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Transistors &
Opamp
Ms.S.M.Hosamani. Assistant Professor
Department of E&TC PICT, Pune.
17 September 2019 1
Contents
• Transistor (BJT) Structure
• Transistor characteristics and parameters
• DC operating point
• Transistor as an amplifier
• Transistor as a switch
• MOSFET
• Operational Amplifier
17 September 2019 2
Introduction
• The semiconductor device like a diode cannot amplify a
signal, therefore its application area is limited.
• The next development of semiconductor device after diode is a
BJT (bipolar junction transistor).
• It is a three terminal device. The terminals are – collector,
emitter, and base. Out of which the base is a control terminal.
• A signal of small amplitude applied to the base is available in
the “magnified” form at the collector of the transistor.
• Thus the large power signal is obtained from a small power
signal. 17 September 2019 3
http://www.bellsystemmemorial.com/belllabs_transistor.html
History of Transistors
1948 – The year of establishment of E&TC - COEP
17 September 2019 4
Why is it called transistor ?
• The term transistor was derived from the words TRANSFER & RESISTOR.
• Transfers input signal current from a low resistance path to a high resistance path.
17 September 2019 5
N-P-N transistor
N
N
P
C
E
B
Collector Base Junction JC
Emitter Base Junction JE
E Emitter
B Base
C Collector
17 September 2019 6
The BJT – Bipolar Junction Transistor
Normally Emitter layer is heavily doped, Base layer is lightly doped and Collector layer has Moderate doping.
npn pnp
n p n E
B
C p n p E
B
C
Cross Section Cross Section
B
C
E
Schematic Symbol
B
C
E
Schematic Symbol
17 September 2019 7
transistor currents
N
P
E
B
Collector Base Junction JC
Emitter Base Junction JE
E Emitter
B Base
17 September 2019 8
Number of P-N junctions and equivalent circuit
N
P
E
B P
N
B
C
E Emitter
C Collector
B Base
17 September 2019 9
An unbiased Transistor – Depletion region
• For an unbiased transistor no external power supplies are
connected to it
P
Junction JEB
Emitter collector
N
Base Junction JCB
N
Depletion region
Depletion region
-
-
-
-
-
+
+
+
+
+
-
-
-
-
-
+
+
+
+
+
-
-
-
-
-
-
-
-
-
-
17 September 2019 10
Transistor biasing in the active region
Sr.
No.
Region of
operation
Base emitter
junction
Collector base
junction
application
1 Cutoff region Reverse
biased
Reverse
biased
transistor is OFF
2 Saturation
region
Forward
biased
Forward
biased
transistor is ON
3 Active
region
Forward
biased
Reverse
biased
Amplifier
17 September 2019 11
Transistor operation in the active region P-N-P
P
Junction JEB
Emitter collector
N
Base
Junction JCB
VEE
RE
+ -
RC
VCC
-
holes emitted holes collected
Conventional current
conventional current
+
P P N
IE = IC + IB 17 September 2019 12
Transistor configuration
• Depending on which terminal is made common to input and
output port there are three possible configurations of the
transistor. They are as follows:
• Common base configuration
• Common emitter configuration
• Common collector configuration
17 September 2019 13
Transistor operation in the active region N-P-N common base configuration
P
Junction JEB
Emitter collector
N
Base
Junction JCB
N
VEE
RE
+ -
RC
VCC
+ -
Electron emitted Electron collected
Emitter electron current
Direction Conventional Current IC (INJ)
Direction Conventional Current IB
Direction Conventional Current IE
(injected collector current)
17 September 2019 14
Transistor operation in the active region N-P-N common base configuration
P
JEB
Emitter collector
N
Base
JCB
N
Depletion region
Depletion region
-
-
-
-
-
+
+
+
+
+
-
-
-
-
-
+
+
+
+
+
-
-
-
-
-
-
-
-
-
-
RC
VCC
+ -
IC=ICBO
ICBO
Is a collector to base leakage current With open emitter
ICBO is a reverse saturation Current flowing due to the Minority carriers between Collector and base when the Emitter is open. ICBO flows due to the reverse Biased collector base junction. ICBO is neglected as compared to IC
17 September 2019 15
Current relations in CB configuration
• Current amplification factor ( αdc)
• the current amplification factor is the ratio of collector current
due to the injection of total emitter current
IC = IC(INJ) + ICBO
αdc = IC(INJ) / IE
IC(INJ) = αdc IE
But ICBO is negligibly small
Therefore the current amplification factor
IC = αdcIE + ICBO
IC = αdcIE
αdc= IC / IE 17 September 2019 16
Characteristics of a transistor in CB configuration
Input characteristics
N P
JC JE
N
B
C E
+ -
B
C E
+ -
VEE
VEE
RE
RE
IE
IE
VBE
-
+
VBE
-
+ VCB =8V
+
-
+
-
VBE
IE
VCB =8V
VCB 4V
VCB 8V
ΔVBE
ΔIE
Input resistance Ri = ΔVBE / ΔIE
As the change in emitter current is very large for a Small change in input voltage, the input resistance Ri is small
17 September 2019 17
Characteristics of a transistor in CB configuration
“Early effect” or “base width modulation”.
Base P
JE
Emitter collector
Emitter N
JC
Collector N
Wider Depletion Region for larger values of VCB
-
-
-
-
-
+
+
+
+
+
Total base width
zero effective base width At larger values of VCB
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
VCB increases extremely
For extremely large VCB the effective base width may be reduced to zero, causing voltage breakdown of a transistor.
This phenomenon is known as punch through
-
-
-
-
-
-
-
-
-
-
17 September 2019 18
Characteristics of a transistor in CB configuration
Output characteristics
N P
JC JE
N
B
C E
+ -
B
C E
+ -
VEE
VEE
RE
RE
Constant IE=3mA
Constant IE=3mA
VEB
-
+
VCB +
RC
+ -
VCC
IC
+ -
VCC
RC
IC
VCB +
-
VCB
IC (mA)
0 5 10 -1
IE=0 IC=ICBO
Cutoff region Both the junctions are reverse biased
IE=1 mA 1
2 IE=2 mA
3 IE=3 mA
Active region (high output dynamic resistance)
saturation region Both the junctions are forward biased
17 September 2019 19
Characteristics of a transistor in CB configuration
Transfer characteristics
0 1 2 3 4
4 3 2 1
IE (mA)
IC (mA) VCB constant
Slope = ΔIC / ΔIE = αdc
α dc = ΔIC / ΔIE
17 September 2019 20
Characteristics of a transistor in CE configuration
• It is a graph of input current (IB) versus input voltage (VBE) at a constant output voltage (VCE).
N
N
P
C
E
B JC
JE
+
-
-
+
RB
IC
IB
IE
VCE constant
VBE
VBB
VCC
N-P-N Transistor
VBE
IB (μA) VCE = 4V 10V
0 0.7 1 2
The value of dynamic input resistance “Ri” is low for CE
ΔIB
ΔVBE Ri=ΔVBE/ΔIB
VCE Constant
Input characteristics
17 September 2019 21
Characteristics of a transistor in CE configuration
• It is a graph of output current (Ic)
versus output voltage (VCE) at a
constant input current (IB)
E
C
N-P-N Transistor
-
+
RE
B
+
-
RB
IC
IE
VCC VCE VBE
VBB
VCE
IB = 0
4 3 2 1
IC (mA)
1 2 3 4
Cutoff region
IB = 2μA
IB = 4μA
IB = 3μA
IB = 4μA
Saturation region
Active region
βdc = IC /IB
Output characteristics
17 September 2019 22
Characteristics of a transistor in CE configuration
Transfer characteristics
0 1 2 3 4
4 3 2 1
IB (μA)
IC (mA) VCE constant
Slope = ΔIC / ΔIB = βac
β ac = ΔIC / ΔIB
β dc = IC / IB VCE constant 17 September 2019 23
Comparison of configurations
Sr. No. Parameter CB CE CC
1 Common terminal
between input and output
Base
Emitter
Collector
Conduction Angle 0 o 180 o 0 o
2 Input current IE IB IB
3 Output current IC IC IE
4 Current gain αDC = IC/IE
Less than one
βDC = IC/IB
High
γ = IE/IB
HIGH
5 Input Voltage Veb Vbe Vbc
6 Output voltage Vcb Vce Vec
7 Current gain Less than unity High High
8 Input resistance Very low (20Ω) Low (1KΩ) High(500kΩ)
9 Output resistance Very high (1M) High(40kΩ) Low (50Ω)
10 Application As
preamplifier
Audio
amplifier
Impedance
matching
11. Voltage gain
Medium Large Less than 1 17 September 2019 24
Transistor Biasing
• What is meant by dc biasing of a transistor ?
• Depending on the application, a transistor is to be operated in
any of the three regions of operation namely cutoff, active and
saturation region.
• To operate the transistor in these regions the two junctions of a
transistor should be forward or reverse bias
17 September 2019 25
DC Load Line
IC = [-1/RC] VCE + VCC/RC
• and substituting IC = 0 in above equation
• VCE = VCC or point “B”
VCE
IB = 0
A 3 2 1
IC (mA)
1 2 3 4
IB = 2μA
IB = 3μA
IB = 4μA
E
C
N-P-N Transistor
-
+
RC IC
VCC VCE
IC (MAX)
VCE=VCC
B
DC load line
17 September 2019 26
17 September 2019 27
Typical Junction Voltages Voltage Silicon Transistor Germanium Transistor
VBE (Cut-off) 0 -0.1V
VBE (Cut-in)
0.5v 0.1V
VBE (Active)
0.7V 0.2V
VBE (Saturation)
0.8V 0.3V
VCE (Saturation)
0.2V 0.1V
17 September 2019 28
Biasing circuits
To avoid a shift of Q-point, bias-stabilization is
necessary. Various biasing ckts can be used for this
purpose.
• Fixed bias
• Collector-to-base bias
• Self Biased or Voltage divider bias
• Fixed bias with emitter resistor
• Emitter bias
17 September 2019 29
RC
RE CE R2
R1
+VCC
C1
C2 VO
Vi Signal to be Amplified RL
Amplified signal output Signal
R1 & R2 are Biasing Resistor
C1 & C2 are Coupling
Capacitors
Bypass Capacitor
Single Stage RC Coupled CE Amplifier
17 September 2019 30
BJT Switch
• When operated in
saturation, the BJT
acts as a closed
switch.
• When operated in
cutoff, the BJT acts as
an open switch.
17 September 2019 31
MOSFET
17 September 2019 32
FIELD-EFFECT TRANSISTORS ( FET)
• FETs are the uni polar devices because, unlike BJTs
that use both electron and hole current, they operate
only with one type of charge carrier.
• The two main types of FET’s are -
Junction Field Fffect Transistor (JFET) and
Metal Oxide Semiconductor Field Effect Transistor
(MOSFET)
17 September 2019 33
Current Controlled & Voltage Controlled Devices
17 September 2019 34
Field Effect Transistors - Classification
17 September 2019 35
MOSFET (IGFET)
• The MOSFET (metal oxide semiconductor field effect transistor) is the category of FET.
• The MOSFET differs from the JFET in that it has no PN junction structure; instead, the gate of the MOSFET is insulated from the channel by a silicon dioxide (Sio2) layer.
• Two basic types of MOSFETS are :
Depletion ( D ) MOSFET and
Enhancement ( E ) MOSFET
• Because of the insulated gate, these devices are also called as IGFET.
17 September 2019 36
ENHANCEMENT MOSFET ( E-MOSFET)
MOSFET was invented by Atalla & Dawon at Bell Labs in 1959 17 September 2019 37
Linear & Saturation Regions
17 September 2019 38
17 September 2019 39
Transfer & Drain Characteristics
17 September 2019 40
BJT MOSFET It is a current controlled device. It is a voltage controlled device.
It is a bipolar device (Current flows due
to both majority & minority carriers).
It is a unipolar device (Current flows
due to only majority carriers).
Thermal Runaway can damage the BJT Thermal Runaway does not take place
Input resistance (Ri) is very low. Output resistance (Ro) is very high.
Transfer characteristics are linear in
nature.
Transfer characteristics are non-linear in
nature.
BJT is More sensitive than MOSFET MOSFET is less Sensitive
AC Voltage Gain is HIGH AC Voltage Gain is Less
Bigger in size. Smaller in size.
Regions of operation: Saturation – ON
Switch , Cut off – OFF Switch
Active – Amplifier
Regions of operation: Ohmic – ON
Switch ,Saturation – Amplifier ,
Cut off – OFF Switch
It is more noisy. It is less noisy.
Switching speed is less. Switching speed is high.
Symbol Symbol
17 September 2019 41
17 September 2019 42
Operational Amplifier
An operational amplifier (often op-amp or opamp) is a DC coupled high-gain electronic voltage amplifier with a differential input and usually, a single-ended output
17 September 2019 43
• Op-amp is basically a multistage amplifier which is uses a number of amplifier stages interconnected to each other in a complicated manner.
• The amplifier which could be configured to perform a variety of operations such as amplification, addition, subtraction, differentiation and integration.
• Hence the name is operational amplifier (OP-AMP)
• The integrated Op-amp offers all the advantages of monolithic integrated circuits such as small size, high reliability, reduced cost, less power consumption.
• IC 741 is extremely popular and was used in a variety of applications.
17 September 2019 44
Pin configuration of OP-AMP IC 741
17 September 2019 45
Symbol and terminal
741
2
3
4
7
6 -
+
+VCC positive supply voltage
-VEE negative supply voltage
Output
Inverting input
Non-Inverting input
The Operational Amplifier (op amp) was invented in the 40's. Bell Labs filed a patent in 1941 and many consider the first practical op amp to be the vacuum tube K2-W invented in 1952 by George Philbrick. 17 September 2019 46
Op-amp symbols and packages.
Thomas L. Floyd
Electronic Devices, 6e and Electronic
Devices: Electron Flow Version, 4e
17 September 2019 47
Manufactures of OP-AMP IC 741
• The manufactures of Op-amp ICs are companies like Fairchild, National semiconductor, Motorola, Texas Instruments and signetics.
• The identifying initials for some other companies are as follows:
1. National semiconductors : LM 741
2. Motorola : MC 741
3. RCA : CA 741
4. Texas instruments : SN 52741
5. Signetics : N 5741 17 September 2019 48
Ideal differential amplifier
• An ideal differential amplifier is expected to amplify the differential signal present between its two input signal.
• It is also the basic stage of an integrated Op-amp with differential input.
V2 V1
Vd
Vo = V1 – V2 + +
- -
Ideal
Differential
Amplifier
17 September 2019 49
Ideal
Differential
Amplifier
V2 V1
Vd
Vo = V1 – V2 + +
- -
Differential gain - • Vo = Ad ( V1 – V2 ) Where Ad is called as the differential gain. • The differential gain can be defined as the gain with which the
differential amplifier amplifies the differential signal. Vo = Ad Vd as Vd = V1 – V2 Gain Ad = Vo / Vd Ad (dB) =10 log10 [ Vo / Vd ]
17 September 2019 50
Ideal
Differential
Amplifier
V2 V1
Vd
Vo = V1 – V2 + +
- -
Common mode signal
• A common signal to both the input terminals ( i.e. V1=V2=V) is called as common mode signal.
• The output voltage produced by an ideal differential amplifier is zero for the common mode signal.
17 September 2019 51
Block diagram of a typical OP-AMP
Input
Stage
Intermediate
stage
Level
shifting
stage
Output
Stage
Non-inverting
input
Inverting
input
+
-
Output
Dual input
Balanced
Output
Differential
amplifier
Dual input
unbalanced
Output
Differential
amplifier
Such as
Emitter follower
Using constant
Current source
Complementary
Symmetry
Push-pull
amplifier
17 September 2019 52
17 September 2019 53
Input and output signals 1800 phase shift when the input signal is
applied to the inverting (-) terminal
741
2
3
4
7
6 -
+
+VCC
-VEE
Vo
Inverting input input
Inverted Output signal
17 September 2019 54
Input and output signals 00 phase shift when the input signal is
applied to the Non-inverting (+) terminal
741
2
3
4
7
6 -
+
+VCC
-VEE
Vo
Non-Inverting
input input
Non-Inverted Output signal
17 September 2019 55
Ideal
Differential
Amplifier
V2 V1
Vd
Vo = V1 – V2 + +
- -
Common mode rejection ratio (CMRR)
• Common mode rejection ration (CMRR) is the ability of a differential amplifier to reject the common mode signal successfully.
• CMRR is defined as the ratio of differential gain Ad and common mode gain Ac. It is denoted by letter “ρ”
• CMRR = ρ = Ad / Ac
• Ideally CMRR should be infinite and practically it should be as high as possible.
17 September 2019 56
Equivalent circuit of an OP-AMP
-
+
+ VCC
-VEE
Output
Inverting input
Non-Inverting input
RL
Ro
AVVd
+
- Vo
Ri
-
+ Vd
17 September 2019 57
The ideal OP-AMP
-
+
Output
V2
V1
Ro
AVVd
+
-
Ri Vd= 0 Zero differential Input voltage
Ri
8
Ro 0
AV 8
IB2= 0
IB1= 0
Vo = AVVD
Important characteristics of Op-Amp
1. Infinite voltage gain ( )
the open loop gain of an ideal OP-AMP is denoted by Av. It is the
differential voltage gain and its value for an ideal OP-AMP is infinite.
AV
8
Vo = AVVD 17 September 2019 58
The ideal OP-AMP
-
+
Output
V2
V1
Ro
AVVd
+
-
Ri Vd= 0 Zero differential Input voltage
Ri 8
Ro 0
AV 8
IB2= 0
IB1= 0
Vo = AVVD
2. Infinite input resistance (Ri ∞)
the input resistance Ri of an ideal OP-amp is infinite. Due to this,
the current flowing in each input terminal will be zero.
due to infinite input resistance, almost any source can drive it and
there is no loading of the source.
IB1= 0 IB2= 0
17 September 2019 59
The ideal OP-AMP
-
+
Output
V2
V1
Ro
AVVd
+
-
Ri Vd= 0 Zero differential Input voltage
Ri 8
Ro 0
AV 8
IB2= 0
IB1= 0
Vo = AVVD
3. Zero output resistance ( = )
the output resistance Ro of an ideal OP-amp is zero. Due to this,
the ideal Op-amp can handle infinite number of other devices.
RO 0
17 September 2019 60
The ideal OP-AMP
-
+
Output
V2
V1
Ro
AVVd
+
-
Ri Vd= 0 Zero differential Input voltage
Ri 8
Ro 0
AV 8
IB2= 0
IB1= 0
Vo = AVVD
4. Zero offset voltage
in practical Op-amps a small output voltage is present even though
both the inputs V1 ad V2 are having a zero value.
This voltage is called as the offset voltage.
for ideal Op-amp the offset voltage is zero.
That means output voltage is zero when input voltage is zero. 17 September 2019 61
The ideal OP-AMP
-
+
Output
V2
V1
Ro
AVVD
+
-
Ri Vd= 0 Zero differential Input voltage
Ri 8
Ro 0
AV 8
IB2= 0
IB1= 0
Vo = AVVD
5. Infinite Bandwidth
Bandwidth of an amplifier is the range of frequencies over which all
the signal frequencies are amplified almost equally.
The bandwidth of an ideal Op-amp is infinite. So it can amplify any
frequency from zero to infinite hertz.
Thus the gain of an ideal amplifier is constant from zero to infinite hertz. 17 September 2019 62
The ideal OP-AMP
-
+
Output
V2
V1
Ro
AVVD
+
-
Ri Vd= 0 Zero differential Input voltage
Ri 8
Ro 0
AV 8
IB2= 0
IB1= 0
Vo = AVVD
6. Infinite CMRR
for an Op-amp, the common mode rejection ratio (CMRR) id defined
as the ratio of differential gain to common mode gain.
CMRR is infinite for the ideal Op-amp.
Thus the output voltage corresponding to the common mode noise is zero.
17 September 2019 63
The ideal OP-AMP
-
+
Output
V2
V1
Ro
AVVD
+
-
Ri Vd= 0 Zero differential Input voltage
Ri 8
Ro 0
AV 8
IB2= 0
IB1= 0
Vo = AVVD
7. Infinite slew rate
the slew rate of an ideal Op-amp is infinite so that the output voltage
changes occur simultaneously with the input voltage changes.
17 September 2019 64
The ideal OP-AMP
-
+
Output
V2
V1
Ro
AVVD
+
-
Ri Vd= 0 Zero differential Input voltage
Ri 8
Ro 0
AV 8
IB2= 0
IB1= 0
Vo = AVVD
8. Zero power supply rejection ratio (PSRR).
PSSR is a parameter which specifies the degree of the dependence
of the Op-amp output on the changes in power supply output. For an
ideal Op-amp, PSRR = 0. that means the output voltage does not
Change due to fluctuation in supply voltage 17 September 2019 65
Important characteristics of OP-AMP IC 741
Sr. No. Characteristics Value for IC 741 Ideal value
1 Input resistance Ri 2 MΩ
2 Output resistance Ro 75 Ω 0
3 Voltage gain Av 2 X 105
4 Bandwidth BW 1 MHz
5 CMRR 90 dB
6 Slew rate S 0.5 V/μS
7 Input offset voltage 2 mV 0
8 PSRR 150 μV/V 0
9 Input bias current 50 nA 0
10 Input offset current 6 nA 0
8
8
8
8
8
17 September 2019 66
Open loop configuration of OP-AMP
• The meaning of open loop operation is that there is absolutely no feedback present from the output to input.
Vd
Vo = Av Vd + +
- -
Op amp
-
+ V1
V2
0 b a
+V(SAT)
-V(SAT)
Vo = Av Vd
Vd
17 September 2019 67
Open loop configuration of OP-AMP
17 September 2019 68
Why Op-amp not used as an amplifier in the open loop configuration ?
• Due to very large open loop gain, distortion is introduced in the amplified output signal.
• The open loop gain does not remain constant, it varies with change in temperature and power supply.
• The bandwidth of an Op amp in open loop mode is very very small – almost zero
• For this reason the Op-amp is not used in practice as an amplifier.
• However the Op-amp in open loop configuration is used in application such as comparator.
17 September 2019 69
Close loop configuration of OP-AMP
• In the closed loop configuration some kind of “feedback” is introduced in the circuit.
• A part of output is returned back or fed back to the input.
• Types of feedback
Positive feedback or Regenerative feedback
Negative feedback or Degenerative feedback.
17 September 2019 70
Positive feedback or regenerative feedback
• If the feedback signal and the original input signal are in phase with each other then it is called as the positive feedback.
• Positive feedback is used in the application such as “Oscillators” and Schmitt triggers or regenerative comparators.
17 September 2019 71
Negative feedback or Degenerative feedback
• If the signal is fed back to the input and the original input signal are 1800 out of phase, then it is called as the negative feedback.
• In the application of Op-amp as an amplifier, the negative feedback is used.
17 September 2019 72
Negative feedback or Degenerative feedback
• In the amplifier circuits using Op-amp, a feedback resistor RF is connected between the output and inverting terminal as shown in figure to introduced a negative feedback.
• As the voltages V2 and VO are 1800 out of phase, a fraction of output voltage fed back to the input via RF will be 1800 out of phase with the input.
OP-AMP
2
3
6 -
+
V2
V1
RF
input
Output
Feedback resistor
Vo
17 September 2019 73
Advantages of Negative feedback
• Negative feedback is used in the amplifier circuits as they provide the following improvements in the operation of an amplifier:
• It stabilizes the gain.
• Reduces the distortion.
• Increases the bandwidth.
• Changes the values of input and output resistances.
• Reduces the effects of variation in temperature and supply voltage on the output of the Op-amp.
17 September 2019 74
Virtual short
-
+
Output
V2
V1
Ri Vd
Ri 8
I = 0
Vo = AVVD
-VEE
+VCC
The input impedance Ri of an Op-amp is ideally infinite. Hence current “I” flowing from one input terminal to the other will
be zero. Thus the voltage drop across Ri will be zero and both the input terminals will be at same potential, in other words they are virtually shorted to each other. 17 September 2019 75
OP-AMP
-
+
VS
V1
RF
Vo
R1 +
-
V2
Vd
IB2 = 0
+ -
- +
AV =
8
input
t
t 0
0
VS
VO
Expression for the closed loop voltage gain (AVF)
AVF = - RF / R1
The negative sign indicates that there is a phase shift of 1800 Between the input and output voltages.
I
The Inverting Amplifier
17 September 2019 76
OP-AMP
-
+
VS
V1
RF
Vo
R1
+
-
V2
I2 = 0
+ - - +
AV =
8
input
t
t 0
0
VS
VO
I1 = 0
As input impedance of ideal Op-amp is infinite, the current entering into both the input terminals of
Op-amp will have zero values. (I1 = I2 = 0 )
The Non-Inverting Amplifier
17 September 2019 77
The Voltage follower (unity gain buffer)
OP-AMP
-
+
VS
V1
RF = 0
Vo
+
-
V2
I2 = 0
+ - - +
AV =
8
I1 = 0
When R1 is infinite and RF = 0 the non-inverting amplifier gets converted into a voltage follower or unity gain.
R1 =
8
17 September 2019 78
Conclusion
• Read the Instruction Manuals of equipment i.e. Car, Washing m/c, Microwave oven, Cell phone, Laptop etc.
• BJT is used rarely.
• MOSFET is matured technology & used everywhere.
• MOSFET ckts have low dissipations, high swing & integration.
• Device / Ckt / Chip / Application designers are well respected. Less effect of recession.
• Classrooms may diminish; Hands on has only meaning.
• Knowledge of E&TC is must for every branch.
• Opamp is hot topic forever !
17 September 2019 79
Recommended