DE LA SALLE UNIVERSITY - DASMARINAS
Dasmarinas, Cavite, Philippines
COLLEGE OF ENGINEERING, ARCHITECTURE AND TECHNOLOGY ENGINEERING DEPARTMENT DEPARTMENT
ASSIGNMENT NO. 1 COMPILED BY: CABUDSAN, SARAH FATIMA FATIMA C. C.
1st Semester, 2014-201
S!B"EC# I$S#%!C#O%: ENGR. KATRINA ACAPULCO
AUGUST 1, 2014
The Bipolar Junction Transistor or BJT was invented in 1948 at Bell Telephone Laboratories, New New Jersey, Jersey, US! US! "t was the #irst #irst $ass produced transistor, ahead o# the %&S #ield'e##ect transistor (%&S)*T+ by a decade! The The ter$ ter$ bipo bipola larr re#e re#ers rs to the the #act #act that that both both elec electr tron ons s and and hole holes s are are involved in the operation o# a BJT! BJT! The $inority carrier di##usion di##usion plays the leadin role role -ust as in the .N -unction -unction diode! The word -unction -unction re#ers re#ers to the #act that .N -unctions are critical to the operation o# the BJT! BJT! BJTs BJTs are also si$ply /nown as bipolar transistors! BJT is $ade o# a heavily N'type doped e$itter, a .'type base, and an N'type collector! This device is an N.N BJT! ( .N. BJT would have a .'e$itter, N'type base, and .'type collector!+ collector!+ N.N transistors e0hibit hiher trans conductance cond uctance and speed than
.N. transistors because the electron $obility is larer than the hole $obility! BJTs are al$ost e0clusively o# the N.N type since hih per#or$ance is BJTs co$petitive ede over %&S)*Ts! bipolar -unction transistor is #or$ed by -oinin three sections o# se$iconductors with alternatively di##erent dopin! .hysical structure o# BJT2 •
Both electrons and holes participate in the conduction process #or
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bipolar devices! "t consists o# two .N -unctions constructed in a special way and
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connected in series, bac/ to bac/! The transistors have 3'ter$inal devices with e$itter, base and
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collector ter$inals! BJTs divided into two roups2 N.N and .N. transistors!
%odes o# operation2 • • • •
Two -unctions o# BJT can be either #orward or reversed'biased! "t can operate in di##erent $odes dependin on the -unction bias! "t can operate in active $ode #or a$pli#ier circuits! Switchin applications utilie both the cuto## and saturation $odes!
&peration o# the N.N transistor in the active $ode, as e$itter is heavily doped, a lare nu$ber o# electrons di##use into the base (only s$all #raction co$bine with holes+!
"# the base is thin these electrons et near the
depletion reion o# B5 -unction and are swept into collector i# 6 5B 7 ! &peration o# the N.N transistor in the saturation $ode, both *BJ and 5BJ are #orward biased, the carrier in-ection #ro$ both e$itter and collector into
base! Base $inority carrier concentration chane accordinly to leadin o# reduced slope as 6B5 increases! Saturation $ode divides into 3 roups2 •
So#t Saturation ' di##usion current is s$all and " very close to its
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active'$ode level eep Saturation :eion ' it is s$aller than its active'$ode level Near cut'o## ' close to ero
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The .N. transistor is the analo to N.N BJT! 5o$pare to a N.N, .N. current directions are reverse and the voltae subscripts switched! Li/e the cut'o##, *B is a reversed biased! The active, *B id a #orward biased and 5B is a reversed biased! nd the deep saturation, *B is #orward while 5B is reversed biased!
http2;;aries!ucsd!edu;NJ%B";5LSS;*5*<=;<'>;N&T*S;BJT1!pd# http2;;www!eecs!ber/eley!edu;?hu;5hen$in'@uAch8!pd# http2;;cc!ee!ntu!edu!tw;?lhlu;eecourses;*lectronics1;*lectronicsA5h4!pd#