Lecture 16: Electrical Engineering II

EEN 112: Introduction to Electrical and Computer Engineering

Professor Eric Rozier, 4/10/13

EXAM GRADES

Quiz III Grades

Midterm Grades

• Midterm I– Average: C+– 25% - B+– 50% - B-– 75% - C-

• Midterm II– Average: B– 25% - A– 50% - B– 75% - C

Midterm II Grades

Midterm I & II Grades

Course Grades

• Average: A-• 25% - A• 50% - A-• 75% - B

Course Grades

The Importance of Trust

• Sarbanes-Oxley Act• HIPAA• California Proposition 11• FISMA• Massachusetts

201 CMR 17.00

Over 10,000 regulations

Users expect data to be stored indefinitely…

Reliability

• What responsibilities do we have as engineers to preserve information?

• Should we be liable if our systems fail in these ways?

• What limits should there be to liability?• Can a system ever be fully reliable?• What responsibility do we have to report the

limits to our systems reliability?

High Frequency Trading

• Algorithmic trading, seeks to exploit small differences in prices, millions of programs running

• How do they interact?• How does something

written by Company Aaffect somethingwritten by Company B?

High Frequency Trading

• 2010 Flash Crash – largest intraday point loss– Losses recovered in minutes, but scared regulatory

bodies• US SEC and CFTC

consluded that HFTcontributed to thevolatility.

High Frequency Trading

• SEC and FTC stated – “market makers and other liquidity providers widened their quote spreads, reduced liquidity, and withdrew from the market”

• Some signal set offtheir algorithms,caused a jointmovement whichhelped cause the crash

High Frequency Trading

• What responsibility do we have to prevent disasters?

• What happens when our duty to our employer might conflict?

• How do we weighour responsibilities?

The broader world is complex

• Critical thinking• Awareness of situations and consequences• Working with regulators, and employers• Maintaining integrity

ELECTRICAL ENGINEERING

Resistors

• What do the bands mean?

Ohm’s Law

• Resistance, Voltage, and Current are related…

• V –• I – • R –

POWER!!!

• P = V I• V = I R, so…

– P = (I R) I = I^2 R• I = V/R, so…

– P = V (V/R) = V^2/R

Diodes

Diodes

LED

• Light Emitting Diode– Diode that emits light

(fancy that!)– Low power, bright– Come in various colors

• Using LEDs– Use in correct

orientation– Use a current limiting

resistor!!!

LED History

• Invented in 1962 by Dr. Nick Holonyak while at General Electric

• Dr. Craford (Dr. Holonyak’s student) invented the first colored LED

• First LEDs produced by Monsanto Company in 1968

LEDs

LEDs

LEDs

Semiconductors

• Electrical conductivity between a conductor and an insulator

• Conductivity increases with temperature

• P-type semiconductor– Excess holes

• N-type semiconductor– Excess free electrons

• “Doping” sets these properties

Doping

• Not just for the Tour de France!

• Introduce impurities– Gallium Arsenic gas very popular

• Grow silicon in an environment with the impurities in certain concentrations

LEDs

P-Type?

HOLES!

N-Type?

FREE ELECTRONS!

P-Type?

HOLES!

N-Type?

FREE ELECTRONS!

LEDs

Semiconductors

• Both P and N junctions are relatively conductive… under the right circumstances

• Junctions get depleted of charge

LEDs

LEDs

• Often used as indicator lights• More recently for

– TVs– Flash lights– Light bulbs– Jumbo-tron displays