 points
    Harish,
    INA114 should work as an alternative for AD8221 from the technical aspects but NOT from the pricing point of you - it's actually more expensive.
    If you need a low cost alternative to AD8221, please review INA826 and INA827 datasheets.
  • 0 in reply to Marek Lis
    Intellectual 995 points

    Hi Marek,

    Thanks for the quick response.

    INA826 looks good. Can you suggest the circuit diagram for INA826 with component values if possible for my application.

    The AD has given a reference circuit for the same purpose as following. May be it will help to suggest a solution to my problem.

    AD has connected the reference pin of AD8220 to ADC IC's band gap reference. But ADS1220 do not have the option to pull-out its internal reference to any pin. So, how & where should I connect this pin for ultra low noise? Can I connect reference pin to a 1M resistor voltage divider with supply 5V (~2.5V at REF Pin with a parallel coupling capacitors of 10µF & 0.1µF for noise suppresion)? or I should use something else? The option should be a low cost.

    Thanks & Regards,

    Hsrish

  • 0 in reply to Harish Singh
    TI__Mastermind 23050 points

    Hi Hsrish,

    You can not drive the reference pin of the INA with a voltage divider. Internally, the pin is the reference of the difference amplifier, and a voltage divider will alter the characteristics of the diff amp. You must drive the reference pin with a low impedance source, such as an LDO or the output of an op amp. I have attached a schematic that buffers a voltage divider using an OPA202 as an example. You will have better noise performance if you use smaller resistors, but you will also consumer more power in the divider. You can use the attached simulation file to approximate the noise performance and balance this with your power consumption.

    INA826 ADC Drive.TSC