PRE-AMPLIFIER DESIGING FOR PHSIOLOGICAL SIGNALS OF ECG, EMG, EEG.

DIH SUMMER PROJECT

ABHISHEK KUSHWAHA 14024011 BIOMEDICAL ENGINEERING

Dr. SHIRU SHARMABIOMEDICAL ENGINEERING

INDIAN INSTITUTE OF TECHNOLOGY (BHU) VARANASI

SURENDRA MEENA 14024011 BIOMEDICAL ENGINEERING

Objective

To design a pre-amplifier with following characteristics

Low cost

Good noise removal ratio

Prototype for a compact design

Low power consuming

INTRODUCTIONWhy we need pre-amplifier ?

• To obtain weak physiological signals.• To obtain various noises free signals before final amplification.

BACKGROUNDDifference between ecg, emg and eeg signals

Preamplifier Design Stages

STAGE 1. An Instrumentation AmplifierSTAGE 2. Sallen key bandpass filters

STAGE 3. Notch filter

INSTRUMENTATION AMPLIFIER

Aim: Design a circuit that only amplifies the differential voltage – Common-mode voltage level remains unchanged

input buffer amplifiers Having high input impedance Low output impedance Infinity common mode rejection ratio Adjustable high gain

Gain =

Operational Amplifiers

LM 741 VS OP07 Electrical characteristics comparison with Data sheets

Noise In signals

Electrode contact noise, baseline drift and Electrode contact noise, baseline drift and motion artifacts.

EMG from the chest wall Instrumentation noise Electrosurgical noise

SOLUTION : Sallen Key filters

Power line interference

SOLUTION : Notch Filter

Filters

We use bandpass filter to remove noise in signal. Which is a combination of a high pass filter and low pass filter.

High-pass filtering with cut-off frequency at ~ 0.5Hz for ecg and 20hz for emg.

Low-pass filtering with cut-off frequency at 150Hz for ecg and 500hz for emg.

Sallen key filters with unity gain

Sallen Key High pass filter

Sallen Key Low pass filter

Notch Filter

To attenuate a particular frequency, 50 Hz supply. Twin T-Notch Filter

A Complete Pre-amplifier design

Thank You