Thermal - Microelectronic Devices and Circuits - Solved Exam, Exams of Microelectronic Circuits

Download Thermal - Microelectronic Devices and Circuits - Solved Exam and more Exams Microelectronic Circuits in PDF only on Docsity! UNIVERSITY OF CALIFORNIA, BERKELEY College of Engineering Department of Electrical Engineering and Computer Sciences EE 105: Microelectronic Devices and Circuits Fall 2009 MIDTERM EXAMINATION #1 Time allotted: 45 minutes NAME: STUDENT ID#: INSTRUCTIONS: 1. SHOW YOUR WORK. (Make your methods clear to the grader!) Specially, while using chart, make sure that you indicate how you have got your numbers. For example, if reading off mobility, clearly write down what doping density that corresponds to. 2. Clearly mark (underline or box) your answers. 3. Specify the units on answers whenever appropriate. SCORE: 1 15 2 415 3 /20 Total /50 PHYSICAL CONSTANTS Description Symbol — Value PROPERTIES OF SILICON AT 300K Electronic charge g 16x10? C Description Symbol Value Boltzmann’s constant = 8.62% 107 Band gap energy Es 1.12eV evi, Intrinsic carrier ni 10° om? Thermal voltage at Vy = 0.026 V concentration a 300K. KTig Dielectric permittivity ES} 1.0x10"* F/cm USEFUL NUMBERS Vy in(10) = 0.060 V at T=300K exp( 30) ~ 107 Electron and Hole Mab in Silicon at 300K & 1400 1200- elactrans dae: 5 B0)- S : . en eS, 00 0 na : Loos if a 100 194 1a? it ap!” s0l% 19 10% Ng §, (oral dopant caaceutration (em) Prob 2{15 pts). Consider a p-n junction diode of Si as shown below: N,= 10" cnv3 Np=10%¢ cm? {a) Find out the built in potential and the depletion width at T=300K. [4 pt] Om wep FRY f y Py . Code Bie po yses By 7 i 7 . “i ¥ ty x é iy i He pM le * gen | (b} Assume that at T=300K a voltage of 0.9 volt is applied across the diode such that the diode is forward biased, How much should the voltage have to be changed if at T=400 K one needs to ensure that the same current is flowing as in T=300K? Assume no change in bandgap due to change in temperature. [5 pt] a rn {c} In this problem we shalf design a diode to meet certain requirernents. We want a total current of 40 A/cm? at a voltage of 0.8 V at T=300K. Half of the current will have to be supplied by holes and half by electrons. Assume the mobility of electrons to be 500 cm’/V-sec and that of holes to be 250 cm?/V-sec. Also assume that the diffusion length for electrons and hales are the same and equal to 10 um. Find out haw you will design your diode, i.e., how you will dope your p and nsides so that the aforementioned requirements are met. [6 pt] / ; 2 Ae we woke ge YT 2 2 : mA & a “ dl , h df ‘ hey oebe bm LR BEAM a . oe wo EY a tS i sos mete os “j wees pr be a boon : ¢ ‘ es » ~ REN ‘A ype Git phon i % vis de . . “0 i VF Ty : é i HL \ . ty € Vi L . Fae da Ry Prob 3. [20 pts}Bipatar junction transistors. (a) Design Fundamentals [4 pts} (i) Why is the base region doped more lightly than the emitter? [2 pt] Piet @ AGS ow IY foevi t ¢ Ei EVE SEA UP {ii} Why is the width of the base region narrower than emitter and collector regions? [2 pt} t pet ye, ee ys Lost fay fi yu teense F : {b} Write dawn the condition for active made operation and saturation mode operation for a NPN bipolar junction transistor. Consider the following transistor that has B=100. If itis desired that 1 mA current must be flowing in the collector at Vce=1 V, what is the maximum vatue for RL that can be used before the transistor goes from active ta saturation mode? [Spt] melita be? ¥ tok Q. <r P=l60 AO ay av , Iv i | aé " va Sei RAE