Download, print and study this document offline |
Page 1 • Energy gap ???? G/si =1.21- 3.6 × 10 -4 .T ev ???? G/Ge =0.785- 2.23 × 10 -4 .T ev ? Energy gap depending on temperature • E F = E C - KT ln? ???? ???? ???? ???? ? = E v + KT ln ? ???? ???? ???? ???? ? • No. of electrons n = N c e -(E c -E f )/RT (KT in ev) • No. of holes p = N v e -(E f -E v )/RT • Mass action law n p = n i 2 = N c N v e -EG/KT • Drift velocity ???? d = µE (for si ???? d = 10 7 cm/sec) • Hall voltage ???? H = B.I w e . Hall coefficient R H = 1/? . ? ? charge density = qN 0 = ne … • Conductivity s = ?µ ; µ = sR H . • Max value of electric field @ junction E 0 = - q ? si N d . n n0 = - q ? si N A . n p0 . • Charge storage @ junction Q + = - Q - = qA x n0 N D = qA x p0 N A • Diffusion current densities J p = - q D p dp dx J n = - q D n dn dx • Drift current Densities = q(p µ p + nµ n )E • µ p , µ n decrease with increasing doping concentration . • D n µ n = D p µ p = KT/q ˜ 25 mv @ 300 K • Carrier concentration in N-type silicon n n0 = N D ; p n0 = n i 2 / N D • Carrier concentration in P-type silicon p p0 = N A ; n p0 = n i 2 / N A • Junction built in voltage V 0 = V T ln ? ???? ???? ???? ???? ???? ???? 2 ? • Width of Depletion region W dep = x p + x n = ? 2e s q ? 1 N A + 1 N D ?(V 0 + V R ) * ? 2???? ???????? ???? = 12.93???? ???????????? ???????? ? • x n x p = N A N D • Charge stored in depletion region q J = q.N A N D N A +N D . A . W dep • Depletion capacitance C j = e s A W dep ; C j0 = e s A W dep / V R =0 C j = C j0 /? 1 + V R V 0 ? m C j = 2C j0 (for forward Bias) • Forward current I = I p + I n ; I p = Aq n i 2 D p L p N D ? ???? ???? /???? ???? - 1? I n = Aq n i 2 D n L n N A ? ???? ???? /???? ???? - 1? • Saturation Current I s = Aq n i 2 ? D p L p N D + D n L n N A ? • Minority carrier life time t p = L p 2 / D p ; t n = L n 2 / D n Analog Circuits gradeu gradeup Page 2 • Energy gap ???? G/si =1.21- 3.6 × 10 -4 .T ev ???? G/Ge =0.785- 2.23 × 10 -4 .T ev ? Energy gap depending on temperature • E F = E C - KT ln? ???? ???? ???? ???? ? = E v + KT ln ? ???? ???? ???? ???? ? • No. of electrons n = N c e -(E c -E f )/RT (KT in ev) • No. of holes p = N v e -(E f -E v )/RT • Mass action law n p = n i 2 = N c N v e -EG/KT • Drift velocity ???? d = µE (for si ???? d = 10 7 cm/sec) • Hall voltage ???? H = B.I w e . Hall coefficient R H = 1/? . ? ? charge density = qN 0 = ne … • Conductivity s = ?µ ; µ = sR H . • Max value of electric field @ junction E 0 = - q ? si N d . n n0 = - q ? si N A . n p0 . • Charge storage @ junction Q + = - Q - = qA x n0 N D = qA x p0 N A • Diffusion current densities J p = - q D p dp dx J n = - q D n dn dx • Drift current Densities = q(p µ p + nµ n )E • µ p , µ n decrease with increasing doping concentration . • D n µ n = D p µ p = KT/q ˜ 25 mv @ 300 K • Carrier concentration in N-type silicon n n0 = N D ; p n0 = n i 2 / N D • Carrier concentration in P-type silicon p p0 = N A ; n p0 = n i 2 / N A • Junction built in voltage V 0 = V T ln ? ???? ???? ???? ???? ???? ???? 2 ? • Width of Depletion region W dep = x p + x n = ? 2e s q ? 1 N A + 1 N D ?(V 0 + V R ) * ? 2???? ???????? ???? = 12.93???? ???????????? ???????? ? • x n x p = N A N D • Charge stored in depletion region q J = q.N A N D N A +N D . A . W dep • Depletion capacitance C j = e s A W dep ; C j0 = e s A W dep / V R =0 C j = C j0 /? 1 + V R V 0 ? m C j = 2C j0 (for forward Bias) • Forward current I = I p + I n ; I p = Aq n i 2 D p L p N D ? ???? ???? /???? ???? - 1? I n = Aq n i 2 D n L n N A ? ???? ???? /???? ???? - 1? • Saturation Current I s = Aq n i 2 ? D p L p N D + D n L n N A ? • Minority carrier life time t p = L p 2 / D p ; t n = L n 2 / D n Analog Circuits gradeu gradeup • Minority carrier charge storage Q p = t p I p , Q n = t p I n Q = Q p + Q n = t T I t T = mean transist time • Diffusion capacitance C d = ? ???? ???? ???????? ???? ? I = t.g ? C d ? I. t? carrier life time , g = conductance = I / ???????? ???? • I 02 = 2 (T 2 -T 1 )/10 I 01 • Junction Barrier Voltage V j = V B = V r (open condition) = V r - V (forward Bias) = V r + V (Reverse Bias) • Probability of filled states above ‘E’ f(E) = 1 1+e (E-E f )/KT • Drift velocity of e - ???? d = 10 7 cm/sec • Poisson equation d 2 V dx 2 = -? v ? = -nq ? ? dv dx = E = -nqx ? Transistor :- • I E = I DE + I nE • I C = I Co – a I E ? Active region • I C = – a I E + I Co (1- e V C /V T ) Common Emitter :- • I C = (1+ ß) I Co + ßI B ß = a 1-a • I CEO = I Co 1-a ? Collector current when base open • I CBO ? Collector current when I E = 0 I CBO > I Co . • V BE,sat or V BC,sat ? - 2.5 mv / 0 C ; V CE,sat ? V BE,sat 10 = - 0.25 mv / 0 C • Large signal Current gain ß = I C - I CBo I B + I CBo • D.C current gain ß dc = I C I B = h FE • (ß dc = h FE ) ˜ ß when I B > I CBo • Small signal current gain ß ' = ?I C ?I R ? V CE = h fe = h FE 1-(I CBo + I B ) ?h FE ?I C • Over drive factor = ß active ß forced ?under saturation ? I C sat = ß forced I B sat Conversion formula :- CC ? CE • h ic = h ie ; h rc = 1 ; h fc = - (1+ h fe ) ; h oc = h oe CB ? CE • h ib = h ie 1+h fe ; h ib = h ie h oe 1+h fe - h re ; h fb = -h fe 1+h fe ; h ob = h oe 1+h fe CE parameters in terms of CB can be obtained by interchanging B & E . gradeup gradeup Page 3 • Energy gap ???? G/si =1.21- 3.6 × 10 -4 .T ev ???? G/Ge =0.785- 2.23 × 10 -4 .T ev ? Energy gap depending on temperature • E F = E C - KT ln? ???? ???? ???? ???? ? = E v + KT ln ? ???? ???? ???? ???? ? • No. of electrons n = N c e -(E c -E f )/RT (KT in ev) • No. of holes p = N v e -(E f -E v )/RT • Mass action law n p = n i 2 = N c N v e -EG/KT • Drift velocity ???? d = µE (for si ???? d = 10 7 cm/sec) • Hall voltage ???? H = B.I w e . Hall coefficient R H = 1/? . ? ? charge density = qN 0 = ne … • Conductivity s = ?µ ; µ = sR H . • Max value of electric field @ junction E 0 = - q ? si N d . n n0 = - q ? si N A . n p0 . • Charge storage @ junction Q + = - Q - = qA x n0 N D = qA x p0 N A • Diffusion current densities J p = - q D p dp dx J n = - q D n dn dx • Drift current Densities = q(p µ p + nµ n )E • µ p , µ n decrease with increasing doping concentration . • D n µ n = D p µ p = KT/q ˜ 25 mv @ 300 K • Carrier concentration in N-type silicon n n0 = N D ; p n0 = n i 2 / N D • Carrier concentration in P-type silicon p p0 = N A ; n p0 = n i 2 / N A • Junction built in voltage V 0 = V T ln ? ???? ???? ???? ???? ???? ???? 2 ? • Width of Depletion region W dep = x p + x n = ? 2e s q ? 1 N A + 1 N D ?(V 0 + V R ) * ? 2???? ???????? ???? = 12.93???? ???????????? ???????? ? • x n x p = N A N D • Charge stored in depletion region q J = q.N A N D N A +N D . A . W dep • Depletion capacitance C j = e s A W dep ; C j0 = e s A W dep / V R =0 C j = C j0 /? 1 + V R V 0 ? m C j = 2C j0 (for forward Bias) • Forward current I = I p + I n ; I p = Aq n i 2 D p L p N D ? ???? ???? /???? ???? - 1? I n = Aq n i 2 D n L n N A ? ???? ???? /???? ???? - 1? • Saturation Current I s = Aq n i 2 ? D p L p N D + D n L n N A ? • Minority carrier life time t p = L p 2 / D p ; t n = L n 2 / D n Analog Circuits gradeu gradeup • Minority carrier charge storage Q p = t p I p , Q n = t p I n Q = Q p + Q n = t T I t T = mean transist time • Diffusion capacitance C d = ? ???? ???? ???????? ???? ? I = t.g ? C d ? I. t? carrier life time , g = conductance = I / ???????? ???? • I 02 = 2 (T 2 -T 1 )/10 I 01 • Junction Barrier Voltage V j = V B = V r (open condition) = V r - V (forward Bias) = V r + V (Reverse Bias) • Probability of filled states above ‘E’ f(E) = 1 1+e (E-E f )/KT • Drift velocity of e - ???? d = 10 7 cm/sec • Poisson equation d 2 V dx 2 = -? v ? = -nq ? ? dv dx = E = -nqx ? Transistor :- • I E = I DE + I nE • I C = I Co – a I E ? Active region • I C = – a I E + I Co (1- e V C /V T ) Common Emitter :- • I C = (1+ ß) I Co + ßI B ß = a 1-a • I CEO = I Co 1-a ? Collector current when base open • I CBO ? Collector current when I E = 0 I CBO > I Co . • V BE,sat or V BC,sat ? - 2.5 mv / 0 C ; V CE,sat ? V BE,sat 10 = - 0.25 mv / 0 C • Large signal Current gain ß = I C - I CBo I B + I CBo • D.C current gain ß dc = I C I B = h FE • (ß dc = h FE ) ˜ ß when I B > I CBo • Small signal current gain ß ' = ?I C ?I R ? V CE = h fe = h FE 1-(I CBo + I B ) ?h FE ?I C • Over drive factor = ß active ß forced ?under saturation ? I C sat = ß forced I B sat Conversion formula :- CC ? CE • h ic = h ie ; h rc = 1 ; h fc = - (1+ h fe ) ; h oc = h oe CB ? CE • h ib = h ie 1+h fe ; h ib = h ie h oe 1+h fe - h re ; h fb = -h fe 1+h fe ; h ob = h oe 1+h fe CE parameters in terms of CB can be obtained by interchanging B & E . gradeup gradeup • A I = -h f 1+h 0 Z L Z i = h i + h r A I Z L A vs = A v .Z i Z i +R s Z i +R s = A I .Z L = A I s .Z L R s A V = A I Z L Z i Y 0 = h o - h f h r h i + R s A Is = A v .R s Z i +R s = A vs .R s Z L Choice of Transistor Configuration :- • For intermediate stages CC can’t be used as A V < 1 • CE can be used as intermediate stage • CC can be used as o/p stage as it has low o/p impedance • CC/CB can be used as i/p stage because of i/p considerations. Stability & Biasing :- ( Should be as min as possible) • For S = ?I C ?I Co ? V B0,ß S ' = ?I C ?V BE ? I C0,ß S '' = ?I C ?ß ? V BE,I Co ?I C = S. ?I Co + S ' ?V BE + S '' ?ß • For fixed bias S = 1+ß 1-ß dI B dI C = 1 + ß • Collector to Base bias S = 1+ß 1+ß R C R C +R B 0 < s < 1+ ß = 1+ß 1+ß? R C + R E R C + R E + R B ? • Self bias S = 1+ß 1+ß R E R E +R th ˜ 1+ R th R e ßR E > 10 R 2 • R 1 = V cc R th V th ; R 2 = V cc R th V cc -V th • For thermal stability [ V cc - 2I c (R C + R E )] [ 0.07 I co . S] < 1/? ; V CE < V CC 2 Hybrid –pi(p)- Model :- g m = |I C | / V T r b ' e = h fe / g m r b ' b = h ie - r b ' e r b ' c = r b ' e / h re g ce = h oe - (1+ h fe ) g b ' c Specifications of An amplifier :- gradeup gradeupRead More
|
Explore Courses for Electronics and Communication Engineering (ECE) exam
|