Atomic Numbers:Hydrogen - 1Helium - 2Carbon - 6

1.1 Atomic Structure:*Atom - smallest particle of an element that retains the characteristics of that element.*there are 109 elements*According to Neils Bohr, it is composed of (1) nucleus (middle protons and neutrons) and (2) surrounding electrons*Atomic Number = arrangement of elements in the periodic table / is the number of protons and electrons (if balanced)*Electrons that are near the nucleus have lower energy and are tightly bounded, due to the force of attraction between the electron and the proton*Discrete electron energies exist within atomic structures and each of them corresponds to a certain energy level.*Discrete distances = orbits and they are grouped into energy bands called shells*Number of Electrons in Each Shell: Ne = 2n2

*Valence shell (outermost shell) and valence electron (outermost electron)*Ionization: process of losing a valence electron (results to positive ion+) and gaining electrons (results to a negative ion-)

1.2 Insulators, Conductors, and Semiconductors:*Atom can be represented by a valence shell (outer shell) and core (other inner shells and nucleus)*Intrinsic - pure and no impurities*To compare conductivity, check (1) the valence electrons, (2) the core net charge, (3) distance of the valence shell.*Germanium is more unstable than Silicon.

Material Example # of Valence Electrons Conduction and Valence Band

Conductor copper (Cu), silver (Ag), gold (Au) and aluminum (Al)

1 - 3 Electrons No energy gap

Semiconductor Silicon (Si), Germanium (Ge) and Carbon (C), Gallium Arsenide (GaAs) and Indium Phosphide

(InP)

4 Electrons Wide energy gap

Insulator rubber, plastics, glass, mica and quartz 5-8 Electrons Very wide energy gap

Crystal = formed when semiconductor atoms bond together in symmetrical patternChemical Stability = 8 valence atomsCovalent bonds = a bond that hold the atoms together due to the sharing of valence electrons.

1.3 Current in Semiconductors:*Conduction band: after the valence band where free electrons go after having a sufficient amount of energy.*Free electrons = conduction electrons*hole = created when a valence electron jumps out of the valence band to become free electron*electron-hole pair: is created for every electron raised to the conduction band by external energy*recombination = occurs when a conduction-band electron loses energy and falls back into a hole in the valence band*Electron Current = after voltage is applied, the electrons are easily attracted toward the positive end. Negative to positive. *Hole Current = movement made by valence electrons in filling up nearby holes in the valence band. Positive to negative.*In copper's case, there is no hole-current!

Floyd (Chapter 1 - Introduction to Semi-Conductors)

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1.4 N-Type and P-Type Semiconductors:*Doping - adding impurities on the semiconductors, increasing the number of free electrons or holes to increase its conductivity.

Semiconductor Impurities Kind of Impurity Examples: Diagram: Carriers:

N-Type Pentavalent (5) Donor Atom Phosporus (P), Arsenic (As),Antimony (Sb) and Bismuth (Bi)

Majority: Conduction-band ElectronsMinority: Holes (not produced by the addition of impurities but by the silicon itself)

P-Type Trivalent (3) Acceptor Atom Boron (B), Indium (In) and Gallium (Ga)

Majority: Holes Minority: Conduction-band Electrons(not produced by the addition of impurities but by the silicon itself)

1.5 The Diode:PN Junction: the boundary between the p-type and the n-type semiconductors combined to assemble a diode.Diode: a device that conducts current in only one direction

Formation of the Depletion Region:1. Before they get combined together, the p-type and n-type are neutral on their own.2. As soon as they get combined, the holes in the p-type and the electrons in the n-type diffuse. The rightmost side of p-type near the junction creates a layer of negative charges (because it receives electrons) and the leftmost side of the n-type near the junction creates a layer of positive charges (because it loses electrons).3. These two layers

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3. These two layers

L form the depletion region. Depletion because the region near the pn junction is depleted of charge carriers (electrons and holes) due to the diffusion across the junction.4. The total negative charge in the depletion region repels further transfer of electrons. Hence, equilibrium is achieved.

Barrier Potential (in Volts) = amount of voltage required to move electrons through the electric field. (0.7V in Silicon and 0.3V in Germanium)

1.6 Biasing a Diode:*Bias: refers to the use of a DC voltage to establish certain operating conditions for an electronic device. Vbias = dc voltage used to produce forward biasRlimit = restricts the forward current to a value that will not damage the diode

Biases Definition Requirements What it does: Dynamic Resistance

1. Forward Bias

Allows current.

(1) Positive side of the voltage source to the p-region.(2) VBIAS > barrier potential

(1) Narrows the depletion region by reducing both the positive and negative ions.(2) Creates a VD = 0.7

Very small and can be neglected.

2. Reversed Bias

Prevents current.

(1) Positive side of the voltage source to the n-region.(2) VBIAS < breakdown voltage

(1) Widens the depletion region(2) Creates a very small current

Breakdown Voltage = reverse voltage bias that results to a strong reverse current. Typically 50V.Avalanche Effect = the strong reverse voltage imparts energy to the few electrons in the p-region that knocks out the valence electrons, which in turn knocks the others out. The strong impact speeds up the electron and allows them to pass through the depletion region onto the n-region.

1.7 Voltage-Current Characteristics of a Diode:

Forward Bias: Less than 0.7V More than 0.7V

Current Increases very minimally. Increases very rapidly.

Voltage Increases rapidly. Remains around 0.7V

Dynamic Resistance or AC Resistance Strong at this point. Weaker at this point.

Reverse Bias Before breakdown voltage After breakdown voltage

Current Small amounts of current (micro or nano amperes) Increases very rapidly.

Voltage Increases. Remains around VBR

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Voltage Increases. Remains around VBR

Dynamic Resistance or AC Resistance Strong at this point. Weaker at this point.

*As temperature increases, the forward and reverse current increases.

1.8 Diode Models

Diode Approximations Characteristics Figure

1. Ideal Diode Model *Diode = switch *no dynamic resistance or barrier potential*Forward Bias = On*Reverse Bias = Off

2. Practical Diode Model *Diode = switch with barrier potential*Forward bias = on + barrier voltage*Reversed bias = off (just like ideal)

3. Complete Diode Model *Diode = switch with barrier potential, small forward dynamic resistance and large internal reverse resistance.*Forward bias = on + barrier voltage + small dynamic resistance*Reversed bias = parallel large internal resistance

1.9 Testing a Diode*Multimeter - fast and simple way to check a diode*Good diode - very low resistance with forward bias and extremely high resistance in reverse bias*Defective short or resistive diode = will show zero or a low resistance for both.*Defective open diode = extremely high resistance for both.

Forward Bias Resistance Reverse Bias Resistance

Good Diode Very low resistance Extremely high resistance

Defective Open diode Extremely high resistance Extremely high resistance

Defective Shorted diode Very low resistance Very low resistance

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Diode - a single pn junction that conducts current in one direction while blocking current in the other direction

2.1 Half-Wave RectifiersDC Voltage Power supply - converts the standard AC voltage (120V or 220 V, 50Hz or 60Hz) into a constant DC voltage

Steps done by DC Voltage Power Supply

a. If secondary > primary = greater voltage / lesser currentb. If primary > secondary = lesser voltage / greater current

1. Transformer: AC input line voltage is stepped down to a lower AC voltage. It changes ac voltages based on the turns ratio between the primary and secondary.

2. Rectifier : convert AC voltage into pulsating dc voltage. Can be either half-wave or full wave rectifiers.3. Filter: eliminates fluctuation in the rectified voltage and produces a relatively smooth dc voltage4. Regulator: circuit that maintains a constant dc voltage for variations in the input line voltage or in the load.

Half-Wave Rectifier: a diode is connected to an ac source and to a load resistor (RL)

Average Value of the Half-Wave Output Voltage (VAVG or VDC): value measured on a DC voltmeter

Peak Inverse Voltage (PIV) = equals the peak value of the input voltage, and the diode must be capable of withstanding this amount of repetitive inverse voltage*maximum value of reverse voltage*diode should be rated at least 20% higher

Turns Ratio = number of turns in the secondary (NSEC) divided by the number of turns in the primary (NPRI).

*If n > 1, it is a step up type and n<1 is a step down type.

Floyd (Chapter 2 - Diode Applications)

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*If n > 1, it is a step up type and n<1 is a step down type.

2.2 Full-Wave Rectifiers*Full Wave Rectifiers - allow uni-directional (one way) current through the load during the entire 360 degrees of the input cycle (Half-wave rectifier - 180 degrees)

Average Value of a Full Wave Rectifier

Center-Tapped Full Wave Rectifier: two-diodes connected to the secondary of a center-tapped transform. Half of the total secondary voltage appears between the center tap and each end of the secondary winding. (Gitna 0, taas kalahating positve, baba kalahating negative.)

*diode drop = voltage across the diodePIV of Center-Tapped Full Wave Rectifier = voltage across the diode na pareverse! Voltage nung Vout minus voltage bago pumunta sa diode.

Bridge Full-Wave Rectifier - uses four diodes.

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2.3 Power Supply Filters and Regulators:- ideally eliminates the fluctuations in the output voltage of a half-wave or full-wave rectifier and produces a constant level dc voltage.- full wave rectifiers are easy to filter because the output frequency is twice and the capacitor discharges less

Ripple - small amount of fluctuation in the filter output voltage Ripple Voltage - variation in the capacitor voltage due to the charging and dischargingSmaller ripple means more effective filteringCapacitor Input Filter -

Steps:1. During the first positive first quarter-cycle of the input, the diode is forward biased, allowing the capacitor to charge to within 0.7V of the input peak.2. When voltage goes down from the peak, the capacitor retains its charge and the diode becomes reverse biased (since the capacitor's voltage is greater than the input.) The capacitor discharges.3. The capacitor again charges when voltage increases.

Skipped Ripple Factor to Percent Regulation

2 - 4 Diode Limiting and Clamping Circuits

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Skipped Diode Limiters

Diode Clampers - adds a dc level to an ac voltage.

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4-1 BJT Structure

*Bipolar - because it uses both holes and electrons as current carriers in the transistor structure.*Invented by Bell Laboratories by William Shockley, Walter Brattain and john Bardeen

*Bipolar Junction Transistor (BJT) - is constructed with three doped semiconductor regions separated by two pn junctions.

*Two broad uses of BJT - (1) Linear Amplifier (BJT - to boost or amplify an electric signal) and as an electronic switch. (FET)*Three regions of a BJT: (1) Emitter, (2) Base, (3) Collector*Two junctions of a BJT: (1) Emitter-Base, (2) Base-Collector*Two Types of BJT: (1) NPN (nakapasok na! outwards), (2) PNP (papasok pa lang. Inwards)

4.2 Basic BJT OperationForward-Reverse Bias - forward bias the base-emitter and reverse bias the base-collector. Used in amplifiers.

Current Directions:

4.3 BJT Characteristics and Parameters

*It varies due to collector current (1) and temperature (2).

Collector Characteristics:

Floyd (Chapter 4 - Bipolar Junction Transistors)

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Collector Characteristics:*For every given value of IB, there is a set of curves created with VCE as x-coordinate and IC as y coordinate.

Linear Operation (Active Region) - BE is forward biased and BC is reversed bias.Cut Off Region = Both CE and BC are reversed bias. IB = 0.Saturation Region - Both CE and BC are forward biased. Ic is large enough to short CE.

Maximum Transistor Ratings:*The product of VCE and IC must not exceed the maximum power dissipation. Both VCE and IC cannot be maximum at the same time.

Derating PD(max)

- naturally, power decreases whenever temperature increases.

Transistor Data Sheet*VCEO = measured from the collector (C) to emitter € with the base open (O).

4-4 The BJT as an Amplifier*Amplification - process of linearly increasing the amplitude of an electrical signal and is one of the major properties of a transistor.*A transistor amplifies current because the collector current is equal to the base current multiplied by the current gain β.

4-5 The BJT as a Switch*When used as a switch, a BJT is normally operated alternately in cutoff and saturation.

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Skipped "A Simple Application of a Transistor Switch" / "The Phototransistor" / "Transistor Categories and Packaging" / "Troubleshooting"

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- Silicon - 4 valence electrons- Germanium - 4 valence electrons- Gallium - 3 valence electrons- Arsenic - 5 valence electrons

1.1 Introduction*Jack Kilby (1958) - First Integrated Circuit (IC) "Phase-Shift Oscillator"*Intel Core i7 Extreme Edition Processor = 1.67"*Moore's Law = transistor count in a single IC chip will double every two years.

1.2 Semiconductor Materials: Ge, Si, and GaAs*Semiconductors = special class of elements having a conductivity between that of a good conductor and that of an insulatorTwo Types:1. Single-crystal (repetitive crystal structure) - Germanium and Silicon2. Compound (two or more semiconductor materials of different atomic structures)- Gallium Arsenide (GaAs), Cadmium Sulfide (CdS), Gallium Nitride (GaN) and Gallium Arsenide Phosphide (GaAsP)Ge, Si and GaAs - most frequently used semiconductors

Diode (1939), Germanium Transistors (1947), Silicon Transistors (1954), GaAs Transistors (Early 1970s)

Why Silicon is better? (1) Less temperature sensitive than Ge, (2) AbundantWhy GaAs is different? (1) 5x faster than Si, (2) is difficult to manufacture at high levels of purity and (3) had little design support, (4) more expensive

1.3 Covalent Bonding and Intrinsic Materials- Valence Electrons - electrons in the outermost shell- Tetravalent (four) / Trivalent (three) / Pentavalent (five)- Valence - indicates that the ionization potential required to remove any one of these valence electrons from the atom structure is significantly lower than that required for any other electron in the structure- Covalent Bonding - bonding of atoms, strengthened by the sharing of electrons- Free electron - applied to any electron that has separated from the fixed lattice structure and is very sensitive to any applied electric fields established by voltage sources or any difference in potential- Intrinsic - any semiconductor material that has been carefully refined to reduce the number of impurities to a very low level - essentially as pure as can be made available through modern technology- Intrinsic carriers - free electrons in a material due only to external causes- Doping - ability to change the characteristics of a material by adding impurities- Conductors (positive temperature coefficient) - higher resistance when heat increases, because current tends to move randomly, hence making it difficult to control the flow when heat is present- Semiconductors (negative temperature coefficient) - higher conductivity with the present of heat because valence electrons absorb sufficient thermal energy to break the covalent bond and contribute to the number of free carriers.

1.4 Energy Levels*The farther an electron is from the nucleus, the higher is the energy state and any electron that has lefts its parent atom has a higher energystate that any electron in the atomic structure.

1.5 N-Type and P-Type Materials*Extrinsic Material - a semiconductor material that has been subjected to the doping processTypes of Extrinsic Materials1. N-Type (donor atoms / electron majority/ hole minority)- Adding Pentavalent (five) semiconductors (Phosphorus, Antimony, Arsenic, Bismuth)*There is a fifth unassociated antimony electron.

Boylestad (Chapter 1 - Semiconductors)

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2. P-Type (acceptor atoms / hole majority / electron minority) - Adding trivalent (three) semiconductors (Boron, Indium, Gallium)*Hole - vacancy in the atom.

1.6 Semiconductor Diode:Semiconductor Diode: joining a p-type and n-type materialDepletion Region - region of uncovered positive and negative ions due to the depletion of free carriers in the region.Bias - refers to the application of an external voltage across the two terminals of the device to extract a response.No Bias - it acts like an isolated resistorReverse Saturation Current - the current that exists under reverse bias conditions Saturation - comes from the fact that it reaches its maximum level quickly and does not change significantly with increases in the reverse bias potential.

Conventional Flow - hole flow

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*The actual reverse saturation current of a commercially available diode will normally be measurably larger than that appearing as the reverse saturation current in Shockley's equation.*For every 5 degrees C increase in current, the level of reverse saturation*Higher doping levels, Double junction area, more temperature = more reverse current.*Breakdown Voltage - reverse bias potential that results in this dramatic change in characteristics*Ionization - happens when valence electrons absorb sufficient energy to leave the parent atom. *Peak Inverse Voltage - maximum reverse bias potential that can be applied before entering the break-down region

Material Knee Voltage Reverse Saturation Current Breakdown Voltages Operating Speed (Electron Mobility Factor)

Ge 0.3V (lowest) 1uA (highest) 100 - 400V (lowest) 3900

Si 0.7V 10pA As high as 20kV (highest) 1500 (lowest)

GaAs 1.2V (highest) 1pA (lowest) 50V and 1KV 8500 (fastest)

*Forward bias region: 1 degree Celsius increase = 2.5mV increase in voltage*Reverse bias region: reverse current doubles for every 10 degrees rise in temperature.

*Russel Ohl - accidentally discovered p-n junction after seeing a surge in current when a cracked Silicon crystal was near a light

1.7 Ideal Versus Practical*A semiconductor diode similar to a mechanical switch because it controls whether current can flow or not, but also a bit difference since current can only flow in a diode unidirectional

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current can only flow in a diode unidirectional

1.8 Resistance Levels*DC or static resistance (R) - the lower the current, the higher*AC or dynamic resistance ® - the lower the current and the voltage, the higher

*Dynamic Resistance =

*Average AC resistance - resistance determined by a straight line drawn between the two intersections established by the maximum and minimum values of input voltage.

1.9 Diode Equivalent Circuits

1.10 Transition and Diffusion Capacitance

Transition Capacitance - predominant capacitive effect in the reverse biasDiffusion Capacitance - predominant capacitive effect in the forward bias

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3.1 Introduction1904 -vacuum tube was the electronic device of interest and was introduced by J.A. Fleming1906 - Lee De Forest added a third element (control grid) to the vacuum diode, which resulted to triode, first amplifierDecember 23,1947 - first transistor by William Shockley, Walter Brattain and John Bardeen in Bell Telephone Laboratories.

3.2 Transistor ConstructionTransistor - three-layer semiconductor device (npn or pnp)DC biasing - necessary to establish the proper region of operation for AC amplificationEmitter (E) is more highly doped than collector (C) and base (B)150:1 width between the sandwiched layer (p) and outer layer (n) for npn or vice versa1:10 doping level between the sandwiched layer (p) and outer layer (n) for npn or vice versaBJT - Bipolar Junction TransistorBipolar - both holes and electrons participate in the injection process into the oppositely polarized material

3.3 Transistor Operation*One p-n junction of a transistor is reverse-biased whereas the other is forward-biased.

*Leakage Current (ICO) - minority carrier component of Ic (similar to the current when a diode is reverse biased.

*Common base configuration - the base terminal (B) is common to both the input and output*The arrow in the schematic points to the direction of the emitter in the conventional current flow.*Active Region - BE is forward biased and CB is reversed bias.*Cutoff Region - BE and CB are both reversed biased and Ic is zero!*Saturation Region - BE and CB are both forward biased.

3.4 Common-Base Configuration

*magnitude of alpha in dc and ac are almost the same.

3.5 Common-Emitter Configuration

*Common Emitter configuration - emitter terminal is common to both the input and output

Boylestad (Chapter 3 - Bipolar Junction Transistors)

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*HFE is dc and Hfe is ac.*Beta is usually between 50 to 400.*magnitude of beta in dc and ac are almost the same.*Region of negative resistance - region where current increase results to drop in voltage

3.6 Common-Collector Configuration

3.7 Limits of Operation*Maximum Collector Current (ICMAX) - continuous collector current*Maximum Collector-to-Emitter Voltage (BVCEO or VBR(CEO)) *Maximum Dissipation Level - Pcmax = VCEIC

*The two must not be both maxed.*Power Derating: 5mW for every 1 degree rise in temperature above 25 degrees

3.11 Transistor Development*Moore's Law - predicts that the transistor count of an integrated circuit will double every 2 years* III V Compound Semiconductors - will soon replace Silicon, due to its increased speed, reliability, stability, reduced size and improved fabrication techniques (e.g. InGaAs (Indium Gallium Arsenide)*Intel Core i7 Quad Core - 1.6" square containing 730 million transistors with 3.33 GHz. clock speed*Junctionless transistor - by a swedish team to simplify manufacturing process*Carbon Nanotubes - a carbon molecule in the form of a hollow cylinder that has a diameter about 1/50000 the width of human hair as a path toward faster, cheaper and smaller transistors.*Crossbar Latch - employs a grid of parallel conducting and signal wires to create junctions that act as switches

3.12 Summary1. Semiconductor devices have the following advantages over vacuum tubes: They are (1) of smaller size, (2) more lightweight, (3) more rugged, and (4) more efficient. In addition, they have (1) no warm-up period, (2) no heater requirement, and (3) low operating voltages.2. The collector current is made up of two components: the majority component and the minority current (also called the leakage current).3. A three terminal device needs two sets of characteristics to completely define its characteristics.4. The impedance between terminals of a forward-biased junction is always relatively small, whereas the impedance between terminals of a reverse-biased junction is usually quite large.

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4.1 Introduction*Any increase in ac voltage, current, or power is the result of a transfer of energy from the applied dc supplies.

4.2 Operating Point*Biasing - application of DC voltages to establish a fixed level of current and voltage*Quiescent Point (Q-point) - operating point (Ic is x, Vce is y)*Temperature increases the transistor current gain (Bac) and the transistor leakage current (ICEO)Operations:1. Linear-region Operation: BE is forward biased and BC is reversed bias.2. Cut Off Region: BE and BC are both reversed bias.3. Saturation Region: BE and BC are both forward bias.

4.3 Fixed-Bias Configuration*VCC can be divided.*For normal operations, Vc is positive and VB is negative.

Transistor Saturation - levels that have reached their maximum values*Maximum Ic and set Vce to zero!*To get Icsat, set Vce to zero.

Transistor Cut Off - no current running*Zero Ic and maximum Vce (equal to Vcc)

Load line Analysis - Graphical analysis of Ic vs Vce

Boylestad (Chapter 4 - DC Biasing - BJTs)

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4-4 Emitter Bias Configuration*May resistor sa emitter side, which provides improved stability. (The dc bias currents and voltages remain closer to where they were set by the circuit when outside conditions, such as temperature and transistor beta, change.

4-5 Voltage-Divider Bias Configuration:*This configuration is not beta dependent.

Exact Analysis (Use Thevenin's Theorem)

*Be wary when the emitter resistor is connected to a voltage source!Approximate Analysis (R1 and R2 are in series)

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4.6 Collector Feedback Configuration:(1) May nakaparallel na resistor sa Collector and Base(2) May resistor din sa emitter.

4.7 Emitter Follower Configuration:*May Voltage Source sa emitter.*Solve as normal.

4.8 Common Base Configuration:.*It has a very low input impedance, high output impedance and good gain.*Get Ie first.*Use Ie when computing for Vce and Ic when computing for Vcb.

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*Use Ie when computing for Vce and Ic when computing for Vcb.

4.11 Design Operations

ñ

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4.12 Multiple BJT Networks1. RC Coupling:

2. Darlington: Output of one is directly fed to the input of the other.

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4.13 Current Mirror*a dc network in which the current through a load is controlled by a current at another point in the network.

4.14 Constant Currents*Ie = i

4.17 Troubleshooting Techniques

Parameter Expected Problems

VBE ~0.7V *If zero, transistor is on off state.*If negative, then it may be a PNP transistor.

VCE 25% - 75% If 0V, it is on short circuit state or poor connection.If around 0.3V, it is saturated.

If 20V when VCC = 20V, faulty transistor or open circuit between BE or CE loop.

IB *If wrong current value, wrong resistance value.

*When measuring VBE, for NPN, red is on base (+) and black is on emitter (-).

4.20 Summary:*Operating point- defines where the transistor will operated on its characteristics curves under the DC conditions*Fixed-bias configuration is the simplest yet most unstable due to its sensitivity to beta.*To get Icsat, Vce = 0 or collector to emitter should be shorted.*To check the transistor, the BE voltage should be close to 0.7V and CE voltage should be 25% to 75% of Vcc (applied voltage).*In PNP transistors, the current directions are reversed and voltages will have the opposite polarities.*Beta is very sensitive to temperature and VBE decreases about 2.5mV for each 1 degree increase.*Reverse saturation currents doubles every 10 degree Celsius.*Networks with the smallest stability factors are most stable and least sensitive to temperature.*Switching configuration: transistor moves quickly between saturation and cutoff regions.

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7.1 Introduction*Between their inputs and output, BJT establishes a linear relationship due to beta being constant, while FET establishes a nonlinear relationship due to the squared term on the Shockley's equation.*BJT is current controlled (IB), while FET is voltage controlled (VGS).

General Relationships

*Conditions for plotting the curve:

7.2 Fixed Bias Configuration*Called fixed bias because VGS is a DC supply that is fixed in magnitude (VGS = - VGG)

*Both graphical and mathematical approaches can be applied.

*RG will be treated as a short.Condition for the intersecting line:

*The intersection is called the quiescent or operating point.*Coupling capacitors: are open during DC, and shorted(because of very low impedances during AC analysis.

7.3 Self-Bias Configuration*Eliminates the need for two dc supplies. (No voltage from the gate.)*RG will be treated as a short.*Can be solved graphically or mathematically.

Boylestad (Chapter 7 - FET Biasing)

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Condition for the intersecting line:

7.4 Voltage Divider Biasing

*Use Voltage divider to get VG:

*Increasing values of RS result in lower q-points and decreasing values of VGS.Conditions for the Intersecting line:

7.5 Common Gate Configuration*Walang laman si gate at connected directly sa ground.

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7.6 Special Case: VGS = 0 V*Both gate and source are grounded.

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6 - 1 The Unbiased Transistor*3 doped region - base, collector and emitter *n-type materials - electrons are the major carriers*p-type materials - holes are the major carriers*A transistor is similar to a back-to-back diode - emitter-base diode (narrower) and collector-base diode

6-2 The Biased Transistor*Most will continue on the collector side because (1) Base is lightly doped and very thin, which means that that the free electrons have a long lifetime in the base region. (2) The base is very thin that it can go to the collector quite easily due to short distance.

Malvino (Chapter 6 - Bipolar Junction Transistors)

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*Metal Oxide Semiconductor Field Effect Transistors: differs from JFET (1) gate is insulated, (2) gate current is lower than JFET*Sometimes called IGFET (Insulated Gate Field Effect Transistor)*Like JFET, it is also a "normally on" device because it has a drain current even if there is no gate voltage!*ID can exceed IDSS when VGS is positive.

Two Types of MOSFET:1. Depletion-mode type - normally used as RF amplifiers2. Enhancement-mode type - used in discrete circuits (as power switching) and in integrated circuits (digital switching)

14 - 1 The Depletion-Mode MOSFET

*More negative gate voltage = smaller drain current*More positive gate voltage = greater conduction from source to drain.

14-2 D-MOSFET Curves*VGS cutoff is negative instead of zero! ID here is zero.*N-channel JFET can never have negative VGS value, but n-channel DMOSFET can have, because there is no pn-junction to forward biased.

*If VGS is negative, DMOSFET works on depletion mode.*If VGS is positive, DMOSFET works on enhancement mode.*IDSS is not the maximum drain current anymore.

Malvino (Chapter 14 - MOSFETs)

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Skipped 14-3 Depletion Mode Amplifiers

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*Q-point determines the class of operation

Three Operation Regions1. Cutoff - Transistor is off2. Active - Voltage is equal or above the forward breaker voltage3. Saturation - Transistor is like a switch

Classes of Operation1. Class A - device is "on" or the active region during the entire waveform (360 degrees)*Least efficient because transistor has to be on and greater power needs to be applied.*gives the cleanest waveform

2. Class B - device is "on" for 1/2 cycle (180 degrees)*More efficient than class A since it has to be on for half of the cycle*More distortion

3. Class C - device is "on" for less than half of the cycle*Most efficient since it is off most of the time*Most distortion than B.'*RF Amplifiers

4. Class AB - devices is on between 180 and 360 degrees

FloydUses:Not used for linear amplification / Used for radio frequency (RF) applications, including circuits, such as oscillators, that have a constant output amplitude and modulators, where a high frequency is controlled by a low frequency signal.

Because of this they are not used for AM signals, but are used for angle modulated (FM or PM) signals since the modulation does not affect the amplitude.

How it works:1. Biased below cutoff with a negative Vbb supply.2. The ac source voltae has a peak value that is slightly greater than Vbb + Vbe so that the base voltage exceeds the barrier potential of the BE junction for s short time.

Tuned Operation:*Parallel resonant circuit (tank) is needed since the collector voltage (output) is not a replica of the input, which makes of it of no value in linear amplification. *The short pulse of collector current on each cycle of the input initiates and sustains the oscillation of the tank circuit so that an output sinusoidal voltage is produced.

Class Amplifiers

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When the tank circuit is tuned to the frequency of the input signal (fundamental), reenergizingoccurs on each cycle of the tank voltage,

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The amplitude of each successive cycle of the oscillation will be less than that of theprevious cycle because of energy loss in the resistance of the tank circuit, as shown inFigure 7–26(a), and the oscillation will eventually die out. However, the regular recurrences

of the collector current pulse re-energizes the resonant circuit and sustains the oscillationsat a constant amplitude.

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2.1 IntroductionIN 4001 - Silicon Diodes

2.2 Load Line

2.9 Clampers

Clampers - a network constructed of a diode, a resistor and a capacitor that shifts a waveform to a different DC level without changing the appearance of the applied signal

*Have a capacitor connected directly from input to output with a resistive element in parallel with the output signal.

Start the analysis by examining the response of the portion of the input signal that will forward bias the diode.1.During the period that the diode is in the "on" state, assume that the capacitor will charge up instantaneously to a voltage level determined by the surrounding network.

2.

Assume that during the period when the diode is in the "off" state the capacitor holds on to its established voltage level.

3.

Throughout the analysis, maintain a continual awareness of the location and defined polarity for v0 to ensure that the proper levels are obtained.

4.

Check that the total swing of the output matches that of the input.5.

Steps in solving Clampers:

Chapter 2 - Diode Applications

Elecs 1 Page 33