mk penguattr1dc
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TRANSISTOR
SEBAGAI FUNGSI PENGUAT
(Analisa DC)
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On = saturasi
Off = cut off
AB
C
Gb.1 Kurva karakteristik output transistor CE
ANALISA DC 1
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Current & Voltage Analysis Consider below figure. Three dc currents and three
dc voltages can be identified
IB: dc base current
IE
: dc emitter currentIC: dc collector currentVBE: dc voltage across base-
emitter junctionVCB: dc voltage acrosscollector-base junctionVCE: dc voltage from
collector to emitter
Transistor bias circuit.
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Collector Current (IC)
The ratio of IC to IE is called alpha (), values
typically range from 0.95 to 0.99.
E
C
I
I
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Base Current (IB) IB is very small compared to IC;
The ratio of IC to IB is the dc current gain of a
transistor, called beta ()
The level of beta typically ranges from about
50 to over 400
B
C
I
I
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Current & Voltage Analysis
When the BE junction is forward-biased, it islike a forward-biased diode. Thus; (Si = 0.7, Ge
= 0.3)
From HVK, the voltage across RB is
By Ohms law;
Solving for IB
BEBBR VVV B
BBR RIV B
B
BEBB
BR
VVI
V7.0VBE
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Current & Voltage Analysis The voltage at the collector is;
The voltage drop across RC is
VCE can be rewritten as
The voltage across the reverse-biased CB
junction is
CCR RIV C
CRCCCEVVV
CCCCCERIVV
BECECB VVV
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Transistor as Amplifier
Transistor is capable toamplify AC signal :(output signal > inputsignal)
Eg: Audio amplifier thatamplify the sound of aradio
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Transistor Amplifier Circuit Analysis
There are 2 analysis;
DC Analysis
AC Analysis Transistor will operate when DC voltage
source is applied to the amplifier circuit
Q-point must be determined so that thetransistor will operate in active region (can
operate as an amplifier)
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DC LOAD LINE (Example)
VCC = 8V
RB = 360 k
RC = 2 k
Draw DC Load Line and Find Q-point.
Answers;
mA
k
V
R
VI
CE
sat
VC
CCC 4
2
8
0
0)(
Coff ICCCCCE RIVV
VVV CCCEoff 8)(
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DC LOAD LINE (Example)
Draw DC Load Line and Find Q-point.
Answers;
Q-point can be obtained by
calculate the half values of
maximum IC and VCE
4V
2 mA
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DC Analysis of Amplifier Circuit
Amplifier Circuit Amplifier Circuit w/o capacitor
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DC Analysis of Amplifier Circuit
Amplifier Circuit w/o capacitor Simplified Circuit
Thevenin Theorem;
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DC Analysis of Amplifier Circuit
Important equation for DC Analysis
1
2
21
21
21//
RR
RRRRR
TH
CCTHV
RRRV
21
2
BC
ETH
BETH
B IIRR
VV
I
;)1(
)(ECCCCCE
RRIVV
1
2
From HVK;
From Thevenin Theorem;
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Contoh 1
Hitung Vc dan tentukan garis bebab DC
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Contoh 2
Dengan hfe = 200, tentukan Rb, Vbb, IB, IC,
IE, Vc, VE dan Vc
VCE= VC VE = 5,03 V
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