Download - Ppt of Analog
CENT-112 Fundamentals of Electricity and Electronics1
Tubes, Transistors and Amplifiers
CENT-112 Fundamentals of Electricity and Electronics2
InterestIn 1947, Bardeen & Brattain at Bell Laboratories created the first amplifier! Shockley (boss), came near to canceling the project. The three shared a Nobel Prize. Bardeen and Brattain continued in research (and Bardeen later won another Nobel). Shockley quit to start a semiconductor company in Palo Alto. It folded, but its staff went on to invent the integrated circuit (the "chip") & to found the Intel Corporation.
CENT-112 Fundamentals of Electricity and Electronics3
(+) Plate
(-) Shield
Control Grid
(-) Cathode
Heater
Inert Gas
Tetrode TubeControl Grid: Controls amplification rate & electron flow with bias voltage.
Shield: Screen grid- increases electron speed cathode to + plate.
Heater: Heats gas to gas amplification state.
Inert Gas: Mercury or Argon gas.
CENT-112 Fundamentals of Electricity and Electronics4
Cathode Ray Tube (CRT)
(+) Anode(-) Cathode
3 Electron Beams (Red, Green, Blue)
GridsPhosphor
CoatedScreen
ConductiveCoating
The cathode is a heated filament (like light bulb filament) in a vacuum inside a glass tube. The ray is a stream of electrons that naturally pour off a heated cathode into the vacuum. The + anode attracts the electrons pouring off the cathode. In a TV's CRT, the stream of electrons is focused by a focusing anode into a tight beam and then accelerated by an accelerating anode. This tight, high-speed beam of electrons flies through the vacuum in the tube and hits the flat screen at the other end of the tube. This screen is coated with phosphor, which glows when struck by the beam.
CENT-112 Fundamentals of Electricity and Electronics5
Bipolar Transistors
•History–Created in 1948 in the AT&T Bell Laboratories.–Scientists were performing doping experiments on semiconductor material (diodes) and developed a semiconductor device having three (3) PN junctions.
CENT-112 Fundamentals of Electricity and Electronics6
• NPN / PNP Block Diagrams
Bipolar Transistor Construction
Emitter
Emitter
N P N
P N P
Collector
Base
Base
Collector
CENT-112 Fundamentals of Electricity and Electronics7
• For any transistor to conduct, two things must occur.The emitter - base PN junction
must be forward biased. The base - collector PN junction
must be reverse biased.
Bipolar Transistor Theory
CENT-112 Fundamentals of Electricity and Electronics8
+ N P NEmitter
Base +
-
FB RB
Bipolar Transistor Biasing (NPN)
Collector
CENT-112 Fundamentals of Electricity and Electronics9
P N PEmitter Collector
Base
+
-
-
FB RB
Bipolar Transistor Biasing (PNP)
CENT-112 Fundamentals of Electricity and Electronics10
Bipolar Transistor Operation (PNP)•90% of the current carriers pass through the reverse biased base - collector PN junction and enter the collector of the transistor.
•10% of the current carriers exit transistor through the base.
•The opposite is true for a NPN transistor.
CENT-112 Fundamentals of Electricity and Electronics11
• The transistor below is biased such that there is a degree of forward bias on the base - emitter PN junction.
• Any input received will change the magnitude of forward bias & the amount of current flow through the transistor.
Amplifier Operation
RB
RC
Q1
+
0
+VCC
Input Signal
+
0
Output Signal
CENT-112 Fundamentals of Electricity and Electronics12
Amplifier Electric Switch Operation•When the input signal is large enough, the transistor can be driven into saturation & cutoff which will make the transistor act as an electronic switch.•Saturation - The region of transistor operation where a further increase in the input signal causes no further increase in the output signal.•Cutoff - Region of transistor operation where the input signal is reduced to a point where minimum transistor biasing cannot be maintained => the transistor is no longer biased to conduct. (no current flows)
CENT-112 Fundamentals of Electricity and Electronics13
Amplifier Electric Switch Operation–Transistor Q-point
•Quiescent point : region of transistor operation where the biasing on the transistor causes operation / output with no input signal applied.
–The biasing on the transistor determines the amount of time an output signal is developed.
–Transistor Characteristic Curve•This curve displays all values of IC and VCE for a given circuit. It is curve is based on the level of DC biasing that is provided to the transistor prior to the application of an input signal.
–The values of the circuit resistors, and VCC will determine the location of the Q-point.
CENT-112 Fundamentals of Electricity and Electronics14
Transistor Characteristic Curve
IC
VCE
Q-Point
IB
0 uA
10 uA
20 uA
30 uA
40 uA
50 uA
60 uA
70 uA80 uA90 uA
Saturation
Cutoff
CENT-112 Fundamentals of Electricity and Electronics15
• When troubleshooting transistors, do the following:
– Remove the transistor from the circuit, if possible.
– Use a transistor tester, if available, or use a digital multimeter set for resistance on the diode scale.
– Test each PN junction separately. ( A “front to back” ratio of at least 10:1 indicates a good transistor).
Transistor Maintenance
CENT-112 Fundamentals of Electricity and Electronics16
Transistor Maintenance Chart
•This chart shows the readings for a good transistor.Test Lead
Connection( + / - )
NPNResistance Reading
(High / Low)
PNPResistance Reading
(High / Low)Base - Emitter LOW HIGH
Emitter - Base HIGH LOW
Base - Collector LOW HIGH
Collector - Base HIGH LOW
Emitter - Collector HIGH HIGH
Collector - Emitter HIGH HIGH
Transistor Maintenance
CENT-112 Fundamentals of Electricity and Electronics17
Questions
Q1. What is the 7 step troubleshooting method?
A1. Symptom recognition, symptom elaboration, list possible faulty functions, identify faulty function, identify faulty component, failure analysis, repair, retest.
Q2. What was the most difficult problem you ever troubleshot?
A2. Various
CENT-112 Fundamentals of Electricity and Electronics18
Bipolar Transistor Amplifiers
•Amplifier Classification–Amplifiers can be classified in three ways:
•Type (Construction / Connection)–Common Emitter
–Common Base
–Common Collector
•Bias (Amount of time during each half-cycle output is developed).
–Class A, Class B, Class AB, Class C
•Operation–Amplifier
–Electronic Switch
CENT-112 Fundamentals of Electricity and Electronics19
Common Emitter Schematic
RB
RC
Q1
+
0
+VCC
Input Signal
+
0
Output Signal
Output Signal Flow Path
Input Signal Flow Path
CENT-112 Fundamentals of Electricity and Electronics20
• DC Kirchoff Voltage Law Equations and Paths
Kirchoff Voltage Law
RB
RC
Q1
+VCC
Base - Emitter Circuit
ICRC + VCE - VCC = 0
IBRB + VBE - VCC = 0
Collector - Emitter Circuit
CENT-112 Fundamentals of Electricity and Electronics21
Common Emitter Operation
Positive Going Signal
Negative Going Signal
Output Signal
Input Signal
+
+
0
0 Base becomes more (+) WRT Emitter FB IC VRC
VC VOUT ( Less + )
Base becomes less (+) WRT Emitter FB IC VRC
VC
VOUT ( More + )
RC
RB
Q1
CENT-112 Fundamentals of Electricity and Electronics22
Common Base Schematic
+
0
+
0+VCC
RBRCRE
Q1
CC
Input Signal Flow Path
Output Signal Flow Path
CENT-112 Fundamentals of Electricity and Electronics23
• DC Kirchoff Voltage Law Equations and Paths
Kirchoff Voltage Law
+VCC
RBRCRE
Q1
CC
Base - Emitter CircuitIBRB + VBE + IERE - VCC = 0
Collector - Emitter CircuitICRC + VCE + IERE - VCC = 0
CENT-112 Fundamentals of Electricity and Electronics24
Common Base Operation
Positive Going Signal
Negative Going Signal
+VCC
RBRCRE
Q1
CC
Base becomes more (+) WRT Emitter FB IC VRC
VC
VOUT ( More + )
Base becomes less (+) WRT Emitter FB IC VRC
VC VOUT ( Less + )Input
Signal
0Output Signal
+
0
CENT-112 Fundamentals of Electricity and Electronics25
Common Collector Schematic
RB
RE
Q1
+
0
+VCC
Input Signal +
0
Output Signal
Output Signal Flow Path
Input Signal Flow Path
CENT-112 Fundamentals of Electricity and Electronics26
• DC Kirchoff Voltage Law Equations and Paths
Kirchoff Voltage Law
RB
RE
Q1
+VCC
Base - Emitter CircuitIBRB + VBE + IERE - VCC = 0
Collector - Emitter CircuitICRC + VCE + IERE - VCC = 0
CENT-112 Fundamentals of Electricity and Electronics27
Common Collector Operation
Positive Going Signal
Negative Going Signal
RB
RE
Q1
+VCC
Base becomes more (+) WRT Emitter FB IE VRE
VE
VOUT ( More + )
Base becomes less (+) WRT Emitter FB IE VRE
VE VOUT ( Less + )Input
Signal
0 0
+ +
Output Signal
CENT-112 Fundamentals of Electricity and Electronics28
AZAZA VOPINI & House of BEC
Av = Voltage Gain
Zo = Output Impedance
Ap = Power gain
Zin = Input Impedance
Ai = Current Gain
Av = Voltage Gain
Zo = Output Impedance
Ap = Power gain
Zin = Input Impedance
Ai = Current Gain
Common Common Common
B E C
Common Common Common
B E C
CENT-112 Fundamentals of Electricity and Electronics29
Transistor Bias Stabilization
•Used to compensate for temperature effects which affects semiconductor operation. As temperature increases, free electrons gain energy and leave their lattice structures which causes current to increase.
CENT-112 Fundamentals of Electricity and Electronics30
Types of Bias Stabilization
•Self Bias: A portion of the output is fed back to the input 180o out of phase. This negative feedback will reduce overall amplifier gain.
•Fixed Bias: Uses resistor in parallel with Transistor emitter-base junction.
•Combination Bias: This form of bias stabilization uses a combination of the emitter resistor form and a voltage divider. It is designed to compensate for both temperature effects as well as minor fluctuations in supply (bias) voltage.
•Emitter Resister Bias: As temperature increases, current flow will increase. This will result in an increased voltage drop across the emitter resistor which opposes the potential on the emitter of the transistor.
CENT-112 Fundamentals of Electricity and Electronics31
Self Bias Schematic
RB
RC
Q1
+VCC
+
=
Initial Input
Self Bias Feedback
Resulting Input
+
+
+
+
o o
o
o
VOUT
CENT-112 Fundamentals of Electricity and Electronics32
Emitter Bias Schematic
RB
RC
Q1
+VCC
+
o
VOUT
RE
++
+
+
-
-Initial Input
+
o
CE
DC Component
AC Component
CENT-112 Fundamentals of Electricity and Electronics33
Combination Bias Schematic
RB1
RC
Q1
+VCC
+
o
VOUT
RE
++
+
+
-
-Initial Input
+
o
CE
DC Component
AC Component
RB2
CENT-112 Fundamentals of Electricity and Electronics34
Amplifier Frequency Response
•The range or band of input signal frequencies over which an amplifier operates with a constant gain.•Amplifier types and frequency response ranges.
•Audio Amplifier–15 Hz to 20 KHz
•Radio Frequency (RF) Amplifier–10 KHz to 100,000 MHz
•Video Amplifier (Wide Band Amplifier)–10 Hz to 6 MHz
CENT-112 Fundamentals of Electricity and Electronics35
Class ‘A’ Amplifier Curve
IC
VCE
IB
0 uA
10 uA
20 uA
30 uA
40 uA
50 uA
60 uA
70 uA80 uA90 uA
Saturation
Cutoff
Q-Point
CENT-112 Fundamentals of Electricity and Electronics36
Class ‘B’ Amplifier Curve
IC
VCE
IB
0 uA
10 uA
20 uA
30 uA
40 uA
50 uA
60 uA
70 uA
80 uA
90 uA
Saturation
Cutoff
Q-Point
CENT-112 Fundamentals of Electricity and Electronics37
Class ‘AB’ Amplifier Curve
IC
VCE
IB
0 uA
10 uA
20 uA
30 uA
40 uA
50 uA
60 uA
70 uA
80 uA
90 uA
Saturation
Cutoff
Q-Point
Can be used for guitar distortion.
CENT-112 Fundamentals of Electricity and Electronics38
Class ‘C’ Amplifier Curve
IC
VCE
IB
0 uA
10 uA
20 uA
30 uA
40 uA
50 uA
60 uA
70 uA
80 uA
90 uA
Saturation
CutoffQ-Point
CENT-112 Fundamentals of Electricity and Electronics39
Amplifier Coupling Methods
•Direct: The output of the first stage is directly connected to the input of the second stage. Best Frequency Response - No frequency sensitive components.
•Impedance (LC) Coupling: Similar to RC coupling but an inductor is used in place of the resistor. Not normally used in Audio Amplifiers.
•RC Coupling: Most common form of coupling used. Poor Frequency Response.
•Transformer Coupling: Most expensive form coupling used. Mainly used as the last stage or power output stage of a string of amplifiers.
CENT-112 Fundamentals of Electricity and Electronics40
Direct Coupling Schematic
RB1
RC1
Q1
+VCC1
RB2
RC2
Q2
+VCC2
CENT-112 Fundamentals of Electricity and Electronics41
RC Coupling Schematic
RB1
RC1
Q1
+VCC1
RB2
RC2
Q2
CC
+VCC2
CENT-112 Fundamentals of Electricity and Electronics42
Impedance Coupling Schematic
RB1
Q1
+VCC1
RB2
RC2
Q2
CC
+VCC2
CENT-112 Fundamentals of Electricity and Electronics43
Transformer Coupling Schematic
RB1
RC1
Q1
+VCC1
RB2
RC2
Q2
+VCC2
T1
CENT-112 Fundamentals of Electricity and Electronics44
Silicon Controlled Rectifiers
•Silicon Controlled Rectifiers (SCR)
–Construction
•Block Diagram
Anode Cathode
Gate
P PN N
Left Floating Region
CENT-112 Fundamentals of Electricity and Electronics45
OPAMP Voltage Regulators
Vin Vout
-+
CENT-112 Fundamentals of Electricity and Electronics46
SCR Schematic
Anode Cathode
Gate
CENT-112 Fundamentals of Electricity and Electronics47
SCR Bias
Anode
Gate
P PN NCathode
-
FB FB
RB
+
+
•When the SCR is forward biased and a gate signal is applied, the lightly doped gate region’s holes will fill with the free electrons forced in from the cathode.
CENT-112 Fundamentals of Electricity and Electronics48
SCR Operation
•Acts as an electronic switch•Essentially a rectifier diode which has a controllable “Turn - on” point. Can be switched approximately 25,000 times per second.•Once the SCR conducts, the gate signal can be removed. The difference in potential across the anode & cathode of the SCR will maintain current flow.•When the voltage across the SCR drops to a level below the “Minimum Holding” value, the PN junctions will reform and current flow through the SCR will stop.
CENT-112 Fundamentals of Electricity and Electronics49
SCR Phase Control
•The term Phase Control refers to a process where varying the timing of the gate signal to an SCR will vary the length of time that the SCR conducts.
–This will determine the amount of Voltage or Power delivered to a load.
CENT-112 Fundamentals of Electricity and Electronics50
Unijunction Transistors (UJT)
•Construction: Originally called “Double-based Diodes.”
–“P” Type material doped into the “N” type base material.–Placement of the Emitter into the Base determines the voltage level (%) at which the the UJT fires.
•This % is called the “Intrinsic Standoff Ratio ( ).”–Once constructed, the Intrinsic Standoff Ratio cannot be changed.
•The actual voltage value at which the UJT fires is determined by the amount of source voltage applied.
CENT-112 Fundamentals of Electricity and Electronics51
UJT Block Diagram
Emitter
Base 2
Base 1
P N Emitter
Base 2
Base 1
Equivalent Circuit
CENT-112 Fundamentals of Electricity and Electronics52
UJT Schematic Symbol
Emitter
Base 2
Base 1
CENT-112 Fundamentals of Electricity and Electronics53
UJT No Operation
•When VE is less than or equal to the voltage base one to emitter requirement (VE - B1), the UJT will not fire.
Emitter
Base 1
Base 2
P N
++
-
+
No Current Flow
Depletion Region
CENT-112 Fundamentals of Electricity and Electronics54
UJT Operation
Emitter
Base 1
Base 2
P N
++
-
+
UJT Fires
VE > VE-B1
•When VE is more than the voltage base one to emitter requirement (VE - B1), the UJT will fire.
CENT-112 Fundamentals of Electricity and Electronics55
UJT Sawtooth Generator
R1
C1
Q1
E
B1
B2
VBB
SW1VOUT
C1 Discharge
C1 Charge
CENT-112 Fundamentals of Electricity and Electronics56
UJT Relaxation Oscillator
R1
C1
Q1
VBB
SW1
VOUT1
C1 Discharge
C1 Charge
RB2
RB1
VOUT2
VOUT3
VOUT2
VOUT3
+
+
+
VOUT1
CENT-112 Fundamentals of Electricity and Electronics57
UJT Relaxation Oscillator
•The output of the Oscillator can be used for sweep generators, gating circuit for SCR’s, as well as timing pulses for counting and timing circuits.
CENT-112 Fundamentals of Electricity and Electronics58
Questions• Q3. What is the phase relationship between
input and output voltage in a common emitter circuit?
• A3. 180 degrees.
CENT-112 Fundamentals of Electricity and Electronics59
More Questions• Q4. What type of transistor bias uses both self
and fixed bias?
• A4. Combination bias.
• Q5. What is the frequency response range of an RF amplifier?
• A5. 10Khz – 100, 000 Mhz.
CENT-112 Fundamentals of Electricity and Electronics60
4 . Silicon Bilateral Switch (SBS)a . Construction
A2A1
G
P PN
J1 J2
A2A1
G
CENT-112 Fundamentals of Electricity and Electronics61
b . Schematic Symbol
Anode 2 Anode 1
A2 A1
Gate
CENT-112 Fundamentals of Electricity and Electronics62
c . Characteristic Curve
V A2-A1
I (mA)
Holding Current (IHO)
Reverse Breakover Voltage
Forward Breakover Voltage
Breakback Voltage
CENT-112 Fundamentals of Electricity and Electronics63
d . Characteristics1 . More vigorous switching characteristic. V to
almost zero.
2 . More temperature stable.
3 . More symmetrical wave form output.
4 . Popular in low voltage trigger control circuits.
e . Theory1 . Lower breakover voltages than Diac. (+/- 8V is
most popular).
2 . SBS has more pronounced “Negative Resistance” region.
3 . It’s decline in voltages is more drastic after it enters the conductive state.
CENT-112 Fundamentals of Electricity and Electronics64
f . Operation1 . As shown below, if a zener diode is placed in the
gate circuit between “G” and “A1”, the forward breakover voltage (+VBO) can be altered to approximately that of the zener voltage (VZ).
a . -VBO is unaffected.
SBS
A2 A1
G
CENT-112 Fundamentals of Electricity and Electronics65
2 . Characteristic Curve
V A2-A1
I (mA)
Holding Current (IHO)
Reverse Breakover Voltage
Forward Breakover Voltage
Breakback Voltage
CENT-112 Fundamentals of Electricity and Electronics66
5 Silicon Unilateral Switch (SUS)a Construction
P PN NAnode Cathode
Gate
CENT-112 Fundamentals of Electricity and Electronics67
b . Schematic Symbol
Anode Cathode
Gate
CENT-112 Fundamentals of Electricity and Electronics68
c Theory1 Similar to the four (4) layer diode except the +VBO can
be altered by using the gate terminal voltage.
d Operation
V A-C-V A-C
I
Forward Breakover Voltage
Reverse Breakdown Voltage
{ }Much greater than Forward Breakover Voltage
CENT-112 Fundamentals of Electricity and Electronics69
6 . Varactora . Construction
P N
CENT-112 Fundamentals of Electricity and Electronics70
b . Theory1 . For testing purposes, a front to back ratio of 10:1
is considered normal.
2 . The size of the depletion region in a varactor diode is directly proportional to the amount of bias applied.
a . As forward bias increases, capacitance (Depletion region) decreases.
b . As reverse bias increases, capacitance (Depletion region) increases.
3 . In the capacitance equation below, it is shown that only the distance between plates can be changed.
C = Akd
Where: A = Plate Areak = Constantd = Distance between plates
CENT-112 Fundamentals of Electricity and Electronics71
a . An increase in reverse bias increases the width of the gap (d) which reduces the capacitance of the PN junction and vice versa.
4 . Advantage: Allows DC voltage to be used to tune a circuit for simple remote control or automatic tuning function.
c . Operation1 . used to replace old style variable capacitor
tuning circuits.
2 . They are used in tuning circuits of more sophisticated communications equipment and in other circuits where variable capacitance is required.
CENT-112 Fundamentals of Electricity and Electronics72
3V 6V
20F 5F
P N P N
Depletion Region
CENT-112 Fundamentals of Electricity and Electronics73
A. Special Purpose Amplifiers1 . Differential Amplifier
a . Schematic Diagram
+ VCC
- VEE
RE
RB (1)
RC (1)RC (2)
RB (2)
Q1 Q2
VOUT
VIN (1) VIN (2)
CENT-112 Fundamentals of Electricity and Electronics74
b . Operation
+ VCC
- VEE
RE
RB (1)
RC (1)RC (2)
RB (2)
Q1 Q2
VOUT
VIN (1) VIN (2)
+ -
(+) / (-) ARE ASSIGNED BY WHICH VOLTMETER LEAD IS USED AS THE REFERENCE
+
0
+
0++ ++
+ +
- -
+
0
VOUT
CENT-112 Fundamentals of Electricity and Electronics75
2 . Operational Amplifiers (OPAMPS)a .Block Diagram (Basic)
DIFFERENTIAL AMPLIFIER
VOLTAGE AMPLIFIER
OUTPPUT AMPLIFIER
NON-INVERTING INPUT
INVERTING INPUT
+
-
+ vCC
- vEE
OUTPUT
CENT-112 Fundamentals of Electricity and Electronics76
b . Ideal OPAMP Characteristics1 . Infinite () Input Impedance
a Draws little or no current from source.2 . Zero Output Impedance3 . Infinite () Gain4 . Infinite () Frequency Response
a Constant gain over any range of input signal frequencies.
CENT-112 Fundamentals of Electricity and Electronics77
c . Types of OPAMPS1 . Linear (Output is Proportional to Input)
a . Inverting
+
-VOUT
VIN
RF
R1
+
0
+
0
+
-
CENT-112 Fundamentals of Electricity and Electronics78
b . Non - Inverting
+
-VOUT
VIN
RF
R1 +
0
+
0
+
-
CENT-112 Fundamentals of Electricity and Electronics79
c . Summing
+
-VOUT
VIN1
RF
R5
+0
+
0+
-
VIN4
+0
VIN3
+0
VIN2
+0
VIN1
VIN2
VIN3
VIN4
R1
R2
R3
R4
CENT-112 Fundamentals of Electricity and Electronics80
d . Difference
+
-VOUT
VIN1
RF
+0
+
0+
-
VIN4
+0
VIN3
+0
VIN2
+0
VIN1
VIN2
VIN3
VIN4
R1
R2
R3
R4
VIN5 0+ R5
VIN5
CENT-112 Fundamentals of Electricity and Electronics81
2 . Non - Linear (Output is not Proportional to Input)
a . Comparator
+
-VOUT
VIN
+
0
+
0
+
--
VREF
VREF ATTACHED TO EITHER + OR - TERMINALS
(EXAMPLE SHOWS OUTPUT WITH VREF CONNECTED TO THE NON-INVERTING TERMINAL.)
(WAVEFORM WOULD BE INVERTED IF VREF WAS ATTACHED TO THE INVERTING TERMINAL)
VIN VREF
VOUT
CENT-112 Fundamentals of Electricity and Electronics82
b . Differentiator
+
-VOUT
VIN
RF
R1
+
0
+
0
+
-
C1
CENT-112 Fundamentals of Electricity and Electronics83
c . Integrator
+
-VOUT
VIN
R1
+
0
+
0
+
-
C1