ee348_Experiment04 - Laboratory Experiment 4 EE348L...

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University of Southern California. EE348L page1 Lab 4 Laboratory Experiment 4 EE348L B.Madhavan Revised by: Aaron Curry
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University of Southern California. EE348L page2 Lab 4 Table of Contents 4 Experiment #4: Diodes ............................................................................................. 5 4.1 Introduction ............................................................................................................................. 5 4.2 Theory ...................................................................................................................................... 5 4.2.1 p-n Junction Basics .................................................................................................... 5 4.2.2 AC signal behavior ..................................................................................................... 8 4.2.3 Junction and Diffusion Capacitance .......................................................................... 9 4.3 Applications in circuits ............................................................................................................ 9 4.3.1 Large Signal Diode Model ........................................................................................ 9 4.4 Diode simulation in HSpice ................................................................................................... 11 4.5 Transfer characteristic modeling using ideal diodes ............................................................. 14 4.6 Conclusion ............................................................................................................................. 16 4.7 Revision History .................................................................................................................... 16 4.8 Reference Reading ................................................................................................................. 16 4.9 Pre-lab Exercises .................................................................................................................. 17 4.10 Lab Exercises ........................................................................................................................ 20
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University of Southern California. EE348L page3 Lab 4 Table of Figures Figure 4-1: Equilibrium charge profile for p-n junction. ..................................................................... 4 Figure 4-2: Equilibrium energy band profile for p-n junction ............................................................. 6 Figure 4-3: Energy profile for large reverse bias ............................................................................... 6 Figure 4-4: Energy profile of forward bias. ........................................................................................ 7 Figure 4-5: I-V characteristics of a diode. ......................................................................................... 8 Figure 4-6: (a) Schematic representation of a diode and (b) its complete model, which is a combination of the small and large signal models of a diode. ............................................. 10 Figure 4-7 : (a) Forward bias model and (b) Reverse bias model .................................................... 10 Figure 4-8: HSpice netlist for obtaining I-V characteristic of diode ................................ ................ 12 Figure 4-9: I-V characteristics of diode d1 in Figure 4-8 for temperatures of 27 ºC and 127 ºC ...13 Figure 4-10: Piecewise linear voltage transfer characteristic with break points at (-1 V, -1 V), and (1 V, 1 V) ....................................................................................................................... 14 Figure 4-11: Circuit realization of piecewise linear voltage transfer characteristic with break points at (-1 V, -1 V), and (1 V, 1 V). Vt is a 0V voltage source, whose current controls the CCVS H 1 . ......................................................................................................... 15 Figure 4-12: HSpice netlist for obtaining piecewise linear transfer characteristic shown in Figure 4-10 ........................................................................................................................... 16 Figure 4-13: I-V sketch of a diode. .................................................................................................. 17 Figure 4-14: (a), (b), (c) and (d) for pre-lab exercise 3. R 1 = 1 K. The signal source has a frequency of 5 kHz and amplitude of 3V. ................................................................... 19 Figure 4-15: Circuit schematic for Lab exercise 1 ............................................................................ 20 Figure 4-16: Circuit schematic for Lab exercise 3 ............................................................................ 21
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University of Southern California. EE348L page4 Lab 4 4 Experiment #4: Diodes 4.1 Introduction Diodes are among the most common electronic devices used in circuit design. Qualitatively, basic diode operation is best understood by a valve analogy. An ideal valve permits uninhibited fluid flow in one direction (provided the fluid provides some minimum force to open the valve) while preventing flow in the reverse direction. The ideal diode permits uninhibited current flow in one direction (provided some minimum positive voltage is applied to force the diode into conduction) while limiting reverse current flow to a very small leakage current (provided the negative voltage i sn’t as great as to cause the diode to enter breakdown). These “electrical valves” find utility in numerous applications: rectification, which enhances the average value of a signal and can be used in power supplies; voltage references, in which a desired voltage is achieved as some multiple of the diode breakdown voltage; voltage regulators, in which an
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