Question 3 (20 Marks) Lab 1-Zener Circuits and Applications Theory: Zener diode is designed to…

Question 3 (20 Marks) Lab 1-Zener Circuits and Applications Theory: Zener diode is designed to operate in reverse conduction. Zener breakdown occurs at a precisely defined voltage, allowing the diode to be used as a voltage reference or clipper. While Zener diodes are usually operated in reverse conduction, they may also be operated in cutoff and forward conduction. There are two different effects that are used in “Zener diodes”. The only practical difference is that the two types have temperature coefficients of opposite polarities. a. Zener breakdown Occurs for breakdown voltages greater

»Question 3 (20 Marks) Lab 1-Zener Circuits and Applications Theory: Zener diode is designed to operate in reverse conduction. Zener breakdown occurs at a precisely defined voltage, allowing the diode to be used as a voltage reference or clipper. While Zener diodes are usually operated in reverse conduction, they may also be operated in cutoff and forward conduction. There are two different effects that are used in “Zener diodes”. The only practical difference is that the two types have temperature coefficients of opposite polarities. a. Zener breakdown Occurs for breakdown voltages greater than approximately 6V when the electric field across the diode junction pulls the electrons from the atomic valence band into the conduction band, causing a current to flow b. Impact ionization (also called avalanche breakdown) Occurs at lower breakdown voltages when the reverse electric field across the p-n junction causes a cascading ionization, similar to an avalanche, that produces a large current. Zener Diode V Zener diode ratings include: Zener Voltage (Vla Power Dissipation (Pa) Max Current (lm) Zener Impedance (Za) Max Leakage Current (lVR) Temperature Coetficient (az Figure 3: I-V Curve of a typical Zener Diode A reference diode is a special Zener diode designed to use both conduction modes, which cancels the temperature coefficients and produces a temperature stable breakdown voltage Zener diode ratings include a. Zener Voltage (Vz@) b. Power Dissipation (Pa) c. Max Current (I) d. Zener Impedance (Z) e. Max Leakage CurrIR@VR) f Temperature Coefficient (avz) The model for a reverse biased Zener diode (on the left side of the Figure 4) can be represented as a series circuit consisting of a regular diode with voltage drop V, a bias voltage source to provide a total drop of Vz across the Zener diode terminals, and a resistor to represent the Zener impedance (Rf represents the slope of the reverse conduction V-I curve). For this lab, we will neglect the effects of Ra.The forward biased Zener diode would simply be a regular diode (on the right side of the Figure 4) 1. IN4001 diode 1 pcs 2. IN4732A diode 1 pes 3. 470 2-1 pcs 4.10k O-1pcs 5. Crocodile clip cable 6. DC Power supply 7, Oscilloscope with 2 probes with build-in function generator or 8. Oscilloscope with 2 probes with separate unit Function Generator 1.By using i N4001 diode. 470 O and 10k O resistor, construct a clipper circuit as shown in Figure 7 2. Set your power supply to output 4.1 V that will be used as bias in this circuit 3. Ensure your function generator is set to high impedance (or Hi-Z) output. 4. Set your function generator to generate RAMP waveform to output a -2.5 V to +2.5 V rise over 5 ms. Feed the waveform to the clipper cuit as V(t). 5. Connect channel 1 of the Oscilloscope to V(t) and channel 2 to the Vo(t). 6. Set the horizontal scale of the scope to 200 ms/div and vertical scale to 5 Vidiv 7. Draw the waveforms displayed on the scope to your TMA 8. Next, remove diode IN4001 and the DC Power Supply. Replace it with IN4732A as shown in Figure 8. 9. Under the same settings on the scope and function generator, draw the new waveform displayed on the scope to your TMA 10. Overlay both waveforms in this lab into 1 single graph below Diode 1N4001 Resistor1 R-470 Ohm V AC Resistor2 Vi + DC Vdc-4.1 V Figure 7: Diode clipper circuit Resistor1 R-470 Ohm ADS Diode Model 1N4732 V AC Vi Resistor2 R-10kOhm Vo Figure 8: Zener Diode Clipper circuit 1. Explain the working principle of clipper circuit. 5 marks] [5 marks] [5 marks] 2. Draw the waveform you observed on the screen of the scope in step 9 and 11 above Compare the waveform observed with the simulated results. 3. From the waveform you observed, what is the output clipping voltages and Vi where the output waveform begins to clip? 4. Explain the purpose of setting the DC Power Supply to 4.1 V in the diode clipper circuit? Appendix 5 marks IN4001 Data sheet-attached in a separate file IN4732A Data sheet attached in a separate file.

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