EECE 310 Exam 1, Fall 2010

EECE 310 – Quiz 1 – Fall 2010-2011 Page 1 of 6 American University of Beirut Department of Electrical and Computer Engineering EECE 310 – Electronics Quiz 1 – November 5, 2010 Closed Book – No Programmable Calculators 90 minutes There are 20 problems. All problems are equally graded. 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: _________________________________ ID number: _________________ Unless otherwise specified, assume that: VT = 25 mV n = 1 ni = 1.5×1010 cm–3 q = 1.6×10-19 C p p dp J = −qD dx n n dn J = qD dx ( ) d p n J qp qn E μ μ = + I = J × A 0 2 ln A D T i N N V V n ⎛ ⎞ = ⎜ ⎟ ⎝ ⎠ EECE 310 – Quiz 1 – Fall 2010-2011 Page 2 of 6 1. The input voltage to an amplifier is 0.1 V peak-to-peak. Its output voltage is 10.5 V peak- to-peak. The amplifier current gain is 32 dB. Find the amplifier output power (in W) if the amplifier input power is 1 mW. a) 4.2 b) 3.8 c) 2.6 d) 3.0 e) 3.4 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 2. A voltage amplifier is powered by a 12 V battery. The amplifier is loaded by a 16 Ohm resistor. For a sinusoidal output with a frequency of 1 kHz and a peak value of 5 V (and no DC), the efficiency of the amplifier is 25%. Find the power lost in the amplifier (in W). The input signal power is negligible. a) 1.6 b) 1.3 c) 2.9 d) 2.3 e) 1.9 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 3. An amplifier has a linear transfer characteristic passing through the origin (0, 0) and with output voltage saturation at L+ = 9 V and L– = –11 V. The amplifier gain is 200 V/V. What is the amplitude (in mV) of the largest sine-wave input having no dc component that can be applied without causing output voltage distortion? a) 30 b) 50 c) 45 d) 40 e) 35 4. In the previous question, the input voltage now consists of a sine-wave component superimposed over a DC component. The input is adjusted to have the largest possible undistorted sine-wave voltage at the output (around the bias point). What is the value of the input DC component (in mV)? a) 0 b) –15 c) –25 d) 15 e) –5 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 5. Using the load line graphical method, find the operating (bias) point for the diode-like device X in the circuit shown below. The current-voltage characteristics of device X are shown on the ix–vx plot. The x-axis division is 1 V, and the y-axis division is 50 μA. Assume VA = 5 V and R = 16.67 kΩ. If VA increases from 5 V to 7 V, what is the corresponding increase (in μA) in the ix current? a) 170 b) 100 c) 0 d) 235 e) 45 EECE 310 – Quiz 1 – Fall 2010-2011 Page 3 of 6 6. In the previous problem, find the small-signal resistance (in kΩ) of device X at the operating (bias) point, corresponding to VA = 5 V. a) 6.6 b) 3.3 c) 33 d) 330 e) 125 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 7. An amplifier has the transfer characteristic Iv O e v 10 10 40 5 − − = , where Iv > 0 , I O v ≥ v , and both voltages are expressed in V. If the voltage gain is –80 V/V, what is output voltage (in V) at the corresponding operating (bias) point? a) 2.75 b) 2.50 c) 2.00 d) 2.25 e) 3.00 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 8. The free electron concentration in a n-type silicon sample is described by: 4 17 ( ) 10 10 exp( / n ) n x x L = + − free electrons per cm3, where Ln = 1 µm and Dn = 28 cm2/sec. The cross sectional area A of the sample is 200 μm2. Find the diffusion current magnitude (in mA) at x = Ln. a) 3.30 b) 3.06 c) 2.83 d) 2.35 e) 2.59 9. Find the hole density (in cm-3) at x = 0.4Ln in the previous problem. a) 5007 b) 3357 c) 3710 d) 4100 e) 4531 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - EECE 31 In the b 8× 2 V 0.7 V d question 10. Find a) 18.7 11. If th a) 92.70 - - - - - In the c sinusoid D2 and negligib modele while D circuit w 12. Find a) 8.8 13. In th sinusoid a) 6.35 - - - - - 10 – Quiz 1 – battery-charg V, the batte drop when c ns 10 and 1 d the peak i 3 b) 2 he peak diod 0 b) 3 - - - - - - - - circuit show dal signal is D3 have n ble reverse s d by a fixed D1 can be m when OFF. d the increm b) 9 he previous dal variation b) 8 - - - - - - - - Fall 2010-201 ger circuit s ery voltage V onducting, 1. inverse volta 20.14 de current is 36.14 - - - - - - - - wn below, th s superimpo = 1, and ne saturation c d voltage dr modeled by a mental smal 9.9 s problem, f n in V1 is 1. 8.89 - - - - - - - - 11 shown below VB is 6 V, an and by an o age (PIV) o c) 17.31 s 100 mA, f c) 50.28 - - - - - - - - - he power sup osed. Assum egligible rev current. The rop of 0.7 V a fixed volta + - VX R V1 l-signal resi c) 5.5 find the peak .1 V peak-to c) 11.43 - - - - - - - - - w, the sine- nd Rs = 10 open circuit of the diode d) 22.97 find the valu d) 64.42 - - - - - - - - pply V1 has me R = 1.6 k verse saturat e DC charac V when cond age drop of D2 D istance rd1 f d) 6.6 k-to-peak v o-peak. d) 13.97 - - - - - - - - -wave input Ω. The diod when OFF (in V). 7 e) 2 ue of Rc (in 2 e) 7 - - - - - - - - a DC value kΩ. tion current cteristics of ducting, and f 0.8 V when D3 D1 for diode D e) 7 ariation (in 7 e) 1 - - - - - - - - vS has an a de is model . Refer to th 21.56 n Ω). 78.56 - - - - - - - - e of 9 V on t, while D1 f diodes D2 d an open ci n conductin 1 (in Ohms) 7.7 mV) in vol 16.51 - - - - - - - - amplitude of led by a fixe his circuit fo - - - - - - - - which a sm has n = 1.5 and D3 can ircuit when ng, and an op ). ltage VX wh - - - - - - - - Page 4 of 6 f ed or - - - - - mall , and n be OFF, pen hen the - - - - - 6 EECE 31 14. A si of n. a) 1.74 - - - - - 15. The sinusoid mF) in conduct a) 3.26 - - - - - 16. A se shown b 0.1 V fo a) 560 - - - - - The Zen ZK = 0 I 10 – Quiz 1 – ilicon diode b) 1 - - - - - - - - e load resisto dal, with 12 order to lim ting. b) 2 - - - - - - - - eries string below. Each or every dec b) 4 - - - - - - - - ner diode sh mA 3.0 . Ass Fall 2010-201 e is found to 1.56 - - - - - - - - or in a half- 2 V RMS, an mit the ripple 2.41 - - - - - - - - of 3 identic h diode has cade change 460 - - - - - - - - hown below sume X R = 11 o conduct 1 c) 1.39 - - - - - - - - - -wave rectif nd 50 Hz fr e voltage to c) 2.69 - - - - - - - - - cal diodes is a current o e in current. c) 160 - - - - - - - - - w has VZ = 6 580 Ω. Ref mA at 0.70 d) 1.04 - - - - - - - - fier with cap requency. Fi o 0.5 V. Ass d) 2.98 - - - - - - - - s connected f 1 mA at 0 . Find R (in d) 260 - - - - - - - - V 8.6 at ZI fer to this ci 0 V and 10 m e) 1 - - - - - - - - pacitor filte ind the requ sume that th e) 3 - - - - - - - - d through a r 0.7 V and its Ω) required e) 3 - - - - - - - - = 5 mA , w ircuit for qu mA at 0.78 1.22 - - - - - - - - er is 200 Ω. uired capaci he diode dro 3.54 - - - - - - - - resistor R to s voltage dr d to establis 360 - - - - - - - - with = 20 Zr uestions 17 a V. Find the - - - - - - - - The source itance value ops 0.7 V wh - - - - - - - - o a 5 V supp op changes sh Vo = 2.4 - - - - - - - - Ω and and 18. Page 5 of 6 e value - - - - - is e (in hen - - - - - ply as by V. - - - - - 6 EECE 31 17. At n for whic a) 7.24 18. For Zener d a) 5.97 - - - - - 19. In th fixed 0. source v a) 5.8 - - - - - 20. In th 36.8 mW circuit w a) 9 - - - - - 10 – Quiz 1 – no load (RL ch the Zene b) 6 vS = 16 V, diode remain b) 7 - - - - - - - - he circuit sh .6 V drop w voltage vs (i b) 5 - - - - - - - - he circuit sh W. The diod when OFF. b) 8 - - - - - - - - Fall 2010-201 is disconne er diode rem 6.88 what is the ns in the bre 7.57 - - - - - - - - hown below when conduc in V) for wh 5.6 - - - - - - - - hown below de is model Find the va 8 - - - - - - - - 11 ected), what mains in the c) 6.97 value of the eakdown re c) 4.92 - - - - - - - - - w, R1 = RL = cting, and b hich the dio c) 6.0 - - - - - - - - - w R = 480 Ω ed by VD0 = alue of ID (i c) 5 - - - - - - - - - t is the value breakdown d) 7.06 e maximum egion? d) 15.72 - - - - - - - - = 1 kΩ and V y an open c ode conduct d) 5.2 - - - - - - - - Ω and the po = 0.6 V, rD = in mA). d) 6 - - - - - - - - e of the low n region? e) 7 m load curren 2 e) 1 - - - - - - - - V1 = 1.8 V. circuit when ts 1 mA. e) 5 - - - - - - - - ower supplie = 20 Ω, whe e) 7 - - - - - - - - west supply 7.15 nt iL (in mA 10.26 - - - - - - - - The diode i n OFF. Find 5.4 - - - - - - - - ed by the D en conducti 7 - - - - - - - - voltage vS ( A) for which - - - - - - - - is modeled b d the value o - - - - - - - - C source (V ng, and by - - - - - - - - Page 6 of 6 (in V) h the - - - - - by a of the - - - - - VDD) is an open - - - - - 6