EECE 310 Exam 2, Fall 2008

EECE 310 – Electronics – Quiz 2 – Fall 2008-2009 - Page 1 of 7 American University of Beirut Department of Electrical and Computer Engineering EECE 310 – Electronics Quiz 2 – December 19, 2008 Closed Book – No Programmable Calculators 90 minutes Penalty is 5 to 1 (1 to 4 wrong answers do not result in a penalty; 5 to 9 wrong answers cancel one correct answer; 10 to 14 wrong answers cancel two correct answers; and so on) Name: _________ANSWERS________________ ID number: _________________ EECE 310 – Electronics – Quiz 2 – Fall 2008-2009 - Page 2 of 7 An N-channel MOSFET with k’ = 1 mA/V2 is biased such that it is operating in the saturation region. The Early voltage for this MOSFET is VA = 5 V. When the MOSFET is biased at VOV = 1 V, with VDS = VX Volts, the drain current is 1 mA. When the overdrive voltage increases to 1.2 V, VDS decreases by 20% to 0.8×VX while the drain current increases to 1.2 mA. 1. Find the initial value of VDS (VX in V). a) 35 b) 32.5 c) 27.5 d) 25 e) 30 2. Find the value of (W/L) for this MOSFET. a) 1/6 b) 1/7 c) 1/4 d) 1/3 e) 1/5 ▬▬▬▬▬▬▬▬ 3. If a P-channel MOSFET is biased at VGS = –9 V and VDS = –1 V, and has a threshold voltage Vt = –3 V, find its region of operation. a) Triode (Linear) b) Saturation c) Cutoff d) Pinch-Off e) Unknown ▬▬▬▬▬▬▬▬ 4. Consider the two-stage amplifier shown below. What should be the value of G (in mA/V) to achieve a voltage gain vo/vi of 700? a) 7.5 b) 4.5 c) 5.25 d) 6 e) 6.75 5. Find the output resistance (in KΩ) of the amplifier (set the input to zero, and use the definition of output resistance). a) 94 b) 34 c) 7.06 d) 10 e) 24 6. If G = 3 mA/V, what is the short-circuit transconductance io / vi (in mA/V), when the 20K load resistance connected across the output is set to zero (replaced by a short circuit)? a) 21.2 b) 31.8 c) 42.4 d) 52.9 e) 63.5 ▬▬▬▬▬▬▬▬ EECE 310 – Electronics – Quiz 2 – Fall 2008-2009 - Page 3 of 7 The drain current of an enhancement N-channel MOSFET is measured at several values of VGS, VDS, and VSB, as shown in the table below. For this MOSFET, | 2φf | = 0.6 V. VGS (V) VDS (V) VSB (V) ID (mA) 3 3 0 3.6 3 4 0 4.2 4 1 0 IX 4 4 0 9.45 4 4 4 6.6703 7. Find the value of Vt0 (in V). a) 0.9 b) 0.8 c) 0.6 d) 0.7 e) 1.0 8. Find the value of k’(W/L) (in mA/V2). a) 0.9 b) 1.4 c) 1.1 d) 1.2 e) 1.3 9. Find IX (in mA). a) 3.77 b) 3.92 c) 2.25 d) 3.24 e) 2.86 10. Find the value of VA (in V). a) 4 b) 3 c) 5 d) 10 e) 7 11. Find the value of γ (in V1/2). a) 0.35 b) 0.4 c) 0.5 d) 0.3 e) 0.45 ▬▬▬▬▬▬▬▬ EECE 310 – Electronics – Quiz 2 – Fall 2008-2009 - Page 4 of 7 The MOSFET in the circuit below has the iD – vDS characteristics shown in Figure A. The curves correspond to the following values of VGS: 1, 2, 3, 4, and 5 V. Assume that VDD = 5 V and RD = 2.2 KΩ. iD (mA) 0 1 2 3 4 5 1 2 3 4 5 6 vDS(V) Figure A 12. Find the y–axis intercept of the load line. a) 2.27 b) 5 c) 4.17 d) 3.33 e) 2.78 13. Find VDS (in V) at the bias (Q) point of the MOSFET when VGS = 4 V. a) 2.4 b) 1.8 c) 0.8 d) 3.2 e) 1.2 ▬▬▬▬▬▬▬▬ EECE 310 – Electronics – Quiz 2 – Fall 2008-2009 - Page 5 of 7 14. Find the drain current (in mA) for the MOSFET in the circuit below. The MOSFET parameters are Vt0 = 1 V, k’(W/L) = 1 mA/V2, and VA = 4 V. Assume VGS = 3 V, VDD = 9 V and RD = 1 KΩ. a) 0.39 b) 1.44 c) 2.85 d) 4.33 e) 5.70 ▬▬▬▬▬▬▬▬ 15. Find VGS (in V) for the MOSFET in the circuit below. The MOSFET parameters are Vt0 = 0.8 V and k’(W/L) = 0.2 mA/V2. Assume RS = 0.5 KΩ. a) 3.67 b) 4.37 c) 3.99 d) 3.27 e) 3.02 9V 3.3K 1000K RS 1000K ▬▬▬▬▬▬▬▬ EECE 310 – Electronics – Quiz 2 – Fall 2008-2009 - Page 6 of 7 16. The drain current for the MOSFET in the circuit shown is given by VDD/2R. The MOSFET threshold voltage is –VDD/8. Find the product k’(W/L) × VDD × R. a) 6.6 b) 11.1 c) 9.0 d) 7.84 e) 7.1 R VDD ▬▬▬▬▬▬▬▬ 17. Assume in the circuit below that vi is a small voltage, not exceeding a few milliVolts. Find the value of (W/L) for the MOSFET, if it is required to have vo/vi = 0.5 when VGG = 1.8 V. The MOSFET parameters are Vt0 = 0.6 V and k’ = 0.1 mA/V2. a) 4.76 b) 3.70 c) 11.1 d) 8.33 e) 6.25 ▬▬▬▬▬▬▬▬ 18. A MOSFET amplifier is biased at VOV = 0.1×VDD, VDS = 0.5×VDD. Find the product gm×ro for this MOSFET, if VA = 4×VDD. a) 150 b) 170 c) 90 d) 110 e) 130 ▬▬▬▬▬▬▬▬ EECE 310 – Electronics – Quiz 2 – Fall 2008-2009 - Page 7 of 7 In the circuit shown below, the MOSFET is biased such that gm = 1 mA/V and ro = 50 KΩ. Assume that all capacitors are very large, and that R = 220 KΩ. 19. Find the overall small-signal voltage gain vo/vsig. a) –3.28 b) –3.89 c) –4.76 d) –5.14 e) –5.42 20. Find the input resistance vi/ii in KΩ. a) 28.7 b) 110 c) 89.2 d) 40.7 e) 68.8 21. Assume that the gain from gate to drain vo/vi is –8. What is the maximum signal swing (in V) at the drain that keeps the MOSFET in saturation? The transistor is biased at VOV = 0.8 V, VDS = 3 V. Neglect signal distortion. a) +/–2.13 b) +/–1.42 c) +/–1.6 d) +/–1.78 e) +/–1.96 ▬▬▬▬▬▬▬▬ 22. The process transconductance parameter k’ is 0.2 mA/V2 for a certain process. If the dielectric thickness tox is reduced by a factor of 2, find the new value of k’ (in mA/V2). a) 0.5 b) 0.4 c) 0.3 d) 0.2 e) 0.1 ▬▬▬▬▬▬▬▬ 23. A MOSFET is biased at VOV = 1 V, VDS = 3 V, with ID = 0.2 mA. Find the resistance value (in KΩ) that appears between gate and source in the small-signal T-model. a) 1.67 b) 2.0 c) 5.0 d) 3.33 e) 2.5