Electronic Principles And Devices I Introduction

Tishk International University Engineering Faculty Mechatronics Engineering Department Lecture 1: 5/10/2022 Electronic Principles and Devices I Introduction Instructor: Dr. Rand Basil Alhashimie

Electronic Principles and Devices I Theoretical Part: 2 hours per week. 2 Quizzes and 2 Homework. Attendance is required Practical Part: 2 hours per week. Submit the laboratory report, one per each lab (10 reports) Attendance is required

Student Responsibilities English Language. Each student requires to have a scientific calculator. The student requires to bring a hardcopy of the lecture or notebook. Submit the lab-report and the homework on-time The attendance and completion of all exams and assignments.

Electronic Principles and Devices I Syllabus The introduction of Semiconductor devices Diode Physical Operation of the diode Diode application (Rectifier) Zener Diode Transistor BJT Transistor Common Base Common Emitter Common Collector

Reference Thomas L. Floyed, 2012, Electronic Devices: Electron Flow Version, 9th Edition. https://hristotrifonov.files.wordpress.com f

Total Mark 100% Quiz 10% Homework 5% Laboratory 10% Midterm Exam 25% Practical exam 10% Final Exam 40%

Outline 1. 2. 3. 4. 5. 6. 7. 8. 9. Introduction of Semiconductor Silicon Diode Diode Forward bias Diode Reverse bias Voltage-Current Characteristics of a Diode Practical Diode Model Next lecture Reference 7

Semiconductor Solid materials can be categories under three main types: Conductor: when the object made of a metal allows the flow of the electrical current through the object, such as gold, silver, copper, etc. Insulator: when the object made of material that does not easily transmit electrical current, such as rubber, glass, etc. Semiconductor: when the object made of a material that has a conductivity value lower than the conductor and higher that the insulator. 8

Semiconductor

Semiconductor Semiconductor: when the object made of a material that has a conductivity value lower than the conductor and higher that the insulator. Semiconductor can be called as a part time conductor, because its conductivity can be controlled. Fig. 1: Conductivity of Materials 10

Semiconductor Silicon is a chemical material with symbol Si, and it is the common materials used to build the semiconductor devices. Silicon is the main ingredient of sand. Around Fig.2: Silicon Powder 25% of the earth crest is silicon. The Silicon is grown in a crystal structure, and it cuts into wafers to make electronic devices. Fig.3: Pure Silicon from Sand 11

Silicon Two types of silicon available: N-type and P-type. When the phosphorus is added to the Si, the resulting called N-Type Silicon (N means the Fig. 4: N-Type Silicon negative charge of silicon). When the boron is added to the Si, the resulting called P-Type Silicon (P means the positive charge of silicon). Fig. 5: P-Type Silicon 12

Diode A diode is a small piece of semiconductor materials, usually silicon. It is formed by combine N-type and P-type silicon. Fig. 6: PN Diode The p-region called anode and the n-region called cathode, and the region between them called pn junction. Fig. 7: Diode Symbol 13

Diode

Diode To bias the diode, it requires to apply dc voltage across it. The current flow in one direction only, from the anode to the cathode. Diode has two biases, forward and reverse. Fig.8: Diode connects to voltage supply (Vbias) 15

Diode Forward Bias Forward bias, it allows the current to flow through pn junction. Two conditions to make the diode work in a forward bias: 1. When the VBias (Voltage supply) higher than the barrier potential, which is 0.7V. 2. When the positive side of the voltage supply connect to the pregion and the negative supply connect to the n-region. 16

Diode Forward Bias The electrical field supplied by the voltage supply will forced the electrons from the n-region and the holes from p-region, toward the center (pn junction). The combination of the electrons and Fig. 9: Electrons and holes at forward bias the holes make the current passing through the diode. 17

Diode Reverse Bias Reverse bias is the condition that prevents the current to flow through the diode. It happens when connect the voltage supply in a reverse bias, as shown in Figure (12). The p-region to the negative bias of the supply and the n-region to the positive bias of the supply. The reverse bias happens because the positive side of the voltage supply pulls the electrons, which are the majority at n-region, from the pn junction. 18

Diode Reverse Bias The electrons flow toward the positive side of the voltage supply, in order to that positive ions are created, as shown in Figure (10). However, in the p-region, electrons from the negative side of the voltage supply enter and move from hole to hole toward the center region, where they create additional negative ions. The flow of the electrons can be viewed as the holes pulled toward the positive side, as shown in Figure (10). 19

Diode Reverse bias The result of both movement at n-region and p-region is widening the center region (Depletion region). Fig. 10: Electrons and holes at reverse bias 20

Diode Bias Fig. 11: No bias Fig. 12: Forward bias Fig.13: Diode on reverse bias 21

Voltage-Current Characteristics of a Diode When the forward-bias applied across the diode, there is current called forward current (IF). The resistor is used to limit the forward current to a value that will not overheat the diode and cause damage. Fig. 14: Diode connected with a dc voltage supply 22

Voltage-Current Characteristics of a Diode As you continue to increase the forward-bias voltage (VBias), the current continues to increase very rapidly, but the voltage across the diode increases only gradually above 0.7 V. This small increase in the diode voltage above the barrier potential is due to the voltage drop across the internal dynamic resistance of the semiconductive material. A typical curve for the V-I characteristic curve for a forward-biased diode is shown in Figure (15). 23

Voltage-Current Characteristics of a Diode The diode forward voltage (VF) increases to the right along the horizontal axis, and the forward current (IF) increases upward along the vertical axis. As shown in Figure (15), the forward current increases very little until the forward voltage across the pn junction reaches approximately 0.7 V at the knee of the curve. After this point, the forward voltage remains nearly constant at approximately 0.7 V, but IF increases rapidly. There is a slight increase in VF above 0.7 V as the current increases due mainly to the voltage drop across the dynamic resistance. The IF scale is typically in mA. 24

Voltage-Current Characteristics of a Diode Fig. 14: Diode with a variable dc voltage supply Fig. 15: V and I at the forward bias 25

Voltage-Current Characteristics of a Diode When a reverse-bias voltage is applied across a diode, there is only an extremely small reverse current IR through the pn junction. With 0 V across the diode, there is no reverse current. As you gradually increase the reverse-bias voltage, there is a very small reverse current and the voltage across the diode increases. When the applied bias voltage is increased to a value where the reverse voltage across the diode VR reaches the breakdown value (VBR), the reverse current begins to increase rapidly. 26

Voltage-Current Characteristics of a Diode A typical curve for the V-I characteristic curve for a reverse-biased diode is shown in Figure (17). The diode reverse voltage (VR) increases to the left along the horizontal axis, and the reverse current (IR) increases downward along the vertical axis. There is very little reverse current (usually µA or nA ) until the reverse voltage across the diode reaches approximately the breakdown value (VBR) at the knee of the curve. After this point, the reverse voltage remains at approximately VBR, but IR increases very rapidly, resulting in overheating and possible damage if current is not limited to a safe level. 27

Voltage-Current Characteristics of a Diode Fig. 16: Diode with a variable dc voltage supply at Reverse bias Fig. 17: V and I at the reverse bias 28

Practical Diode Model When the diode is forward-biased, it is equivalent to a closed switch in series with a small equivalent voltage source (VF). The VF equal to the barrier potential (0.7 V) with the positive side Fig. 18: Practical diode model at forward bias toward the anode, as shown in Figure (18). 29

Practical Diode Model VF 0.7V Based on the Kirchoff's voltage law: VBias - VF – V*RLimit 0 V*RLimit IF * RLimit Then IF (VBias – VF)/ RLimit 30

Practical Diode Model When the diode is reverse-biased, it is equivalent to an open switch just as in the ideal model, as shown in Figure (19). The barrier potential does not affect reverse bias, so it is not a factor. Fig. 19: Practical diode model at forward bias VF 0V, IR 0A then VR VBias 31

Next Lecture Half Wave Rectifier. 32

Reference Thomas L. Floyed, 2012, Electronic Devices: Electron Flow Version, 9th Edition. 33

Diode Reverse Bias Reverse bias is the condition that prevents the current to flow through the diode. It happens when connect the voltage supply in a reverse bias, as shown in Figure (12). The p-region to the negative bias of the supply and the n-region to the positive bias of the supply. The reverse bias happens because the positive side of the voltage