Electronics: Basic to clinical

Karl E Misulis MD,PhD

Basic Electronics for Neurology

Electricity and basic circuit theory Filters and amplifiers Digital signal analysis Displays Electrodes Artifacts and noise Electrical safety

Why do I need to know this?

Large part of the clinical neurophysiology boards.

Might be nice to understand how your equipment works.

I make money from the sale of the definitive text…Essentials of Clinical Neurophysiology, www.elsevier.com

ABPN: Clinical neurophysiology

Board certified in neurology, child neurology, or psychiatry

Finished 1 year of ACGME-approved training in CN, not during residency. May be part time (at least 1/2 time)

Certification: 5 hours Re-certification: 3 hours

ABPN: Clinical neurophysiology

Core neurophysiology (18%) Basic and applied neurophysiology

EEG (38%) Methods, Basic patterns, variants Clinical correlations

EMG (38%) Methods, Basic patterns Clinical correlations

Sleep (6%)

Should I take the EEG boards?

Basic electronics

Overview of atomic physics Basic electrical devices Circuit theory Electrical equipment Patient - equipment interface

Overview of atomic physics

Atoms Sub-atomic particles

Electrons Protons Neutrons

Orbitals and clouds

Attraction is the key to everything…

Atomic structure

Great myths in America…

Lightening never strikes twice in the same place.

Good things come to those who wait. Cutting taxes reduces the budget deficit. Anything is possible.

Probability …

High probability Low probability Impossible

Conductors

Laws…

Important laws

Do not offer to perform a consult. Do not ask your nurse out on a date. Do not discriminate against potential

employees on the basis of race, color, creed, health condition, or competence.

Important laws

Ohm's law Kirchoff's current law Kirchoff's voltage law

Ohm's law

Kirchoff's laws: A. Current & B. Voltage

Kirchoff's current law

Expressed mathematically:

or, rearranging:

Since currents flowing out of the node are actually negative:

Or, for any node:

I I I

I I I

I I I

Ii

3 1 2

1 2 3

1 2 3

0

0

0

Kirchoff's laws

Kirchoff's voltage law

For any circuit loop, the sum of thevoltage sources is equal to the sum of the

voltage drops.

E xpressed m athem atically:

or, for any loop:

V V V

V

T

i

1 2 0

0

Resistors…

Resistor theory Function of resistors Resistors in series Resistors in parallel

Theory of resistors

Series resistancesFrom Ohm's Law:

and

And from Kirchoff' s voltage law:

and the equivalent resistance of the system is:

then:

Thus, for series resistances:

V I R V I R

V V V

RV

I

RI R I R

IR R

R R

eq

eq

eq i

1 1 2 2

1 2

1 21 2

( ) ( )

Theory of resistors

Parallel resistances

...1111

:resistance of reciprocal theis econductanc Since

resistors. individual theof esconductanc theare

and , , and econductanc total theis Where

...

:allymathematic Expressed

linearly. sum esConductanc

es.conductanc parallel are sresistance Parallel

321

321

321

RRRR

GGGG

GGGG

T

T

T

Capacitors…

Capacitors

Function of capacitors Store energy as a separation of charge Capacitative current

Effect of capacitors on circuits Types of capacitors

Component Contaminant

Capacitors

Inductors

Function of inductor Effect of inductor on current flow Types of inductors

Component Contaminant

Inductors

Semiconductors…

Semiconductors

Construction Function of semiconductors

"semi-conduct" Junction effects

Use in diodes and transistors

Semiconductors

Diodes

Rolling on to the end…

Summary…

Atomic theory governs charge and current properties in biologic and physical circuits.

There are some basic principles which you must know for the ABPN-CN boards. Resistor and capacitor theory Ohm's law & Kirchoff's laws Filter theory

Knowledge of basic electronics is more than just of academic importance.