ECE 311 lab report 5

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Electrical Engineering

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Dec 6, 2023

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Laboratory Report 5 ECE 311-L01 By Phu Trinh Partner: Furkan Mohamed Prof. Thomas Wong TA: Zi Wang Due date: 03/22/2022

Introduction In this lab, a new circuit analysis known as the PSpice will be introduced. PSpice is a circuit simulate software that is very useful that allow user to easily set up different circuits using various components and observe their characteristic. Through this lab, essential circuits that use diode as major building block such as the half-wave rectifier, the peak rectifier, and the limiter circuits would be analyzed using PSpice software. Pre-lab prediction 1. a) As a constant diode current, the voltage drop across diode decreases by about 2mV for every 1 o C increase in temperature. Thus, if the temperature increases, the diode curve will compress horizontally. b) Using small-signal analysis, forward diode resistance r d = V T I D , so if the current running through the diode increase, the value of r d will decrease => Forward resistance of diode lower at high current.

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Schematic Figure 1: diode test circuit (circuit 5.2) Figure 2: Half-wave Rectifier (circuit 5.12)

Figure 3: Peak Rectifier (circuit 5.14) Figure 4: Limiter Circuit (circuit 5.15) Waveform Part 1

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Figure 5: output of diode test circuit (diode curve); breakout voltage set at -150V Figure 6: diode forward bias I-V plot (25 o C) Figure 7: diode forward bias I-V plot (50 o C)

Part 2 Figure 8: output of half-wave rectifier circuit Figure 9: output of peak rectifier circuit Part 3 Figure 10: Peak rectifier (V dc = 5V)

Figure 11: Peak rectifier (V dc = 3V) Analysis Figure 5 shows the I-V characteristics of diode. On the left part of the plot is the forward bias region, showing that as the voltage across diode gets over certain point, the current running through that diode will approach infinity. On the right part of the plot is the reverse bias region, showing that as the voltage across diode goes pass the breakout voltage, the current running though diode will approach infinity; in other words, if the voltage across diode passes breakdown voltage, the diode will conduct current in the reverse direction. In figure 6, the zoom in of diode forward bias plot, the diode voltage drop value is about 720mV. That voltage drop value is the value measured at 25 o C. In figure 7, where the temperature is changed to 50 o C, the plot is compressed horizontally, making the diode voltage drop value to be about 680mV. In other word, as temperature increase, the diode voltage drops across diode decrease. This is consistent with the prediction made in the prelab. In figure 8, the output of the half-wave rectifier, the shape of the output waveform is the same as the shaped predicted in the prelab; however, there is a small difference in the peak voltage values. In the prelab, the diode was assumed to be ideal, so there is no voltage drop across the diode, thus the peak voltage value drawn in the prelab waveform is 20V In the PSpice simulator, the diode used to analyze is set up to be as realistic as possible, so there is a small voltage drop across the diode. If taking that voltage drop to account, the peak voltage value of the output will not be 20V but slightly less than that (about 20V – 0.7V = 19.3V). The same is true for the output waveform of the peak rectifier circuit, and V out max of the peak rectifier circuit is about 10V – 0.7V = 9.3V. In addition, it can be observed in figure 9 that the output waveform of peak rectifier is almost linear. This is an important characteristic of peak rectifier circuit that could be used in transforming AC source into DC source. In figure 10, the output of the limiter circuit, the waveform obtained using PSpice is also the same as the waveform predicted in the prelab, but, like before, the peak voltage and negative

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peak voltage values of the two waveforms are slightly different. In the prelab, the diode is again assumed to be ideal, so V D = 0V, and the output peak positive voltage value is the same as the limiter value V dc , but when using PSpice, the diode voltage is about 0.7V, making the output peak positive voltage equal to V out peak = V dc + 0.7V. Thus, when V dc = 5V, the cutoff line is slightly above 5V in the plot of figure 10. As for the peak negative voltage, in the prelab, when V in < V dc the diode in reverse bias, and to calculate the output voltage the voltage divider formula should be used, but in the prediction the voltage divider was not considered, causing an error in the peak negative value predicted. The peak negative voltage should be 10V * 1000/1100 = 9.09V, and this value is the same as the value obtained in PSpice. When the limiter voltage V dc = 3V, the peak positive voltage is 3V + 0.7V = 3.7V, making the cutoff line to be slightly over 3V in the obtained plot. Possible source of error: -Human error: mistakes when using PSpice, setting up wrong schematic, incorrect circuit elements used, or measuring wrong components. -Instrumental error: software malfunctioned, bug, incorrect representation of components. desired output. PSpice Experience At first it was hard to learn how to use PSpice since the software has too many new components and functionality that can hardly be familiar with in a short time. There were many mistakes while using PSpice, and every mistake can significantly affect the output of the circuit. However, after getting used to PSpice, analyzing circuits and their components become much easier. The software contains many functionalities that are very helpful, making it quicker to obtain results and analyze circuits. Furthermore, the data obtained is very reliable with high precision, assisting in the observation of circuits’ characteristics. Beside some of the functionalities introduced in this lab, there are many other useful tools that can help in analyzing circuit, but it will take some time to become used to everything in PSpice. Conclusion The major characteristics of essential microelectronic circuits that use diode as building block has been studied in the previous lab, but in this lab, with the help of a useful analysis tools called PSpice, the characteristics are observed and analyzed again with higher precision, reflecting more accurate and realistic properties of different circuit components. Overall, the diode’s predicted behaviors and its behavior analyzed using PSpice are the same. There were slight errors and differences between the two, but in analysis those difference could be negligible. PSpice contains a lot of functionalities that are not only useful for analyzing microelectronic circuits but also many other types of circuits.