Instrumentation amplifier

Discussion in 'General Electronics Chat' started by mik3, Aug 1, 2009.

  1. mik3

    Thread Starter Senior Member

    Feb 4, 2008
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    Hi guys,

    Is it possible for the INA 129 instrumentation amplifier to work on 0-12V power supply?
     
  2. yourownfree

    Active Member

    Jul 16, 2008
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    I would say yes. looks like 4.5 volts minimum and 36 volts max.
    link for specs
     
  3. t06afre

    AAC Fanatic!

    May 11, 2009
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    You may check it out. But I do not know if the over-voltage protection will work. If it is any help I know Linear Tech. have Single Supply Instrumentation Amplifiers. Go to http://www.linear.com/ and search for "Supply Instrumentation Amplifier"
     
  4. AdrianN

    Active Member

    Apr 27, 2009
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    It will work, as long as the relative voltage differences between different pins is the same as in Fig 1 of the datasheet. However, there is a good reason why this is a a dual supply IC. Vref (pin 5) has to be connected to a low impedance point, otherwise the CMRR will be severely impacted. A ground connection assures close to zero ohm impedance.

    So, you can set Vref somewhere inside the 0-12V range and make sure you feed that point from a low output impedance buffer. You will have some CMRR degradation, as the buffer cannot have zero output impedance, but should not be severe. The signals will be referred to Vref (output signal, load, input signal).
     
    Last edited: Aug 9, 2009
  5. mik3

    Thread Starter Senior Member

    Feb 4, 2008
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    It will amplify only positive signals so I can connect Vref to ground.

    Is that right?
     
  6. t06afre

    AAC Fanatic!

    May 11, 2009
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    Yes I think so. But remember the common mode range specification. You may perhaps see some minor degradation compered to the data sheet specs. But this may not be important at all for your application
     
  7. AdrianN

    Active Member

    Apr 27, 2009
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    For a positive signal chain try the following: Connect your signal to pins 3 and 2, with the ground on pin 2. Pin 4 and 5 to ground. You should see your signal at the output. However, A1 output cannot go exactly to zero, because it does not have a negative supply. Your positive signal at pin 6 will be chopped off by 0.6V to 0.9V, because it will be pushed by A1 below ground. Some positive DC voltage on top of your signal should correct this.
     
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