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BME 140 Review

Michael Klopfer

3/17/2014

Disclaimer: I do not know the exact problems onthe finalthis session will cover major concepts

that I believe are important to your success on

the exam, it is not meant to be a comprehensive

review!

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Offset NullificationA good approach

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Offset NullificationAn alternative (typically not as

good approach)

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Offset NullificationAn alternative (typically not as

good approach)

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Offset NullificationAn alternative (typically not as

good approach)

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Offset NullificationAn alternative (typically not as

good approach)

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Know this circuit, be able to prove it for the exam!

The trick is knowing how to apply kirchhoff's laws for

the coupled non-inverting amplifier at the input

Why are the gains set as they are?

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Why all the leads?

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ECG Leads and Electrical Axis

Ground

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The Heart acts as

a charge pump

This model is used to show the reason why thee leads

show the values they do when differentially amplified

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Interesting Key Point

KNOW THIS!

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Estimating the Cardiac Vector Direction

How can you estimate the cardiac vector by just

knowing the lead voltages? Remember for

(LEAD I, LEAD II, and LEAD III), only 2 leadsare linearly independent, in the set -- the 3rd is

linearly dependent on the other two

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There are several geometric tricks to

calculate/estimate the cardiac vector (either

instantaneous or mean) See class notes or

Watch this video:

https://www.youtube.com/watch?v=jg5X3V5I

PS4

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Left Anterior Descending [LAD] (The

Widowmaker)

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Other Discussed Topics:Destruction of heart anatomy and different contraction patterns

Vulnerable versus stable plaque, coronary artery anatomy

STEMI/NSTEMI/ clinical variants in ECG

12 versus 3 lead ECG (Whats the difference?)

Let go current (What is this, why does it occur)

Effect of electrical frequency on shock

Skin effect

Effect of chronaxie (Very short pulses and depolarization)

How electrosurgery works

Potentiomeer versus filters for DC offset correction

Breakdown of ECG circuitwhat each component does

Electrode typesPolarizable

Non-polarizable

Ion flow / electrolysis

Input impedance of different op-amp circuits

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You should also know:How to prove all op amp circuits from class with Kirchhoff's laws

How to identify various op amp circuits (inverting, follower/voltage buffer, non-

inverting, summing, etc and immediately know the associated gain formulas

and then be able to go and apply the necessary Kirchhoff's laws for the proof

What a potentiometer is and how it can be used for offset correction

The total and complete proof of the instrumentation amplifier using kirchhoff's

laws

Filters and calculating filter impedancePolarizable versus non-polarizable electrodes why to use one versus the other

and what they are

Calculating the cardiac vector (Practice this!)

Effect of frequency on electrical shock and heart disruption

What each part of the ECG circuit does and why it is there

The golden rules of the Op-amp

Heart/muscle physiology and action potentials

The Nernst potential and how it applies to this course

Capacitative coupling and ground loops (electrical safety)

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