ECE 1004 Exam 2

Mesh Analysis Procedure

• Identify individual meshes and assign mesh current

• Identify super-meshes if a shared current source exists

• Develop mesh equations using KVL and Ohm’s Law

• Solve the simultaneous equations to find mesh currents, which then allow for the calculation of any voltage or power in the circuit.

• REMEMBER SOURCE EQ IF SUPER MESH

Linear two-terminal circuit

• Electrical network accessible via two external connection points (terminals)

• Passive linear comps: resistors, inductors, capacitors

• Independent voltage/current sources, and linearly dependent sources (ex VS)

• Connects to external circuits or loads through exactly two external nodes (often A & B)

Thevenin’s Theorem

• Any linear two circuit containing multi sources and resistors can be replaced by a much simpler equivalent circuit made of: One voltage source VTh in series w/ one resistance RTh

Complex circuit supples power to load resistor → So we reduce the source network to VTh in series w/RTh

Thevenin → How To

• Remove the load

• Find the open-circuit voltage

• Find RTh (Deactivate → Replace ideal voltage source w/short circuit, and ideal current source w/voltage circuit

Norton’s Theorem

• Any linear two-terminal can be replaced by an equivalent circuit consisting of: One current source IN and one resistor RN connected in parallel w/ the current source.

Norton’s Theorem → How To

• Remove the load (same as T)

• Short the output and find the Norton current (IN = ISC)

• Find the Norton Resistance (Same as T: voltage - open, current - open)

then solve for load, draw, etc

Source transformation

• Replaces a voltage source within an equivalent current source (or vice versa) without changing the behavior seen from the external terminals

(Ex voltage source in series w resistor → current source in parallel w resistor)

RESISTOR DOESN’T CHANGE : I = Vs/R

CURRENT ARROW(direction) TO POS. TERMINAL OF VOLT

Capacitor

• A passive electrical component that stores electrical energy in the form of an electric field

• Consists of two conductive plates W/ an insulating material (dielectric) between them

COMPONENT THAT TEMPORARILY STORES ELECTRICAL ENERGY AND RELEASES IT WHEN NEEDED

How does a Capacitor work?

Voltage source is connected across capacitor and electrons push from one plate to another

THUS, one plate is negatively charged and other equally positive

Middle is insulating so electrons can’t pass through

SO, electric field forms between the plates and ENERGY is stored in field

HAPPENS until capacitor voltage equals source voltage, then charging stops and current = 0 and capacitor is OPEN circuit

Voltage creates a electric field

Capacitor Applications

• Blocking DC curent

• Blocking AC current

• Shift phase

• Store energy

• Suppress noise

• Start motors

• Provide pulse power

Capacitor Properties

• w/DC applied voltage is constant and Current = 0 (i = Cdv/dt, and dv/dt = 0)

• Voltage across a capacitor must change smoothly over time (no infinite current or abrupt change)

Decoupling/Bypass Capacitors

• Very important for situations where you want to reduce noise on the power rails, basically filter signal (As you know!)

Inductor

• A passive electrical component that stores electrical energy in the form of magnetic field when current passes through it

• Consists of a core material wrapped w/ winding insulating copper wire and a magnetic forms around it

How do Inductors work

• When current passes through the coil, a magnetic field is created around it

• Stronger current, stronger magnetic field and more energy is stored

• Current creates a magnetic field

Inductor Properties

BASICALLY OPPOSITE TO CAPACITOR!

• w/DC applied current is constant and voltage = 0 (i = Cdv/dt, and dv/dt = 0) (SO SHORT)

• current across a capacitor must change smoothly over time (no infinite voltage or abrupt change)

Capacitor vs Inductor

Capacitors are..:

• charge up fast (peak current is at 0 initial voltage)

• discharge quickly too, current changes direction quickly

Inductors are..:

• opposing emf resist changes

• so inductors charge slowly and discharge slowly

• inductor current will not change direction abruptly

Semiconductor

• Material who’s electrical conductivity lies between that of a conductor and insulator

Conductor - allows current to flow easily

Semiconductor - conducts current under some conditions and resists current under other conditions

Insulator - resists current

Why silicon

abundant, stable, and suitable (14 electrons total 4 in valence and held by covalent bonds)

Intrinsic semiconductor

• Completely pure semiconductor, no doping (mixing)

• Electrical conductivity is determined by the thermal energy of material rather than chemical impurities

Electron-hole

• At low-temps, electrons in covalent bonds

• At room-temps, thermal energy can break some bonds, the breaking allows electrons to move leaving behind holes and if enough energy can create electron-hole pair

Doping

• Since pure silicon is not conductive enough on its own, a very small amount of another element is added to improve its electrical behavior

N-type semiconductor

• N-type silicon is made by adding an impurity w/five valence electrons, such as phosphorus

• One leftover electron, so it can move easily and carry current

• Electrons majority carriers, holes minority carriers

N COMES FROM ELECTRON MAJORITY NEGATIVE

P-type semiconductor

• P-type silicon is made by adding an impurity w/three valence electrons, such as boron

• Four electrons needed to create four bonds, only 3, so one incomplete bond aka HOLE

• Holes are majority carriers, electrons are the minority carriers

P COMES FROM POSITIVE BEHAVIOR OF HOLES

PN-junction and HOW

• When P-type and N-type materials are joined they form a PN-junction, which is basic structure of diode

how it works

• Electrons diffuse from the N-side toward to P-side

• Holes diffuse from P-side toward the N-side

• Electrons and hole combine near the junction, creating a region nearby that’s depleted of mobile charge carriers called DEPLETION REGION

• fixed ions create internal electric field which forms a potential barrier that opposes further diffusion

Forward/reverse biasing

Vd = 0.7 V (of silicon pn-junction)

• forward: when voltage > 0.7, diode conducts current since voltage opposes the built-in-field

• reverse: increases effect of built-in-field, eliminating possibility of current flow

Semiconductors:

1. Diode

2. LED (Light-emitting diode)

3. Photodiode

4. Solar celL

5. Transistor

6. Integrated circuit

Solar panel

• sillicon is used, photons of light create electron-hole pairs

• E field sweeps electrons out, creating photocurrent

• Current sourcing is dependent on the amount of sunlight

Biasing LEDs/Transistor

Biasing LED: must contain resistor, limited current

Transistor: made up of two diodes

Evolution of Computing Technology

1. Abacus

2. Mechanical Calculator

3. Vacuum tubes

4. Transistors

5. Integrated circuits

6. Microprocessors

7. Personal computers

8. Internet

9. Smartphones

10. Artificial Intelligence

Recent Developments in Technology

1. Artificial Intelligence

2. Machine Learning

3. Internet of Things

4. Cloud Computing

5. Edge Computing

6. Robotics

7. Self-Driving Cars

8. Smart Homes

9. Wearable Devices

10. 5G/6G Technology

11. Quantum Computing

AI/ML

-Learning

• Reasoning

• Problem solving

• Understanding language

• Recognizing images

• Making decisions

ML IS SUBSET OF AI, MORE FOCUSED ON LEARNING OBVI

Internet of Things

• A network of physical devices connected to the internet

• These devices collect data, share information, and communicate automatically

• EX: smart thermostat/refrigerator/watch/traffic lights/watch

Cloud Computing

• Cloud computing allows users to store data and run applications over the Internet

instead of on their own computers.

• Access anywhere, Automatic backup, Easy sharing, Large storage

• EX: Google Drive, Microsoft OneDrive, Dropbox, Netflix, Gmail

Robotics

• Robotics combines Electronics, Sensors, Mechanical engineering, Artificial Intelligence to build intelligent machines.

• EX: Manufacturing/Medicine

Data

• Data is a collection of raw facts, figures, symbols, measurements, or observations that can be processed by a computer to produce meaningful information.

• Data → Processing → Information

• Computer stores in binary digits or bits

Decimal conversion to new bases (to convert fractional part of decimal)

1. Multiply the fraction by the target base

2. Record the integer part of the result

3. Keep only the fractional part

4. Repeat until: The fractional part becomes zero, or you obtain the desired number of digits

5. Read the recorded integers from top to bottom

Converting Binary to Octal

• Group bits in groups of 3 (if bits are not a multiple of 3 then add 0’s)

• Convert the three bits to a decimal number

• Number in octal is is combination of these numbers