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Advanced Mid24

imp questions on advanced semiconductors but for the mid

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20 views22 pages

Advanced Mid24

imp questions on advanced semiconductors but for the mid

Uploaded by

ggogo2181
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Put (T) on the true statement or (F) on the false statement, Your answers for the false statements are not evaluated unless you provide the correct statement [1.0 Mark for each statement] 1. In the boundaries of the quasi-neutral regions of a PN junction (0) .p(0) = ni 2, In the linearly graded PN junction, the doping concentration changes gradually at the metallurgical junction. At no bias, equilibrium is reached when Ja(x) + Jp(x) = 0 in a PN junction. 4. For the PN junetion, 5, There is no electric field aeross the space charge region at no bi Put ('T) on the true statement or (F) on the false statement. Your answers for the false statements are not evaluated unless you provide the correct statement. [0.5 Mark for each statement] The magnitude of the electric field in the space charge region of a PN junction diode is proportional to Np if Nos N ‘The electric field is zero in the quasi-neutral regions of a biased PN junction. Zener Breakdown occurs in heavily doped PN junctions, The reverse saturation current of the diode decreases by increasing temperature In the piece-wise linear approximations of the diode characteristics with Vj-0 and finite Ry the static resistance of the PN junction is equal to the dynamie resistance In the transition region of a PN junction f (x Jax Put (7) on the true statement or (F) on the false statement. Your answers for the false statements are not evaluated unless you provide the correct statement, 10.5 Mark for cach statement] A contact difference of potential is formed in a PN junction even if the doping concentration changes fadually around the metallurgical junction. ‘The electric field is zero in the quasi-neutral regions of a biased PN junction. Avalanche Breakdown occurs in heavily doped PN junctions. ‘The reverse saturation current of the diode decreases by increasing temperature. In the picce-wise lincar approximations of the diode characteristics with V;=0 and finite Ry the stati resistance of the PN junction is equal to the dynamic resistance. In the tansition region ofa PN junction [ p(x Jae True or False. Your answers for the ou provide the correct ‘statement. [0.5 Mark for each statement] ‘occurs in heavily doped PN junctions. s by increasing temperature. -ases in a P* N junction with increasing the n-doping concentration, ssimations of the diode characteristies with V;-0 and finite Ry -qual to the dynamic resistance mmetrical BUT, @, =a,and fe “ A short circuit B-E junction is able to collect majority carriers injected from a forward biased B-C junction. .. Put (T) on the true statement or (F) on the false statement. Your answers for the false statements are not evaluated unless you provide the correct statement, [1 Mark for each statement] 1. A contact difference of potential is formed in a PN junction even if the doping concentration changes gradually around the metallurgical junction. ‘The magnitude of the electric field in the space charge region of a PN junction diode is proportional to Ny if M n-tyPe — OF = YNMn = YN Mn PE Ph eT olsen oa 2 LR eR oR Ci aS Nar a LCOS oer eae fol hen ee Wye On Na. iD ro DLs eax) » Tere) errs SCRE fey) Question 2: (6 Marks) De:17-4 & pal ne aun ii. , Faos = Pays NPs = ni? /Naz eho ae y Sal Lane ro Pao } ers read a) i. x Ce eae ' rhe x a A TCT a ce —_— Brea aan i) Sip ta ae rea = pea ii) Ge Aye apace rs py iB) : ee One Nai iy La Go= Bee CREA By a ee a B-baxto® = ra Pree Cea Ot Sr Oca Le ae Ee atv an Pe rvs ANTES EY YIU al Ob) alc) re a F rr AGW ACO NT eT AND $o=0-Fhv, TS ata PNY eT) Cea (a) = ae Pee its Te aca BOS ae ie 1) Ne a em Baar oS GeO MEE ata ein en eee ew ras Pata rt —— o Tear Se Cir a i) —_—— Cee ee OR PELE AEA iC Prey eee sae = 62 ice a oe PPL Rt oo ‘Qaction (8 Mari) | Cons the NPN polar asso shown below: The rash he flowing amet oof Sich and label te exes iy cai pofles hen ah jt ae award is wit = Vy Wy. (2M) Calculate th foward cure, ff hs device wen tiie inte fwad ave ei. Pg tani $0. (Maris) Redesign hits nce te forward cent ain, 100y insite dping el aoe the herein vc Ind ego shuld cane ano wh the edi evel stole [2M TB inctease Fp, inctease Noe te incteose Up. & Pp =loo__y orp = 0- 9800990059 F Oly 1s Corshiad Bp = Ot Or © Consider an NPN bipolar transistor biased in the Forward Active mode. Draw the Ebers—Moll model. [2 Marks} Derive an equation for the base current, Zs, in terms of ar ax, Fes, and Ics, and the applied voltages. [2 Marks} Let the base terminal be open so I= 0. Show that, when a collector-emitter voltage is applied, we have C= ava) eto = ese = -( ter) + « = -b Ip +%g +e? ples ee a ‘usin elavhe bas ichangst Cis he cos onc and xh hy Mast [ Aad ‘Question 2: (5 Marks) Consider two PN junctions at 7300 K, having exactly the same electrical and physical parameters except for the bandgap energy of the semiconductor materials. The first PN junction has a bandgap energy of 0.525 eV and a forward- bias current of 10 mA with V,= 0.255 V. For the second PN junction, “design” the bandgap energy, E, so that a forward- bias voltage of Vi= 0.32 V will produce a current of 10 A. Bo b. Draw the small signal model of the PN junction, Derive the expressions of the model elements. [4 Marks] ¢. Draw the energy band diagram and carriers’ distribution of a PNP Bipolar Junction Transistor with Vzx> 0 and Ven <0. [4 Marks] = Uge>0, Veg So —* Fareed Active 2 Transition capacitance Qj (coulombs) = AgN,ly = AgNalp 4 r= $2 Dynamic resistance 3. Dittusion capacitance Ho” Sra vis = Pole) te) Page Loft » Op = 4 Jo'nlx) dx 3 Cp ate = Lh geal He Dp dq AT tA) Op , Wr oLp nL = a, * dy = Cbp * Con = yr ( tp + trIn ) Qvestion (8 Marks) Vin silicon PN Cates ‘Sksch he hem equilib energy-bnd gr, nd Pot the ec vers ditanc ough the jencton Da serene vlog sich hat the igh dope mcm silly pleted a Vos AE dhuenol Xplibe — Ys 107 Va = 2.74 96Y [Mack Mars] 11 Mack [2 Marks) = 0-9bHY HO em 2 O-BSAU pw 08644 fam b. The electric field within the space charge region of a PN junction is given below: E (<105Viem) i. Where is the junction located? [2 Marks] ii, Assuming depletion approximation, sketch the doping profile on the N and P-sides of the junction. [3 Marks] No=1.94 x10" exn® Na=3.23 x10" eam 110% com Marks) The Ammete eu following figures 0 pa 1. Determi diode given thot Vi~ 0.0259 V. fi. Ifthe batery is reversed estimate the diode current assuming that Vj=0.6V and R=. Then ca Aitfusion capacitance piven that Ips (Assume P'N junetion diode) eer nny OIL Dee eee se?) ii) In= -0-6 = o-ymA , ¢ eel Gia) Raa ook = vet )eaeete 22-1 a ro Yaa Ci-opoe Jes Le - M1 = Ta, fe =] FA] are alee ~ “ples * Tes Te pee Testa teri] J = 10 ep (zs =A.6gsrto” cas + Mier Course wjecbes AP. QE = 107 vole oS elFe,73 Ae’s 4 ap (ps Spe qe oly (yoo they). 028g 2a! + Bele Ninrclions Gj. Ls at ea Si Semple corhelsly obec thucchen 2 Be Sartor = 0.888 - | Gi) beh re illuerttons Ret Le an Mee Nameadions = Sts SL 4 ~ FIS20l, (oo = Fh,23 Rreedoge “Jo For a uniformly doped siioon PN junction diode with an N-ype doping of 10% em? and a Paype doping of 2<10" em, answer the following questions (10 Marks} Draw the energy-band diagram ofthe PN junction at equilibrium and show al the relevant eneray wales, Determine the total depletion width andits faction onthe N and P-sides respectively at equilibrium, Where will most of the depletion width lie i the P type doping is much larger than the N-type doping? Sketch the electric field within the space charge region and determine its maximum valu. By what factor will he maximum electric fel increase ifthe doping in both N and P-regions is doubled?” Sketch the potential within the space charge region at equilibrium. What fraction ofthe built-in ‘voltage is dropped in the N-region? Where will most of the bul-in voltage be dropped i the P type doping is much larger than the N-type doping? Determine the magnitude ofthe depletion width and maximum eletic Field when the PN junction is reverse bitsed by 2 V. Draw the energy band diagram ‘a, An abrupt silicon PN junction at T'= 300 K is uniformly doped with Nq = 2 x 10 em” and Np = $ x 10! em, ‘The cross-sectional arca of the PN junction is 8 x 10" em?. An inductance is placed in parallel with the PN junction, i. With a reverse biased voltage of Mx= 10 V applied to the PN junction, the resonant frequency of the circuit is (f-1.25 MHz. What is the value of the inductance? [4 Marks} 1i, Using the results of part (i), what is the resonant frequency ifthe reverse-biased voltage is Va=1'V__ [3 Marks] D) GS Cee aL) oan oe zu ERE ° ay O2er eed a A a YE Ia (MO so = a ris i) Ge ANU re ea aro DeNe le) rata 4 7 i) Snp = (No-nee) All a foe Par A 9 aes it} TP vr ee DR een aD Gey Tr we ra i) Noa ap ulad Aad Po , lav ’ ny UL Peery aS J903)~Dne +d eo - Te(3) a, Use the Ebers-Moll model to determine fc foran NPN BJT biased at 19=100 nA and Var= 0.628 V. The Ebers- Moll model parameters are Les 1.25%10 A. and fes=2.5x10"" A and ay=0.996, Assume ar les an Ics i. Determine the collector current. 15 Marks] Hi. Compare the collector current to base current Fatio computed in (i) to fir. [3 Marks} wv peed Ot ees) Tey [-Tes wales ies res => Voc= 0-528V [

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