ET-210 Quiz 2

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210

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Electrical Engineering

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Apr 3, 2024

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ET 210 Quiz 2 1) Given the following circuit consisting of Silicon diodes D1, D2, D3, and resistors R1, R2, R3, and R4, along with the Vs voltage source: Vs 9V R1 1.8kΩ R4 2kΩ D1 D2 D3 I I I R2 5kΩ R3 2.2kΩ I y s u x I w V a b V V c + _ The definitions of the voltage variables that are labeled (and will be calculated in part e) in the schematic above are: Voltage V a is the voltage across resistor R1 Voltage V b is the voltage across resistor R3 Voltage V c is the voltage across resistor R4 Find the following: a) Determine the bias (forward-biased or reverse-biased) conditions of diodes D1, D2, and D3. All D1, D2, and D3 flows from positive to negative current diode due to the diodes being on. b) Label the current directions with arrows for all of the currents. Label the voltage polarities with plus sign and minus sign pairs for all of the voltages. Use Kirchhoff’s Voltage Law, Kirchhoff’s Current Law, Ohm's Law, and the appropriate diode approximations to calculate the circuit currents and voltages in this problem. Find the following: b) Find the diode voltages V D1 , V D2 , and V D3 (that is, find the voltages across diodes D1, D2, and D3) VD1= VD2= VD3= 0.7V Parts d and e of this problem will be solved together . Find the following: d) Find the currents I S , I U , I W , I X , and I Y (see the circuit shown above for the designations of current variables) IS = 1.725mA IV = 0.17mA, IW = 1.585 mA IX = 1.375mA , IY = 0.35mA e) Find the voltages V a , V b , and V c See the circuit shown above for the designations of voltage variables and :

Voltage variable definitions : Va = IS * 1.8k = 1.725 * 1.8k = 3.105V Vb = IS * 2.2k = 1.725 * 2.2k = 3.795V Vc = IY * 2 = 0.35 * 2 = 0.7V Voltage V a is the voltage across resistor R1 Voltage V b is the voltage across resistor R3 Voltage V c is the voltage across resistor R4 2) Given the following circuit where: D1 is a Silicon (Si) diode D2 is a Germanium (Ge) diode Vs 15V R1 200Ω D1 D2 I I I R2 400Ω y s x + _ Find the following: a) Determine the bias (forward-biased or reverse-biased) conditions of diodes D1 and D2. VD1 = 15V = Forward VD2 = 15V = Forward Both voltages are greater then the cutting voltage so the diode will be forward bias. b) Label the current directions with arrows for all of the currents. Label the voltage polarities with plus sign and minus sign pairs for all of the voltages. Use Kirchhoff’s Voltage Law, Kirchhoff’s Current Law, Ohm's Law, and the appropriate diode approximations to calculate the circuit currents and voltages in this problem. Find the following: c) Find the diode voltages V D1 and V D2 (that is, find the voltages across diodes D1 and D2) VD1 = 0.7V VD2 = 0.3V d) Find the currents I X , and I Y (see the circuit shown above for the designations of current variables) IX = 15-0.7/200 IX = 71.5mA IY = 15-0.3/400 IY = 30mA e) Find the current I S (see the circuit shown above for the designation of the current variable)

IS= IX+ I Y IS = 71.5mA+30mA IS = 101.5mA 3) Given the following circuit consisting of Silicon diodes D1, D2, D3, and resistors R1, R2, R3, and R4, along with the Vs voltage source: Vs 85V R1 4kΩ R3 12kΩ D1 D2 D3 I I I R2 6kΩ s V + _ R4 5kΩ x y r1 V r2 V V r4 V r3 D3 The definitions of the voltage variables that are labeled (and will be calculated in part e) in the schematic above are: Voltages V r1 , V r2 , V r3 , and V r4 are the voltages across resistors R1, R2, R3, and R4 respectively. Voltage V D3 is the voltage across diode D3. Hint: Look carefully at the orientations of the diodes and the polarity of the voltage source when determining the diode bias conditions. Find the following: a) Determine the bias (forward-biased or reverse-biased) conditions of diodes D1, D2, and D3. VD1, VD2 = Forward Bias VD3 = Reverse Bias b) Label the current directions with arrows for all of the currents. Label the voltage polarities with plus sign and minus sign pairs for all of the voltages. Use Kirchhoff’s Voltage Law, Kirchhoff’s Current Law, Ohm's Law, and the appropriate diode approximations to calculate the circuit currents and voltages in this problem. Find the following: c) Find the diode voltages V D1 and V D2 (that is, find the voltages across diodes D1 and D2) and: Find the diode current I D3 (that, is find the current through diode D3, and notice that I D3 = I Y ) ID3= IY = 0

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Parts d and e of this problem will be solved together . Find the following: d) Find the currents I S , I X , and I Y (see the circuit shown above for the designations of current variables) IS = 85 * 1.4/22kOhms = 3.8mA = I2 IS= I X e) Find the voltages V r1 , V r2 , V r3 , V r4 , and V D3 See the circuit shown above for the designations of voltage variables and Voltage variable definitions : Voltages V r1 , V r2 , V r3 , and V r4 are the voltages across resistors R1, R2, R3, and R4 respectively. Voltage V D3 is the voltage across diode D3. VX1 = 3.8*4 = 15.2V VX2 = 3.8*6 = 22.8V VX3 = 3.8*12 = 45.6V VX4 = 0V VD3= v x3 VD3 = 45.6V 4) Given the following circuit where: D1 and D3 are Silicon (Si) diodes D2 is a Germanium (Ge) diode Vs 28V R1 150Ω R2 68Ω D1 D2 D3 I I I s V + _ R3 47Ω x y r1 V V D3 r2 V r3 The definitions of the voltage variables that are labeled (and will be calculated in part e) in the schematic above are: Voltages V r1 , V r2 , and V r3 are the voltages across resistors R1, R2, and R3 respectively. Voltage V D3 is the voltage across diode D3. Hint: Look carefully at the orientations of the diodes and the polarity of the voltage source when determining the diode bias conditions. Find the following: a) Determine the bias (forward-biased or reverse-biased) conditions of diodes D1, D2, and D3. D1 = Forward Biased D2 = Forward Biased D3 = Reverse Biased b) Label the current directions with arrows for all of the currents. Label the voltage polarities with plus sign and minus sign pairs for all of the voltages.

Use Kirchhoff’s Voltage Law, Kirchhoff’s Current Law, Ohm's Law, and the appropriate diode approximations to calculate the circuit currents and voltages in this problem. Find the following: c) Find the diode voltages V D1 and V D2 (that is, find the voltages across diodes D1 and D2) and: Find the diode current I D3 (that, is find the current through diode D3, and notice that I D3 = I Y ) VD1 = 0.7V Silicon Diode VD2 = 0.3V Aluminum Diode ID3= IY = 0A Parts d and e of this problem will be solved together . Find the following: d) Find the currents I S , I X , and I Y (see the circuit shown above for the designations of current variables) IS= I X IY = 0A e) Find the voltages V r1 , V r2 , V r3 , and V D3 See the circuit shown above for the designations of voltage variables and : Voltage variable definitions : Voltages V r1 , V r2 , and V r3 are the voltages across resistors R1, R2, and R3 respectively. Voltage V D3 is the voltage across diode D3. VS- IXR2- VD2- ISR1- VD1 = 0 28 - IS(68) -0.3 - IS (150) - 0.7 = 0 [ IX= IS ] 28 - 0.3 - 0.7 = IS ( 68+150 ) IS = 28-0.3-0.7/68+150 IS = 27/218 IS 123.85mA IX= IS = 123.85mA IY = 0A VX1 = Is R1 = (123.85 * 10^-3) * (150) VX1 = 18.578V VX2= IX R2 = 123.85 * 10^-3 * 68 VX2 = 8.42V VX3 = Iy R3 = 0*47 VX3 = 0V VD3= VX2 = Ix R2 VD3 = 8.42V VS = VD1 + VD2 + VX1 +VXL VS= 0.7+0.3+1.578+8.42 = 28V 5) Given the following circuit consisting of Silicon diodes D1, D2, and resistors R1, R2, along with the + 15 V voltage source and the ‒ 9 V voltage source. R1 4kΩ R2 12kΩ D1 D2 I V x r1 V + 15 V - 9 V Vo r2 The definitions of the voltage variables that are labeled (and will be calculated in part f) in the schematic above are: Voltages V r1 and V r2 are the voltages across resistors R1 and R2 respectively. Voltage V O is the voltage between the Output point and Ground a) Redraw the circuit diagram showing explicit voltage source symbols, resistors, diodes, and the Ground, using the technique from lecture.

Find the following: b) Determine the bias (forward-biased or reverse-biased) conditions of diodes D1 and D2. Reverse bias diode D1 & D2 c) Label the current direction with an arrow for the current I x Label the voltage polarities with plus sign and minus sign pairs for all of the voltages. Use Kirchhoff’s Voltage Law, Kirchhoff’s Current Law, Ohm's Law, and the appropriate diode approximations to calculate the circuit currents and voltages in this problem. Find the following: d) Find the diode voltages V D1 and V D2 (that is, find the voltages across diodes D1 and D2) VD1 = VD2 = 0.7V e) Find the current I X (see the circuit shown above for the designation of the current variable) Apply KVL 15-4*1000I-0.7 -12000I-0.7+920 22.6=16000I IX = 0.001413A f) Find the voltages V r1 , V r2 , and V O See the circuit shown above for the designations of voltage variables and : Voltage variable definitions : Voltages V r1 and V r2 are the voltages across resistors R1 and R2 respectively. Voltage V O is the voltage between the Output point and Ground VR1 = 4000*IN = 5.05V VR2 = 12000 * IN = 16.95V V0 = -V12kN-0.7 + 9 = -16.95 - 0.7+9 = V0 = - 8.65V

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