Basics of Semiconductor 1(Solutions for Vol 1_Classroom Practice Questions)

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2 hater Basics of Semicouctor (Solutios for ol _lassroom Practice Questios) 0. As: (a) 3 N 50 cm 9 0 = cm 3 Accorig to mass actio law i i N i ( N ) i N = cm 3 0. As: (b) Accorig to law of mass actio. i Where i = itrisic carrier cocetratio. N = oig cocetratio for a - tye material. Majority carrier cocetratio N N i N 03. As: (b) = 5 L = 00 mm = 3800 cm /-sec = 800 cm /-sec = E 3800 L = 900 cm/sec 04. As: () For the -tye semicouctor with = N a i / N, the hole cocetratio will fall below the itrisic value because some of the holes recombie with electros 05. As: (c) 5 0 N A.6 accetor / cm = 4000 cm /-sec = 000 cm /-sec = q = N A q ( 00% oig efficiecy) = 0. mho/cm As: () Accorig to mass actio law. i i N A i i N i 07. As: (a) H = m 3 /c = m AE Egg. Publicatios Hyeraba elhi Bhoal Pue Bhubaeswar Begaluru Luckow Pata heai ijayawaa izag Tiruati Kukatally Kolkata

3 Let us cosier -tye semicouctor H q q H = m 3 AE Egg. Publicatios As: (b) At equilibrium No. of e esity = No. of hole esity give e esity is (x ) = 0 (x ) (x ) is majority (x ) is miority P(x ) = 0P(x ) 09. As: (b) 30 3 m = 0. m /-sec H = 60m q P = m 3 H q = 360 m 3 / 0. As: (b) J rift = qe + P qe J rift = [(.q) + (.q) ]E : 3 : Postal oachig Solutios J rift = [ + ] J harge cocetratio. As: (c) = 0 cm /s = 600 cm /s kt T q 0 T.5 m 600. As: () ouctivity of a semicouctor, ( P )q Where, µ mobility of electros µ mobility of holes electro cocetratio hole cocetratio q electro charge 3. As: (c) N A = E E N kt l Hyeraba elhi Bhoal Pue Bhubaeswar Begaluru Luckow Pata heai ijayawaa izag Tiruati Kukatally Kolkata Fi F A i l.50 = e 0.37 e 0 4. As: (b) Give, wires W & W = where = iameter of wire L = 4L where L = legth of wire 6

4 : 4 : Electroic evices & LS elatio betwee resistaces of W & W.L L r A r.l 4L L 4 L L L L L 4L = 5. As: (c) Hall voltage, H is iversely roortioal to carrier cocetratio H P P H P P H H 7. As: (a) itrisic semicouctor, No. of e = No. of holes 8. As: (a) P-tye, as oig icreases hole cocetratio icreases. Accorig to i mass actio law electro cocetratio ecreases. 9. As: (b) itrisic semicouctor, electro hole airs are geerate ue to exteral eergy true. electro mobility is to 3 times more tha hole mobility true. Both the statemets are true but statemet is ot a correct exlaatio of statemet 0. As: (a) Both (A) a () are true, () is the correct exlaatio of (A) 6. As: (b) kt q T 3 9 = m /sec iffusio legth, L = 300 -tye B Eg B P-tye B Eg B = m AE Egg. Publicatios Hyeraba elhi Bhoal Pue Bhubaeswar Begaluru Luckow Pata heai ijayawaa izag Tiruati Kukatally Kolkata

5 hater 0. As: (c) + N PN Juctio ioe 04. As: (c) ma = GO (e G T T ) = SO (e ) S GO SO e e 0.78 /(0.06) = /( 0.06) 4000 = E P +, + iicates heavily regio a iicates lightly oe regio. 0. As: (a) w = q 0 N w = 0 w 0 w = m w = 4 m. N A 0.8 ( 7.) 0.8 (.) 05. As: (c) a PN Juctio ioe the yamic couctace g m, g m i.e. g m 06. As: () i v characteristic of the ioe i v 0.7 A, v () From the give circuit, Loo equatio : v = i, v () k i v T 03. As: (a) AeP LP AE Egg. Publicatios 0 Ae L P P ep A L o Ae L o P =.9 ma/cm Elimiatig v from () a () : i i i i, i A 6. ma As: (b) Give, = T = m Hyeraba elhi Bhoal Pue Bhubaeswar Begaluru Luckow Pata heai ijayawaa izag Tiruati Kukatally Kolkata

6 : 6 : Electroic evices & LS = ma 08. As: (a) Give 3 Give T = 40 T =? 3 5 T T 5 0 T T 0 T T 0 T T As: (b) For either Si (or) Ge.5 m/ 0 T To maitai costat curret 700m =.5 0 o o = 650 m 660 m 0. As: (b) = 0 r A = 0 r A = 6 00 = 0 F T T = 50 T = 50 +T T = 90 AE Egieerig Acaemy Hyeraba elhi Bhoal Pue Bhubaeswar Luckow Pata Begaluru heai ijayawaa izag Tiruati Kukatally

7 3 hater Zeer ioe 0. As: () s = 00 s = 30 0 = 0 Power issiatio = s s 0 = 00 = W 0. As: (c) Power ratig of Zeer ioe = 5 mw ` Z Z Z ma 5 : urret flows through the circuit is = ma 0 5 Z 5K m 03. As: (b) L =50mA L +0 Z 0 = 5 Z e Give that, z = 6 zmi = 5mA mi L max mA = zmi + Lmax Lmax = 75 ma z 6 L mi L max 04. As: (b) ve cycle of i/ ioe forwar biase, so relace by short circuit, so o/ = i/ with i o/ oly otio b exists, so usig metho of elimiatio aswer is b. 05. As: () Give circuit, + 5 Give, source voltage s = Lmi = 00 ma Lmax = 500 ma z = 5 z mi = 0A 00mA to 500mA 0 + Z L s z zmi 5 500mA Lmax AE Egg. Publicatios Hyeraba elhi Bhoal Pue Bhubaeswar Begaluru Luckow Pata heai ijayawaa izag Tiruati Kukatally Kolkata

8 : 8 : Electroic evices & LS K i = = As: (c) Give circuit, 0 = = As: (a) The ieal characteristic of a stabilizer is costat outut voltage with low iteral resistace 08. As: (a) PN juctio ioe break ow ees o oig. As oig icreases breakow voltage ecreases. Zeer ioe breakow is less tha 6 t has Negative Temerature coefficiet (oerate i. B) Avalache ioe breakow greater tha As: (b) A is correct a is correct but is Not the correct exlaatio of A because voltage stabilizer circuit ca be imlemete by usig other comoets like O-Am also. There is o ee that oly Zeer ioe to be use. AE Egieerig Acaemy Hyeraba elhi Bhoal Pue Bhubaeswar Luckow Pata Begaluru heai ijayawaa izag Tiruati Kukatally

9 4 hater Secial Purose ioes 0. As: (a) Tuel ioe t is highly oe S. ( : 0 3 ) t is a abrut juctio (ste) with both sies heavily oe mae u of Ge (or) GaAs t carries both majority a miority currets. t ca be use as oscillator Oerate i Negative esistace regio Oerate as fast switchig evice 0. As: (c) The values of voltage ( ) across a tuelioe corresoig to eak a valley currets are P a resectively. The rage of tuel-ioe voltage for which the sloe of its - characteristics is egative woul be P < 03. As: (c) Schottky ioe is mae of metal a semicouctor to ecrease the switchig times, hece it ca be use for high frequecy alicatios. 04. As: (a) Symbol ircuit ame LE Tuel ioe aractor ioe Alicatios irect Ba ga Fast Switchig circuits Electroic Tuig 05. As: (a) The tuel ioe has a regio i its voltage curret characteristics where the curret ecreases with icrease forwar voltage kow as its egative resistace regio. This characteristic makes the tuel ioe useful i oscillators a as a microwave amlifier. AE Egg. Publicatios Hyeraba elhi Bhoal Pue Bhubaeswar Begaluru Luckow Pata heai ijayawaa izag Tiruati Kukatally Kolkata

10 5 hater Biolar Juctio Trasistor 0. As: (b) = /(+) = = = /0.995 = As: () = 4mA r 0 0k A r0 A 0k A > 0k A > A > As: () A = 00 = ma E = 0 Q E = A f A = Q = Q = 0 00 = ma 04. As: (b) The heomeo is kow as Early Effect i a biolar trasistor refers to a reuctio of the effective base-with cause by the reverse biasig of the base-collector juctio. AE Egg. Publicatios 05. As: (a) Give = 0.995, E = 0mA, co = 0.5mA EO = ( + ) BO EO BO EO = (+99) EO = 00A 06. As: (b) BO is greater tha O. everse leakage curret ouble for every Te egrees rise i temerature. 07. As: (b) Give base with W B = cm Base oig N B = 0 6 cm 3 r 0 = & = 0 F/cm qn W B B uch Hyeraba elhi Bhoal Pue Bhubaeswar Begaluru Luckow Pata heai ijayawaa izag Tiruati Kukatally Kolkata uch As: (a) = 0.98 B = 40 µa BO = µa For a E active BJT = B + (+) BO = =.0 ma 6

11 : : Electroic evices & LS 09. As: (b) BO = 0.4 µa EO = 60 µa EO = (+) BO EO BO 60 = = 50 = = As: (c) ariatio of base with ue to reverse biase voltage across collector - base juctio is kow as Early Effect. E. As: (b) Juctio E - B - B egio of oeratio F. B F.B Saturatio egio F.B.B Active egio.b F.B verse active egio.b.b ut-off egio 3. As: (c) High ower trasistors are mae of Si to withsta high temerature : Silico is a iirect ba ga material. EB + W B + B B As B icreases, effective base with (W B ) ecreases. As: (a) A a are correct a is the correct exlaatio of A. At very high temerature, extrisic semicouctors will behave as itrisic i.e., charge carriers will remais costat. AE Egg. Publicatios Hyeraba elhi Bhoal Pue Bhubaeswar Begaluru Luckow Pata heai ijayawaa izag Tiruati Kukatally Kolkata

12 hater 6 Juctio Fiel Effect Trasistor 0. As: () G 4. to 4.4. ma to.6 ma g m GS (.6.) = m As: () s rai curret remais costat at ich off regio eve if the rai voltage icreases. 0. As: (c) gs = t = 0 gs = As: (b) max = ss = 0 ma P = 4 GS = gs SS AE Egg. Publicatios GS P = SS = 5.65 ma t 4 SS 05. As: (c) JFET acts as a voltage cotrolle curret source 06. As: (a) Mobility of electro is higher tha mobility of hole Si Electro mobility : 350 cm / v s Hole mobility : 450 cm / v s Ge Electro mobility : 3600 cm / v s Hole mobility : 800 cm / v s : Low leakage curret meas high iut imeace : everse bias icreases, chael with reuces (wege shae) 07. As: (c) P = 8 SS = ma From the give circuit, G = 5 S = 0 GS = 5 Hyeraba elhi Bhoal Pue Bhubaeswar Begaluru Luckow Pata heai ijayawaa izag Tiruati Kukatally Kolkata

13 : 3 : Electroic evices & LS S at which ich off regio meas ( S ) mi = GS P = 5 ( 8) = = As: () P. oltage cotrolle evice FET (3) Q. urret cotrolle evice BJT (). ouctivity moulatio evice-- MPATT ioe (4) S. Negative couctace evice -UJT () 09. As: () SS = ma P = 6 GS = 0 S = 7 At GS = 0, = SS = ma GS SS P 0. As: () evice : Alicatio A. ioe ectifier (3) B. Trasistor Amlifier (). Tuel Oscillator () ioe. Zeer eferece ioe oltage (4). As: (a) 3 SS 50 g m0 = 5 0 G. As: (b) BJT is curret cotrolle curret source ( i = 0 ; o = ) Gai B.W is high FET is voltage cotrolle curret source ( i = ; o = 0) Gai B.W is low UJT is a egative resistace evice a ca be use as a oscillator UJT ca be use as switch but ca t be amlificatio 3. As: (a) FET majority carriers oly exist. BJT majority & miority carriers exist. 4. As: (a) S N chael FET ut resistace of FET is of the orer of tes (or) hures of mega ohms (Ms) : gs is reverse bias. : reverse bias very small leakage curret O flows through the gate AE Egg. Publicatios Hyeraba elhi Bhoal Pue Bhubaeswar Begaluru Luckow Pata heai ijayawaa izag Tiruati Kukatally Kolkata

14 hater 7 Otoelectroic evices 0. As: (a) By KL, P = 0 P = = 0. P = r P r =. 0. As: (b) f illumiatio ouble the curret assig through the hoto ioe is ouble =.8 = 3.6mA oltage across hoto ioe is = = = r r AE Egg. Publicatios = = As: (b) Avalache hoto ioes are referre over PN ioes i otical commuicatio because Avalache hoto ioes are (APs), extracte from avalache gai a excess oise measuremet a higher sesitivity. PN ioes geerate more oise. 04. As: (c) Photo ioe always oerates i reverse bias. Whe o light falls o hoto ioe, Small amout of reverse saturatio curret flows through the evice calle ark curret. 05. As: (a) Give, E g =. e,; =. m = 0.87 m; E g =? A E g E g E g E g Hyeraba elhi Bhoal Pue Bhubaeswar Begaluru Luckow Pata heai ijayawaa izag Tiruati Kukatally Kolkata E =.46 e g E g As: (a) Sesitivity of hoto ioe ees o light itesity a eletio regio with. 07. As: () 4.8 = A = 7.07 ma As: (c) Photo ioe oerate i.b: Photo ioe works o the ricile of hoto electric effect.

15 : 5 : Electroic evices & LS 09. As: (b) oltage across PN juctio ioe resultig i curret which i tur rouce hotos a light outut. This iversio mechaism also calle ijectio electro lumiescece observe i LE s. 0. As: (b) = 890 A o.40 E G = 3.93 e m. As: () Solar cell coverts otical (sulight) eergy ito electrical eergy. 3. As: () LE: F.B Photo ioe:.b Zeer ioe:.b Oriary ioe: F.B Tuel ioe: F.B ariable caacitace ioe:.b Avalache ioe:.b 4. As: (c) Tuel ioe is always oerate i forwar bias a light oerate evices are oerate i reverse bias. (Avalache hoto ioe). 5. As: (b) LE s a LASE s are use i forwar bias. Photo ioes are use i reverse bias.. As: (b) = 0.45 A/W P 0 = 50 µw P P0 P = P 0 = =.5 µa Loa curret = P + 0 =.5 µa + µa = 3.5 µa AE Egg. Publicatios Hyeraba elhi Bhoal Pue Bhubaeswar Begaluru Luckow Pata heai ijayawaa izag Tiruati Kukatally Kolkata

16 8 hater MOSFET 0. As: (c) T = S = 5 = 4 GS = 3 = GS T = = S > GS T 4 > Saturatio 0. As: () active regio (or) saturatio regio, chael is iche off. Number of carriers reset i the chael ecreases from source e to rai e ue to otetial icreases from source to rai. 03. As: () K [ GS T ] K [ ] GS [ ] ma [ ] 4mA T = 0 holes As: (b) ) sice it has -tye source & rai, it is -chael MOSFET. ) rai curret flows oly whe GS >, it imlies it has threshol voltage ( th ) of + t is ehacemet tye MOSFET. 3) Th = + W 4) g m ox GS Th, L trascouctace ees uo electro mobility. 06. As: (b) si A sbo = 0 m si = rsi 0 = F/m 04. As: () A = sq m = 0 m = m = 0 6 m N = 0 9 /cm 3 i = 0 0 No. of holes = cocetratio volume olume = A = 0 8 m 0 i holes / cm 00 holes / No. of holes = m A = (0.) + (0.) + (0.) = 3(0.) = m sbo sbo = ff AE Egg. Publicatios Hyeraba elhi Bhoal Pue Bhubaeswar Begaluru Luckow Pata heai ijayawaa izag Tiruati Kukatally Kolkata

17 : 7 : MOSFET ractical, this ca will rovie to frot a back sies also the area may be A = (0.60 ) + (0.) + (0.) A = m sbo As: (a) L ov = = 0 m = 0 m, w = m rsi =.7, rox = = F/m ox ov = ox w L ov w L t rox t ox 0 w L ov ox ov 6 7fF 00 = = 0.69 ff 0.7 ff 9 si e A A si A As: (b) Th = 0.5 G = 3 (0 Pich-off occurs whe = G Th = =.5. As: (a) M M )cm 0.857m 08. As: (a) A = 0 4 cm si = 0 F/cm ox = F/cm 0 = 7 F ox A 0 ox A t t ox AE Egg. Publicatios ox 3 ox A 70 0 = 50 6 cm = 50 m 09. As: (b) 0 F F = 7.75 olts A A 0.5 Hyeraba elhi Bhoal Pue Bhubaeswar Begaluru Luckow Pata heai ijayawaa izag Tiruati Kukatally Kolkata 0A 3

18 hater 9 Biasig Biasig 04. As: (b) A aalysis, + 0. As: (c) self bias GS = S GS SS P GS =.06 S 0 3. K.5mA GS SS GS As: (b) G = GS + S mA.8K G S G GS 5.4 ( ).68K 4.4m i Z i = M, 05. As: (a) Z i SS 00 3 GS Z 0 0K K Z 0 8 KL at outut loo, M gs S 0 K 5.65mA 3 S 0 = 8.75 g m gs 0K K Z 0 out 03. As: (c) S = ( + S ) = 30 4 ma(3.3k +.5K) S = 0.8 AE Egg. Publicatios 06. As: (b) (By Pritig Mistake i olume- Aswer (c) is wrog, orrect aswer is (b)) By observig, The circuit is commo rai i.e., source follower circuit. Hyeraba elhi Bhoal Pue Bhubaeswar Begaluru Luckow Pata heai ijayawaa izag Tiruati Kukatally Kolkata

19 : 9 : Postal oachig Solutios 0. As: (b) A v(b) = 0 log 0 A v i S g m = 0.0S m = 0 m 0 50 = 0 log 0 A v A v 0 (5 / ) As: Hz 00K Small sigal equivalet r 0 s g m = 0 M 00 K 00 = 00 G g S g m gs r L s 0. As: () P = FEQUENY ANALYSS 0 L 0 0 =.5 0 A i A v (B) = 0 log 0 A v 0 = 0 log 0 A v A v = 0 = i 0.5 i P 0 = 30W L = 5 s gm gs g, Av A v = mi-ba, gai = g m (r L ) = 6.66 f H eq F eq eq eq 6.66 =. F eq = +. = 3. F, eq = 8.33k f H = Hz r L = 8.33k AE Egg. Publicatios Hyeraba elhi Bhoal Pue Bhubaeswar Begaluru Luckow Pata heai ijayawaa izag Tiruati Kukatally Kolkata

20 : 0 : Electroic evices & LS MOSFET BASNG 6 S 0. As: (b) T = 0.8 K = W W 40 L L m 0 5 M W L S M W L 4 o x W ox L GS ox = +5 0 GS G S GS W L 0 T GS = 0 0 = 0 W W L L 0 =.5 0. As: (a) W L W GS T GS L 40 (4. 0 ) = 5( 0 0.8) 03. As: (c) 0 =.9 T m T x t 5 4(5 x t ) GS G (5 x t ) (x t ) 04. As: -7 r ge x x = 3 g m gs G s G g m gs r s x r b // L // L 0//0K = 0K From figure S = S. 0x W L GS = 0x W L GS t t A gmr r g s r m. 50K 0K 0K K 0K 5mA /.0K.K 7.04 s AE Egg. Publicatios Hyeraba elhi Bhoal Pue Bhubaeswar Begaluru Luckow Pata heai ijayawaa izag Tiruati Kukatally Kolkata

21 : : Postal oachig Solutios 05. As: () g m s i g m s () g m g () i m () () s = 06. As: (c) SS = 6 ma P = 3 GSQ = s + i + SS GS P = ma From the give circuit S = 0.75 k = = 8 GSQs = G S = G = S + = M = 0 M AE Egg. Publicatios Hyeraba elhi Bhoal Pue Bhubaeswar Begaluru Luckow Pata heai ijayawaa izag Tiruati Kukatally Kolkata

22 0 hater MOS & evice Techology 0. As: (c) A B E After otio (c) as above aswer 0. As: (a) x x 03. As: () 04. A B. clk y A B. y A B A B 05. As: (b) N f P Q OUT 8 0 sec 0 sec evice Techology Key + 0. (c) 0. (b) 03. No Aswer 04. (b) 05. (a) O/P P Q AN gate AE Egg. Publicatios Hyeraba elhi Bhoal Pue Bhubaeswar Begaluru Luckow Pata heai ijayawaa izag Tiruati Kukatally Kolkata