• State TI Thinks Resolved
  • Locked Locked
  • Replies 3 replies
  • Answers 1 answer
  • Subscribers 46 subscribers
  • Views 840 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

ADS1299: Does the ADS1299 capture EEG signals require an external amplification circuit?

user5127672
Prodigy 20 points
Part Number: ADS1299

Hello TI engineers! I have recently encountered several technical problems with TI's chips. TI's evaluation board is to directly acquire EEG signals without an external amplifier circuit, but the EEG signal is a very weak signal, and the voltage amplitude is only uV level. The PGA of the chip has a maximum gain of 24, and if the EEG signal is 20uV, the amplitude after amplification is 20*24=480uV, so the voltage captured by the ADC is less than 1mV. My question is: Can EEG signals be  captured without an external amplifier circuit? Is an external amplifier circuit necessary? Do you have any suggestions? thank you very much!

  • 0
    TI__Guru 52982 points

    Hello,

    Thank you for your post and welcome to the forums!

    Yes EEG signals can be captured without an external amplifier circuit. Since the ADS1299 as an internal PGA and can measure signals at 1uV, a 20uV input signal with a gain stage of 24 should be more than enough to perform a measurement. Does your application require higher dynamic range than what is currently being produced?

    Have you verified the impedance of your electrodes? It could be that they are not properly connected causing a high impedance connection that limits your EEG signal. Typically you can reduce the impedance of the electrode by using abrasion or gel at the connection point.

  • 0 in reply to Alexander Smith
    Prodigy 20 points

    Hello, thank you for your reply! According to your experience, what is the general range of EEG signal amplitude? I remeasured the amplitude of the EEG signal about tens of millivolts. Is this normal? Many references describe the amplitude of the EEG signal to be approximately tens of microvolts. In addition, what is the difference between single power supplies  and dual power supplies for the ADS1299? Thank you!

  • 0 in reply to user5127672
    TI__Guru 52982 points
    Hi,

    Happy to help!

    The magnitude of the signal will be dependent on the type of electrode and gain settings in the signal chain. Similar to what your references have mentioned, tens of millivolts for an EEG signal is larger than I would expect. I would check to make sure that there isn't a gain somewhere in the signal chain that you are not back calculating for.

    In terms of performance, there is no difference between single or dual power supplies - they are simply there for convenience in power rail and measurement type options!