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ECG Amplification

Tejaswi Kakarna1
Prodigy 20 points
Other Parts Discussed in Thread: INA2126, INA126, INA326, INA333

Everyone,

I'm trying to built a ECG amplifier using INA2126P it is a dual pin configuration and the input is 5mVPP I have built the basic circuit, in order to get the gain 1000 I kept Rg as 80 and also gave the power supply as +/- 5V to both positive and also negative. the output I'm getting is in microV can anybody please tell me what I need to do in order to get proper output. In the specification detail it is said that we need to add extra sense connection I dint get that point, what kind of sensing should be done.0820.ina2126.pdf

I have also kept load resistor as 25Kohm

  I'm a grad student not so perfect in designing but any help is appreciated.

I have attached the specification sheet for INA2126P

Thanks in advance

Tejaswi

  • 0
    TI__Guru 64345 points

    Hello Tejaswi,

    First, to learn more about designing ECG systems with precision amplifier products please utilize the repository of information present on this forum and search through the numerous posts on ECG designs using other amplifiers and perhaps this one too. 

    Since you're not getting any signal out of the amplifier my guess is that you have something connected incorrectly.  Please recheck your circuit connections and provide us a schematic of your configuration of the INA2126 showing all connections to the inputs and outputs.  Be sure to include local decoupling at the power supply pins, 100nF will work well.

    Regards,
    Collin Wells
    Precision Linear

  • 0
    TI__Mastermind 25865 points

    Hello Tejaswi,

    Thanks for your interest in using hte INA2126P for your ECG application.  With +/-5V supply, 5mV differential input voltage, and gain of 1000 the INA126 will be limited by the output swing.  I'm assuming your input common-mode voltage is 0V.  Please see the graph in the lower right corner of page 4 of the datasheet (Input Common-mode Voltage Range vs. Output Voltage).  Nonetheless, the output you measured should be 4.1V-4.25V instead of uV.

    Therefore we will need to see your schematic.  Please post it to the forum.

    Concerning the sense connections, the datasheet states that if you're using the dual version you need to connect the output of each amplifier to the corresponding sense pin.  This means for channel A you have to connect pin 6 to pin 7.  For channel B you have to connect pin 10 to pin 11.

    On a side note I suggest searching the forum for ECG.  There are a plethora of posts that have schematics and other implementations that use devices such as the ADS129x, INA326, INA333, etc.  I think this is the first post using the INA2126 for ECG.