23a HW p19 MOSFET

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Apr 3, 2024

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2023 Winter EECS 314 HW p19 MOSFET as a switch © 2023 Alexander Ganago Page 1 of 6 Last printed 4/3/23 10:14:00 PM File: 23a HW p19 MOSFET.docx HW p19 (100 points) MOSFET as a switch The data file “23a HW p19 50 ohm data.xlsx” shows the relation ࠵? !" ࠵?࠵?. ࠵? #" for IRF 510 MOSFET with load resistor ࠵? $ = 50 ࠵? and the source voltage ࠵? %% = 6 ࠵?. HW p19 Figure 1. Panel (a) shows the real circuit diagram. Panels (b, c) show simplified circuit diagrams for MOSFET as a switch. (a) (b) (c) Part One (10 points) Approximate circuit analysis Consider HW p19 Figure 1 panel c: MOSFET as an ideal closed switch (zero resistance ࠵? !" ). Calculate the following variables: o The maximal current through the circuit ࠵? in mA Your answer: 120 mA o The maximal power absorbed by the load resistor ࠵? $ in mW. Your answer: 720 mW

2023 Winter EECS 314 HW p19 MOSFET as a switch © 2023 Alexander Ganago Page 2 of 6 Last printed 4/3/23 10:14:00 PM File: 23a HW p19 MOSFET.docx Show your work to get credit. I = V dd /R L = 6/50 * 1000 = 120 mA P L = I 2 * R L = 0.12 2 * 50 * 1000 = 720 mW Part Two (50 points = 10 for each plot) Plots based on the data file “23a HW p19 50 ohm data.xlsx” Use EXCEL to make the following plots vs. the controlling voltage ࠵? #" : o The current through the circuit ࠵? in mA. o Linear vertical axis 0 20 40 60 80 100 120 140 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5 Current(mA) Controlling Voltage V_GS (V) Controlling Voltage vs Current

2023 Winter EECS 314 HW p19 MOSFET as a switch © 2023 Alexander Ganago Page 3 of 6 Last printed 4/3/23 10:14:00 PM File: 23a HW p19 MOSFET.docx o Logarithmic vertical axis o The resistance of the MOSFET (between the Drain and the Source electrodes) ࠵? !" in kΩ. o Linear vertical axis 0.1 1 10 100 1000 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5 Current(mA) Controlling Voltage V_GS (V) Controlling Voltage vs Current 0 10 20 30 40 50 60 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5 ResistanceR_DS(kOhm) Controlling Voltage V_GS (V) Controlling Voltage vs Resistance

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2023 Winter EECS 314 HW p19 MOSFET as a switch © 2023 Alexander Ganago Page 4 of 6 Last printed 4/3/23 10:14:00 PM File: 23a HW p19 MOSFET.docx o Logarithmic vertical axis o On the same plot – the power absorbed by the load ࠵? $ and the power absorbed by the MOSFET ࠵? !" , both in mW; linear vertical scale. 0.001 0.01 0.1 1 10 100 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5 ResistanceR_DS(kOhm) Controlling Voltage V_GS (V) Controlling Voltage vs Resistance 0 100 200 300 400 500 600 700 800 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5 PowerAbsorbed(mW) Controlling Voltage V_GS (V) Controlling Voltage vs Power Absorbed P(MOSFIT) P(Load)

2023 Winter EECS 314 HW p19 MOSFET as a switch © 2023 Alexander Ganago Page 5 of 6 Last printed 4/3/23 10:14:00 PM File: 23a HW p19 MOSFET.docx Part Three (15 points = 5 points for each calculation + 5 points for the discussion) Compare the results calculated with EXCEL and your results of approximate circuit analysis in Part One Calculate the % difference [(calculated at ࠵? #" = 6 ࠵? ) – (expected from approximate analysis)] for each of the variables: o The current through the circuit ࠵? Your answer: 6.50% % difference = (120 – 112.2)/120 * 100 = 6.50% o The power absorbed by the load resistor ࠵? $ Your answer: 4.27% % difference = (720 – 689.2532916)/720 * 100 = 4.27% Briefly discuss whether the approximate circuit analysis (in Part One) makes sense, and why. The approximate circuit analysis makes sense because we are assuming the MOSFET does not have resistance and acts as a closed switch. This means we can calculate the expected maximal current through the circuit and the maximal power absorbed by the load which will be slightly more than the measured values.

2023 Winter EECS 314 HW p19 MOSFET as a switch © 2023 Alexander Ganago Page 6 of 6 Last printed 4/3/23 10:14:00 PM File: 23a HW p19 MOSFET.docx Part Four (25 points) MOSFET as a switch From your EXCEL file, calculate the ratio: &’()* ,-.’*-)% -/ 01) 2’,% *).3.0’* ,0 4 !" 56 4 &’()* ,-.’*-)% -/ 01) 2’,% *).3.0’* ,0 4 !" 57 4 = 689.253292/0.00063012 = 1093844.49 Briefly discuss whether MOSFET is a good switch MOSFET is a good switch. For the sake of simplicity, assume the following: o MOSFET acts as an open switch at the controlling voltages ࠵? #" ≤ ࠵? 8 when the power absorbed by the load resistor is < 5% of the maximal power calculated in Part One. o MOSFET acts as a closed switch at the controlling voltages ࠵? #" ≥ ࠵? 9 when the power absorbed by the load resistor is > 95% of the maximal power calculated in Part One. Use the date from your EXCEL file to fill the table below: Controlling voltage ࠵? 8 , volt Controlling voltage ࠵? 9 , volt The interval ࠵? 9 − ࠵? 8 , volt 3.454545 5.151515 1.69697 From your EXCEL file, calculate the ratio: ࠵?࠵?࠵?࠵?࠵?࠵?࠵? ࠵?࠵?࠵?࠵?࠵? ࠵? !" ࠵?࠵?࠵?࠵?࠵?࠵?࠵?࠵? ࠵?࠵? ࠵?ℎ࠵? ࠵?࠵?࠵?࠵?࠵?࠵? ࠵?࠵?࠵?࠵?࠵? ࠵? $ ࠵?࠵?࠵?࠵?࠵?࠵?࠵?࠵? ࠵?࠵? ࠵?ℎ࠵? ࠵?࠵?࠵?࠵? ࠵?࠵?࠵?࠵?࠵?࠵?࠵?࠵? ࠵?࠵? ࠵? #" = 6 ࠵? × 100% = ࠵?࠵?. ࠵?࠵?% Ratio = 179.5430494*100/689.2532916 = 26.05% Briefly compare MOSFET as a switch with an ideal switch, which has the following features: o It absorbs zero power o It immediately switches between the open and closed positions. MOSFET is comparable to an ideal switch because the power absorbed by the MOSFET reaches zero when it acts as a closed switch. It also switches between open and closed positions as shown in the graphs.

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