ECE 3040C| MWF 12:05 – 1:25 | Fall 2011 Instructor: Azad Naeemi | MiRC 216 | azad@.gatech.edu

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ECE3040C

Microelectronic Circuits Final Exam Wednesday, Dec. 14, 2011. Student Name:

1. In terms of the lattice constant a, what is the distance between nearest neighbor atoms in (5 points)

(a) a bcc lattice? (b) an fcc lattice? 2. What are the Miller Indices for this plane? (5 points)?

ECE 3040C| MWF 12:05 – 1:25 | Fall 2011 Instructor: Azad Naeemi | MiRC 216 | azad@.gatech.edu

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3. You dope a piece of Si with phosphorus with a density of 1014 atoms per

cm-3. What will be the density of majority and minority carriers? The intrinsic carrier density in Si at 300K is 1010cm-3 (5 points)

4. Let’s assume a thin piece of n-doped semiconductor is shined with light

and the generation rate of GL=1013 per cm3 per second is uniformly created in its entire volume. The minority carrier lifetime is 1μs. What would be the minority and majority carrier densities if the doping concentration is 1015 per cm3? (Note: Low-level injection assumption is valid here.) (10 points)

ECE 3040C| MWF 12:05 – 1:25 | Fall 2011 Instructor: Azad Naeemi | MiRC 216 | azad@.gatech.edu

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5. The minority carrier density in the base of a BJT is plotted below. Is the

base transport factor close to zero or to 1 and why (5 points)?

6. In a half-wave rectifier, you use a diode that can tolerate a maximum of

20V reverse voltage. What is the maximum voltage that this rectifier can provide (5 points)?

7. What is the advantage of a bridge rectifier over a half-wave rectifier (5

points)?

ECE 3040C| MWF 12:05 – 1:25 | Fall 2011 Instructor: Azad Naeemi | MiRC 216 | azad@.gatech.edu

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8. What is the voltage V in this circuit (10 points)? Are D1 and D2 forward

or reverse biased and why?

ECE 3040C| MWF 12:05 – 1:25 | Fall 2011 Instructor: Azad Naeemi | MiRC 216 | azad@.gatech.edu

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9. In an npn BJT, VBE=0.7V and VBC=-5V (10 points). A. In what region is this BJT biased?

B. If we change VBC to -10V, what will happen to Ic (increase or decrease)? Why?

10. How can you make a current source? Draw the circuit and explain what

condition you must satisfy to have a good current source (5 points).

ECE 3040C| MWF 12:05 – 1:25 | Fall 2011 Instructor: Azad Naeemi | MiRC 216 | azad@.gatech.edu

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11. In the circuit below, we want to bias the MOSFET in the saturation region and ID=1mA (20 points). Assume μnCox = 200 μA/V2, W/L=5, VTH = 0.4V and λ = 0, VDD=4V, and R1=R2=100 kΩ.

What should be Rs? (10 points) a. What is the maximum value of RD to stay in the saturation region? (10 points)?

ECE 3040C| MWF 12:05 – 1:25 | Fall 2011 Instructor: Azad Naeemi | MiRC 216 | azad@.gatech.edu

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12. The differential amplifier shown below has the following parameters: VCC

12 V, VEE = 10.7 V, REE = 100 kΩ, RC = 600 kΩ and βF = 100 (15 points) (a) Calculate the Q-point for the transistors in the amplifier circuit.

(b) Draw the half circuit for differential mode.

ECE 3040C| MWF 12:05 – 1:25 | Fall 2011 Instructor: Azad Naeemi | MiRC 216 | azad@.gatech.edu

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(c) Calculate the differential mode gain.

13. In the circuit below, what is the output voltage in terms of the input voltages V1 and V2, assuming that the OpAmp is ideal and R1=R2=0.1R3 (5 points)