P226. Lecture 5. 4/16/2019Transistor (transconductance resistor) is a three terminal device to switch or amplifier signals.
NPN transistor pup transistor
Idea
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Currentmode smallcurrentinduces
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Rules for NPN transistor
Collector is more positive than Emitter.1.Base-emitter and base-collector are effectively diodes.2.I_collector = beta I_beta. Beta can be as high as 60-1003.Constraints: I_base, I_collector and V_ce should not be too high.4.
Typically I_collector < 0.1~1 A and V_ce < 15~40V.Model of a NPN transistor: Applications:
Switch1.
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Impedance change lookat thepurplecircle
inputimpedance ReminderZ n 0V.in 0Iin Vout
inAioutRlaiinBtl R
Inputimpedance improvedby 11
Reminder thehighertheinput impedance thebetter
Transistor as a current source
Outputimpedance lookat theorangecircle
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PtiExtension
DarlingtonPair c
p 4 furtherimprovecurrent
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Transistor as an amplifier:
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ak tierWhatdoweassumehere k vin o.br
AcgainGac 8Vo 8Vin
Example design a transistoramplifier with Gao 10
for aweaksignal with a powersupply 10k
step1 make sure it can amplifyV l0V 8Vout 1282CM A Rosie
Gkn 10K R8V.in rVontVint Fortin 108Vin
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So we should biasVinby say IV and thus
ie o.lt 1k o4mA.Voutisbiasedby6VVout
6 10Vin
A complete Ac friendly circuit
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Our first non trivial circuit.H
