# EEG Circuit Help

#### dotcomdotcom

Joined May 5, 2023
2
Currently working on an EEG design for an ESP32 microcontroller. This was part of my capstone project, and I am just working on this for fun and to learn more as this was my partners subsystem. I modifying my partners design which was originally on Multisim.
So the first image is the full EEG transient. Which I think the output it incorrect.

Next a notch filter AC sweep which is used twice for the 60 Hz noise.

I went back testing each component finding the differential gain and common mode of the instrumentation amplifier
Differential Mode Gain Ad = 100.4 mV / 1.04 mV = 96.5385 V/V
Common Mode Gain Ac = -489.32µ/0.9927 mV = 0.48932mV/0.9927mV = -0.4929 V/V
Common Mode Rejection Ratio (CMRR) = 20log10(Ad/|Ac|) = 45.8385 dB
This was interesting as in the datasheet for the IC it can reach 110 and I know ideally you want to be at least above 100dB

I am also planning on implementing a voltage regular for the negative 3.3V onto the instrumentation amplifier as the ESP32 can not take negative voltages but I am trying to perfect the amplifier first before so.

I also ran AC Sweeps on my bandpass filter, which I am trying to get the 3-12 and 12-30Hz frequency for alpha and beta waves.

Any advice on anything I'm doing wrong? Still trying to figure everything out and learn.

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#### ericgibbs

Joined Jan 29, 2010
18,225
Hi dot,
Welcome to AAC.
Please post your main asc file and any related models, we can then compare results.
E

#### Ya’akov

Joined Jan 27, 2019
8,512
Welcome to AAC.

The rules here limit the sort of help members can provide for coursework related questions to guidance based on your efforts. In order to ensure the nature of the question is clear, all such questions must be posted in the Homework Help forum. Your post as been moved here.

#### dotcomdotcom

Joined May 5, 2023
2
he rules here limit the sort of help members can provide for coursework related questions to guidance based on your efforts. In order to ensure the nature of the question is clear, all such questions must be posted in the Homework Help forum. Your post as been moved here.
Welcome to AAC.

The rules here limit the sort of help members can provide for coursework related questions to guidance based on your efforts. In order to ensure the nature of the question is clear, all such questions must be posted in the Homework Help forum. Your post as been moved here.