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Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader

Lecture 6. Diode applications. Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader. Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader. By: Dr Tarek Abdolkader. OUTLINE. Diode circuit analysis Rectifiers Clipping circuits

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Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader

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  1. Lecture 6 Diode applications Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader By: Dr Tarek Abdolkader

  2. OUTLINE • Diode circuit analysis • Rectifiers • Clipping circuits • Clamping circuits • Zener diode Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Electronic devices (802311) Lecture 6 Dr Tarek Abdolkader

  3. Diode circuit analysis Diode dc circuit analysis: • To analyze a diode dc circuit, you must determine first: Is the diode ON or OFF? • To determine the status of the diode: • Assume that the diode is OFF. • Determine the voltage on the diode in this case (which is equal to thevinin voltage Vth). • If Vth < Vcut, then the diode is really OFF and it is replaced by open circuit. • If Vth ≥ Vcut, then the diode is ON and it is replaced by a battery of Vcut Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader • Vcut is 0.7 V for silicon and 0.3 for Ge. (assuming practical model) Electronic devices (802311) Lecture 6 Dr Tarek Abdolkader

  4. Diode circuit analysis Example For the series diode configuration shown, determine VD, VR, and ID. Solution See Example 2.6 page 60 in Boylestad Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Electronic devices (802311) Lecture 6 Dr Tarek Abdolkader

  5. Diode circuit analysis Example For the series diode configuration shown, determine VD, VR, and ID. Solution See Example 2.8 page 61 in Boylestad Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Electronic devices (802311) Lecture 6 Dr Tarek Abdolkader

  6. Diode circuit analysis Example For the series circuit shown, determine Voand ID. Solution See Example 2.9 page 62 in Boylestad Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Electronic devices (802311) Lecture 6 Dr Tarek Abdolkader

  7. Diode circuit analysis Example For the circuit shown, determine ID , VD2 and Vo. Solution See Example 2.10 page 62 in Boylestad Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Electronic devices (802311) Lecture 6 Dr Tarek Abdolkader

  8. Diode circuit analysis Example For the series diode configuration shown, determine I,V1, V2, Vo. Solution See Example 2.11 page 63 in Boylestad Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Electronic devices (802311) Lecture 6 Dr Tarek Abdolkader

  9. Diode circuit analysis Example For the network shown, determine I. Solution See Example 2.13 page 65 in Boylestad Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Electronic devices (802311) Lecture 6 Dr Tarek Abdolkader

  10. Diode circuit analysis Diode ac circuit analysis: • To analyze a diode ac circuit, you must determine at what value of the input the diode transfers from OFF to ON or vise versa? Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader • To determine the transition value at which the diode switches: • Assume that ID = 0 and VD = 0.7 V for silicon and of 0.3 for Ge. (assuming practical model) • Determine Viin this case. It is the transition value of input (Vit). • Calculate Vo for Vi > Vit, and for Vi > Vit. In one of these cases, the diode will be ON and in the other it will be OFF. Electronic devices (802311) Lecture 6 Dr Tarek Abdolkader

  11. Rectifiers Half-wave rectifier: It transforms sinusoidal input to half-wave rectified signal Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Electronic devices (802311) Lecture 6 Dr Tarek Abdolkader

  12. Half-wave rectifier Example Sketch the output voassuming ideal diode. Repeat part (a) assuming practical diode model. Repeat parts (a) and (b) if Vm is increased to 200 V and compare solutions Solution Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader See Example 2.18 page 71 in Boylestad Electronic devices (802311) Lecture 6 Dr Tarek Abdolkader

  13. Rectifiers Full-wave rectifier: • It transforms sinusoidal input to full-wave rectified signal • There are two types of full-wave rectifiers: • Using center-taped transformer. • Using bridge network. Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Electronic devices (802311) Lecture 6 Dr Tarek Abdolkader

  14. Rectifiers center-taped transformer full-wave rectifier : Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Electronic devices (802311) Lecture 6 Dr Tarek Abdolkader

  15. Rectifiers Bridge full-wave rectifier: Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Electronic devices (802311) Lecture 6 Dr Tarek Abdolkader

  16. Rectifiers Peak Inverse Voltage(PIV): • The peak inverse voltage (PIV) is the maximum negative bias applied on the diode. If the diode is biased in the reverse mode with a voltage more than PIV, it will go into breakdown Half-wave rectifier: Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader center-taped transformer full-wave rectifier : Bridge full-wave rectifier: Electronic devices (802311) Lecture 6 Dr Tarek Abdolkader

  17. Rectifiers Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Electronic devices (802311) Lecture 6 Dr Tarek Abdolkader

  18. Power supply unit • To reach the required dc voltage, a filter and regulator should be added to a rectifier circuit. The overall system is called power supply unit (PSU). Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Electronic devices (802311) Lecture 6 Dr Tarek Abdolkader

  19. Power supply unit • While the input is increasing, the diode D is ON and the capacitor is charging with a small time constant. • After reaching the peak, the voltage at the anode will be less than the cathode and D will be OFF. The capacitor will discharge through the load with a large time constant. • When the input exceeds the capacitor voltage, D is again ON. Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Electronic devices (802311) Lecture 6 Dr Tarek Abdolkader

  20. Power supply unit Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Full-wave rectifier is much better than Half-wave rectifier because it gives less ripple. Electronic devices (802311) Lecture 6 Dr Tarek Abdolkader

  21. Clippers • Diode networks that have the ability to “clip” off a portion of the input signal without distorting the remaining part of the alternating waveform are called clippers. • The half-wave rectifier is an example of the simplest form of diode clipper—one resistor and diode. • There are two general categories of clippers: • series clipper: where the diode is in series with the load, • parallel clipper: the diode is in parallel to the load. Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Series clipper Parallel clipper Electronic devices (802311) Lecture 6 Dr Tarek Abdolkader

  22. Clippers • To determine the output voltage: • Assume that ID = 0 and VD = 0.7 V for silicon and of 0.3 for Ge. (assuming practical model) • Determine Viin this case. It is the transition value of input (Vit). • Calculate Vo for Vi > Vit, and for Vi > Vit. In one of these cases, the diode will be ON and in the other it will be OFF. • Sketch Vi and Vo. Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Electronic devices (802311) Lecture 6 Dr Tarek Abdolkader

  23. Clippers Example Determine the output waveform of the network shown assuming ideal diode model. Solution See Example 2.20 page 78 in Boylestad Vit = ‒ 5 V Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader For vi > ‒ 5 V, D is ON  vo = vi+ 5 For vi < ‒ 5 V, D is OFF  vo = 0 Electronic devices (802311) Lecture 6 Dr Tarek Abdolkader

  24. Clippers Example Repeat the previous example if the input waveform is the square wave shown. Solution See Example 2.21 page 79 in Boylestad Vit = ‒ 5 V Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader For vi > ‒ 5 V, D is ON  vo = vi+ 5 For vi < ‒ 5 V, D is OFF  vo = 0 Electronic devices (802311) Lecture 6 Dr Tarek Abdolkader

  25. Clippers Example Determine the output waveform of the network shown assuming ideal diode model. Solution See Example 2.22 page 80 in Boylestad Vit = 4 V Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader For vi > 4 V, D is OFF  vo = vi For vi < 4 V, D is ON  vo = 4 V Electronic devices (802311) Lecture 6 Dr Tarek Abdolkader

  26. Clippers Example Repeat the previous example assuming silicon diode practical model. Solution See Example 2.23 page 81 in Boylestad Vit = 4 ‒ 0.7 = 3.3 V Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader For vi > 3.3 V, D is OFF  vo = vi For vi < 3.3 V, D is ON  vo = 3.3 V Electronic devices (802311) Lecture 6 Dr Tarek Abdolkader

  27. Clamping circuits • The clamping network is one that will “clamp” a signal to a different dc level. • The network must have a capacitor, a diode, and a resistive element, but it can also employ an independent dc supply to introduce an additional shift. • The total swing of the output is equal to the total swing of the input signal. Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader clampers Electronic devices (802311) Lecture 6 Dr Tarek Abdolkader

  28. Clamping circuits Assumptions: • The time constant with the diode is OFF is very large (  ). • The time constant with the diode is ON is very small ( 0 ). Procedure: Start by considering that part of the input signal that will make the diode ON. In the ON state, assume that the capacitor will charge up instantaneously (   0). Find the voltage on the capacitor after charging (with the proper polarity) and the output voltage in the ON state. Move to the OFF state and assume that the capacitor will hold on to its established voltage level in the ON state(   ). Find the output voltage in the OFF state. Keep in mind the general rule that the total swing of the total output must match the swing of the input signal. Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Electronic devices (802311) Lecture 6 Dr Tarek Abdolkader

  29. Clamping circuits Example Find the output voltage of the shown circuit. Solution For vi > 0, D is ON Vit = 0 V For vi < 0, D is OFF Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader D is ON D is OFF Electronic devices (802311) Lecture 6 Dr Tarek Abdolkader

  30. Clamping circuits Example Determine vo for the network shown. Solution See Example 2.24 page 84 in Boylestad For vi < 5, D is ON Vit = 5 V Note that: T = 1/f = 1 ms (OFF) = RC = 100 ms (ON) ~ rDC ~ few seconds For vi > 5, D is OFF Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader D is ON D is OFF Electronic devices (802311) Lecture 6 Dr Tarek Abdolkader

  31. Clamping circuits Example Repeat the previous example assuming Si diode. Solution See Example 2.25 page 85 in Boylestad For vi< 4.3 V, D is ON Vit = 4.3 V Note that: T = 1/f = 1 ms (OFF) = RC = 100 ms (ON) ~ rDC ~ few seconds For vi> 4.3 V, D is OFF Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader D is ON D is OFF Electronic devices (802311) Lecture 6 Dr Tarek Abdolkader

  32. Clamping circuits Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Electronic devices (802311) Lecture 6 Dr Tarek Abdolkader

  33. Clamping circuits Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Electronic devices (802311) Lecture 6 Dr Tarek Abdolkader

  34. Zener diode I When a sufficiently large reverse voltage is applied to a p-n junction, the junction breaks down and conducts a very large current. The reverse voltage at which the current increases sharply is called the BREAKDOWN VOLTAGE, or the zener voltage Vz Vz V -Io I ~- Io Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Electronic devices (802311) Lecture 6 Dr Tarek Abdolkader

  35. Zener diode Procedure for dc inputs: Determine the state of the Zener diode by removing it from the network. Substitute the appropriate equivalent circuit and solve for the desired unknowns. Procedure for ac inputs: Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader • Determine the transition input at which the Zener diode will switch its state by assuming that ID = 0 and VD = ‒Vz. • Determine Viin this case. It is the transition value of input (Vit). • Calculate Vo for Vi > Vit, and for Vi > Vit. In one of these cases, the zener diode will be ON and in the other it will be OFF. • Sketch Vi and Vo. Electronic devices (802311) Lecture 6 Dr Tarek Abdolkader

  36. Zener diode Example (a) For the Zener diode network shown, determine VL, VR, Iz, and Pz. (b) Repeat part (a) with RL= 3 kΩ. Solution See Example 2.26 page 88 in Boylestad Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader D is OFF Electronic devices (802311) Lecture 6 Dr Tarek Abdolkader

  37. Zener diode Example (a) For the Zener diode network shown, determine VL, VR, Iz, and Pz. (b) Repeat part (a) with RL= 3 kΩ. Solution See Example 2.26 page 88 in Boylestad Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader D is ON Electronic devices (802311) Lecture 6 Dr Tarek Abdolkader

  38. Zener diode Example (a) For the network shown, determine the range of RLand ILthat will result in VLbeing maintained at 10 V. (b) Determine the maximum wattage rating of the diode. Solution See Example 2.27 page 91 in Boylestad Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader D must be ON: Electronic devices (802311) Lecture 6 Dr Tarek Abdolkader

  39. Zener diode Example Determine the range of values of Vi that will maintain the load voltage in the Zener diode circuit shown at 20 V. Solution See Example 2.28 page 92 in Boylestad Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader D must be ON Electronic devices (802311) Lecture 6 Dr Tarek Abdolkader

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