Diode Modelling PDF

# P-N Junction ## Energy Levels of Semi-Conductors The energy levels of semi-conductors can be modified so that Si or Ge, which are normally insulators, will conduct electricity. ## Doping Doping is a process where impurities are added to the semi-conductor to lower its resistivity. We add atom...

# P-N Junction ## Energy Levels of Semi-Conductors The energy levels of semi-conductors can be modified so that Si or Ge, which are normally insulators, will conduct electricity. ## Doping Doping is a process where impurities are added to the semi-conductor to lower its resistivity. We add atoms that have different numbers of valence shell electrons 3 or 5 to a piece of silicon. - Phosphorous, Arsenic, Antimony - 5 electrons - Aluminium, Boron - 3 electrons ### Normal Silicon * Image: A diagram showing the silicon atom with 4 electrons. ### P-type * Image: A diagram showing the silicon atom with 3 electrons and a hole. * The hole is labeled as an *Acceptor*. ### N-type * Image: A diagram showing the silicon atom with 5 electrons and a hole. * The extra electron is labeled as a *Donner*. ## P-type and N-type * Image: A diagram showing a P-type and an N-type semiconductor side by side. * The P-type has acceptors that have a positive charge. * The P-type silicon also has positive holes. * The N-type has donors that have a negative charge. * The N-type silicon also has electrons. ### Summary of P-type and N-type * **P-type:** Majority current carriers are **holes**. Minority current carriers are **electrons**. * **N-type:** Majority current carriers are **electrons**. Minority current carriers are **holes**. ## Diode * Image: A diagram showing a Diode with Anode and Cathode labeled. ## Diode Operation and Characteristics ### Forward Biased * Image: A circuit diagram of a Forward Biased diode. * **VA >= VC** * Diode is **on** (switch) * IF is **large** * Image: Another diagram showing a Forward Biased diode with electrons moving toward the positive side, and holes moving toward the negative side. ### Reverse Biased * Image: A circuit diagram of a Reverse Biased diode. * **VA < VC** * Diode is **off** (switch) * IR is **small** * Image: Another diagram showing a Reverse Biased diode with electrons moving toward the positive side, and holes moving toward the negative side. ### **R** is important in Forward Bias **R** limits the current, IF. ## Diode Modeling ### Complete model * Image: A circuit diagram with a diode modeled as a resistor, a voltage source, and a forward resistor. * **VB = 0.7 Si** * **VB = - 0.3 Ge** * **IF = (VS-.07) / (R+Rd)** * **VD = VB + IF Rd** * **Rd = Very Small** * **IF = Very Large** * **RR = Very Large** * **IR = (VS - VD) / (R+RR)** * **VD = Very Large** * Image: A diode characteristic curve showing forward and reverse regions. ### Practical Model * Image: A circuit diagram with a diode modeled as a resistor and a voltage source. * **If = (VS - 0.7) / R** * **VB = VD = 0.7 Si** * **VB = VD = -0.3 Ge** * **IR = Zero** * **VD = VS** * Image: A diode characteristic curve showing forward and reverse regions. ### Ideal Model * Image: A circuit diagram with a diode modeled as a perfect switch. * **VD = 0** * **IF = VS / R** * **IR = 0** * **VD = VS** * Image: A diode characteristic curve showing forward and reverse regions. ## Applications of Diodes 1. Protection Circuits 2. Convert AC -> DC 3. Voltage Regulator 4. Voltage Multiplier 5. Non-linear Mixing of Two Voltages ## Types of Diodes 1. General Purpose Diode 2. Zener Diode 3. Photodiode 4. LED 5. Schottky Diode ## Rectifier Circuits ### Half Wave Rectifier * Image: A circuit diagram showing a Half-Wave Rectifier. * Image: A sine wave input and a corresponding output waveform. * **Vin = Vinm Sin (wt)** ### +ve half cycle * Image: A Circuit Diagram showing a Half-Wave Rectifier with Positive Input Voltege. * **D** is forward biased * **Vo ≈ 0** * **Vo = 0** (Ideal Diode) * **Vo = Vin** (Practical Diode) ### -ve half cycle * Image: A Circuit Diagram showing a Hall-Wave Rectifier with Negative Input Voltage. * **D** is reverse biased. * **Vo = 0** #### Calculation of V om, Vo avg, Vo rms * **Vo max = Vin max** * **Vo max = Vin max - 0.7** (Practical Diode) * **Vo = Vo m Sin (wt)** * **Vo avg = (1 / 2 pi) ∫π (Vo m Sin (wt)) dt = Vo m / π** * **Vo rms = √(1 / 2pi) ∫π (Vo m Sin (wt))² dt = √(Vo m² / 2)** ### Smoothing by a Capacitor * Image: A circuit diagram showing a Half-Wave Rectifier with a capacitor. * Image: A sine wave input waveform, output waveform, and voltage across capacitor. * **VCpp = (Vp / (R L *f * C)) = (Ip / (f * C))** * **Vo avg = Vodc = Vp - (1 / 2)VCpp** ## Full Wave Rectifier ### Using Center Tapped Transformer * Image: A circuit diagram showing a Full-Wave Rectifier with a Center Tapped Transformer. * Image: A sine wave input waveform and a corresponding output waveform. #### +ve half cycle * Image: A circuit Diagram showing a Full-Wave Rectifier with a Center Tapped Transformer and Positive Voltage. * **D1** is forward biased * **D2** is reversed biased * The positive side of the transformer is connected to **D1**. * **D2** is reverse biased. * The output terminal is connected to the positive end of the transformer, and output voltage is positive. #### -ve half cycle * Image: A circuit diagram showing a full-wave rectifier with a center tapped transformer and negative voltage. * **D1** is reverse biased * **D2** is forward biased * The positive side of the transformer is connected to **D1**. * **D1** is reverse biased. * **D2** is forward biased, and output voltage is positive. ### Calculation of V om, Vo avg. Vo rms * **Vo m = Vin m ** * **Vo m = Vin m - 0.7** (Practical Diode) * **Vo avg = (1 / 2pi) ∫π (Vo m Sin (wt)) dt = (Vo m / π)** * **Vo rms = √(1 / 2pi) ∫π (Vo m Sin (wt))² dt = √(Vo m² / 2)** ### Using a Bridge Rectifier * Image: A circuit diagram showing a Full-Wave Rectifier using a Bridge Rectifier. #### +ve half cycle * Image: A circuit diagram showing a full-wave bridge rectifier with positive voltage input. * **D1** and **D4** are forward biased * **D2** and **D3** are reversed biased * The output voltage is positive #### -ve half cycle * Image: A circuit diagram showing a full-wave bridge rectifier with negative voltage input. * **D2** and **D3** are forward biased * **D1** and **D4** are reversed biased * The output voltage is still positive. ### Calculation of V om, Vo avg. Vo rms * **Vo m = Vin m** * **Vo m = Vin m - 1.4** (Practical Diode) * **Vo avg = (1 / 2pi) ∫π (Vo m Sin (wt)) dt = (Vo m / π)** * **Vo rms = √(1 / 2pi) ∫π (Vo m Sin (wt))² dt = √(Vo m² / 2)** ## Peak Inverse Voltage (PIV) ### Half Wave Rectifier * Image: A circuit diagram showing a half-wave rectifier. * **PIV = Vin m** ### Center-Tapped Transformer * Image: A circuit diagram showing a full-wave rectifier with a center-tapped transformer. * **PIV = 2Vin m - 0.7** (Practical Diode) * **PIV = 2Vin m** (Ideal Diode) ### Bridge Rectifier * Image: A circuit diagram showing a full-wave bridge rectifier. * **PIV = Vin m + 0.7** (Practical Diode) * **PIV = Vin m** (Ideal Diode) * **PIV = Vin m - 0.7** (Another Practical Diode) * **PIV = Vin m** (Ideal Diode) ## Frequency Considerations ### Full Wave Rectifier * **T out = 1/2 T in** * **f out = 2 * f in** ### Half Wave Rectifier * **T out = T in** * **f out = f in** ### Ripple Voltage for a Full-Wave Rectifier * **Vripple = Vp - (Ip/2fC)** ## Choose the Correct Answers The document contains a set of multiple-choice questions. It appears that some questions are missing from the document. The following correct answers can be determined from the document: 1. **Increased** 2. **Not Changed** 3. **Increased** 4. **Not Changed** 5. **Forward Biased** 6. **63.7 V** 7. **60 Hz** 8. **120 Hz** 9. **47.8 V** 10. **All of the above.** 11. **Increased** 12. **0.005** 13. **6x10^-3 A** 14. **5 V** # Conclusion The document offers an explanation of the P-N Junction, Doping, and Diodes, including their characteristics, modeling, and applications. Rectifier circuits for both half-wave and full-wave rectification are explained in detail with their respective advantages and disadvantages outlined. It also provides calculations for finding important parameters like peak inverse voltage and ripple voltage for different types of rectifiers. Finally, it includes a set of multiple-choice questions assessing the understanding of diode characteristics.