Introduction to electronics(Syllabus)

Course Title: Introduction to Electronics Instructor: Ashraf A. Ali

e-mail: ashraf@hu.edu.jo WEB: staff.hu.edu.jo/ashraf

Office Hours:Sun , Tue, Thu 12:00-1:00

Lecture Time:Tue, Thu 1:00- 2:00 Lecture Hall E2010

Introduction to electronics(Syllabus)

Textbook(s):” Principles and applications of electrical engineering ” 5th ed , Giorgio Rizzoni. McGraw-Hill,2007

Other required material:Lectures

Plan:First Exam(25 Points) Second Exam(25 Points) Final Exam(50 Points)

Introduction to electronics (Syllabus)

Course objectives: The student should be able to:

1. Study the prosperities of Semiconductor materials and PN junctions.

2. Study and analyze Diode properties and operation modes.

3. Study the applications of electronic circuits. 4. Analyze the Zener Diode and schottky diode operation

and applications. 5. Study rectifier, Clipper, and Clamper circuits. 6. Analyze the Bipolar Junction Transistors "BJT". 7. Introducing the operational amplifiers operations and

types.

Introduction to electronics (Syllabus)

Topics covered: 1. Semiconductors, PN junction Diode. (Ch9) 2. Circuit Models of semiconductor diodes.v 3. Rectifier Circuits. (Ch9) 4. Zener diodes and its applications. (Ch9) 5. Bibolar Junction Transistors and its operation. (Ch10) 6. BJT large signal model. (Ch10). 7. Q-point analysis of BJT. (Ch10). 8. Opertionl Amplifiers. (Ch8).

CH9 : Semiconductors and Diodes

Semiconductor Materials and Devices

Intrinsic Semiconductors Ideally 100% pure material

Silicon (Si)• Most common semiconductor used today

Germanium (Ge)• First semiconductor used in p-n diodes

Gallium Arsenide (GaAs)• Compound Semiconductor

Silicon (Si)

Covalent bonding of one Si atom with four other Si atoms to form tetrahedral unit cell.

Valence electrons available at edge of crystal to bond to additional Si atoms.

Effect of Temperature on Silicon

At 0K, no bonds are broken.

Si is an insulator.

As temperature increases, a bond can break, releasing a valence electron and leaving a broken bond (hole).

Current can flow.

Movement of Holes

A valence electron in a nearby bond can move to fill the broken bond, making it appear as if the ‘hole’ shifted locations.

Intrinsic concentration

310105.1)300,( cmxKSini

in Intrinsic Concentration of semiconductor is the number of charges at certain temperature.

Extrinsic Semiconductors (Doping Semiconductors)

Impurity atoms replace some of the atoms in crystal

Group V atoms in Si are called donor impurities.

Column III in Si atoms are called acceptor impurities.

Phosphorous – Donor Impurity in Si

Phosphorous (P) replaces a Si atom and forms four covalent bonds with other Si atoms.

The fifth outer shell electron of P is easily freed to become a conduction band electron, adding to the number of electrons available to conduct current.

Boron – Acceptor Impurity in Si

Boron (B) replaces a Si atom and forms only three covalent bonds with other Si atoms.

The missing covalent bond is a hole, which can begin to move through the crystal when a valence electron from another Si atom is taken to form the fourth B-Si bond.

Electron and Hole Concentrationsn = electron concentrationp = hole concentration

n-type material (with added donors)

n (donor concentration) >> nip (acceptor concentration) << pi

p-type material (with added acceptors)p (acceptor concentration) >> pin (donor concentration) << ni

Recombination Process

In Recombination: electrons merge with holes.

But still free electrons exist due to the continuing kinetic energy inside the covalent bounds of the semiconductor material.

P-N Junction

a section of p-type material and a section of n-type material are brought in contact to form a pn junction (or Diode).

Recombination process occurs at the depletion region Net average charge at depletion becomes zero.

Offset voltage Vγ

The movement of carriers creates a space charge or depletion region with an induced electric field near x = 0.

Offset voltage, Vγ (or Vbi) , is developed across the junction.

Drift and Diffusion current

Drift (Saturation Reverse current Is) flows through the junction from right to left.

Ex: Is(Silicon) = 10-9 A

Diffusion current: flows from the P-type plate to the N-type plate and it is a function of temperature and Diode voltage.

PN junction is refered as “Diode”

Diode Symbol

Id : diode total current from P-type to N-type side

VD diode voltage across the ohmic contact.

VD is not similar to the

offset voltage.

Id is a fuunction of VD

Diffusion Current (Id) Id is characterized by the following equation:

- I0 Is the reverse saturation current (or Is)

- Id : diffusion current.

- ID Is the total diode current.

- q: charge of electron Voltage of the diode- VD Voltage of the diode

- K: Boltzmann's constant- T: room temperature in Kelvin (300 K)

Biasing modes of diodes

Diodes can be either Reverse Biased or forward Biased based on the value of the diode voltage (VD).

The Biasing is done by forcing the change in VD using external source.

Reverse Biasing mode of operation

Happens when the potential is reversed at the ohmic contact.

Recombination occurs at the edges of the plates.

The depletion region becomes wider.

The diffusion current (Id) becomes zero.

Reverse Bias

Increase in space-charge width, W, as VR increases to VR+VR.

Creation of more fixed charges (-Q and +Q) leads to junction capacitance.

Forward Biased p-n Junction

Applied voltage, vD, induces an electric field, EA, in the opposite direction as the original space-charge electric field, resulting in a smaller net electric field and smaller barrier between n and p regions.