Semiconductors and Diodes

• Module 04 covers electronic fundamentals.

Semiconductors

• Semiconductor circuits use silicon (Si), germanium, or gallium arsenide.
• Electrical properties depend on the number of valence electrons in the outermost electron shell.
• Valence shell refers to the outermost electron shell of an atom.
• Valence electrons are the electrons within the valence shell.
• Valence electrons significantly influence a material's properties and interaction with other atoms.

Diode Characteristics

• Silicon diodes feature a crystalline grid structure akin to a square-based pyramid and have four valence electrons.
• Doping increases semiconductor conductivity via the introduction of other atoms into a pure semiconductor's crystalline grid.
• Silicon diodes incorporate impurities with three or five valence electrons in their outer shell.
• Silicon crystal impurities result in an excess of electrons on one side of the crystal and a deficiency on the other.

P and N Type Semiconductors

• Atoms with three (trivalent) or five (pentavalent) valence electrons create semiconductor conductivity.
• Trivalent atoms insert holes, while pentavalent atoms insert more electrons.
• A hole signifies the absence of an electron in a covalent bond, acting as a free charge in the material.
• N-type material results when pentavalent atoms are added, the conductivity happening due to electron movement making them negatively charged (cathode).
• P-type material results when trivalent atoms are added; hole movement causes material's conductivity; material charged positively (anode).
• In the junction zone, an interaction occurs due to excess holes in the p-side and excess electrons in the n-side.
• A current flows in a directly polarized diode, leading to electron-hole recombination near the junction, decreasing electron energy.

PN Junction

• Some electrons move from the n-side to the p-side via the junction and fill holes in the p-side.
• This electron movement creates a positive charge in the n-side and a negative charge in the p-side, leaving both sides near the junction without charge carriers.
• When a hole moves from the P to N region, recombination increases in that area.
• The space charge region/depletion layer refers to this area.
• Increasing reverse bias raises the potential barrier, opposing majority carriers while freeing minority carriers.

Diode Characteristics (Current and Conduction)

• A diode's current amplitude is determined by its polarization.
• The diode will not conduct if the circuit's negative part connects to its positive part.
• There's a direct correlation between voltage and current; above a threshold voltage, a significant charge movement occurs, initiating current flow.

Diode Parameters

• A diode is a non-linear electronic passive device, where the voltage curve's positive region shows an exponential and nonlinear trend.
• Current in a directly polarized diode flows due to charge majority carriers, increasing rapidly with voltage, typically at 0.7V.
• If a diode is in reverse polarization and diode voltage is increased until a certain "breakdown value,” a reverse current quickly increases and diode breakdown happens.
• Zener diodes function normally in the breakdown region, making this not always destructive.

Diode Symbols

• Diodes come in various types: Schottky, Varicap, Light Emitting Diode (LED), and Photo-diode.
• The negative terminal distinguishes the symbols of different types of diodes.

Diodes in Parallel

• Diodes connected in parallel with output terminals limit voltage peak values.
• If input voltage (Vi) exceeds reference voltage (Vr), the diode enters direct polarization.
• The input current goes through the diode because of low resistance, creating a short circuit in the parallel branch.
• The reference battery dictates the wave-cut value.
• This circuit type is known as a CLIPPER.

Diodes in Series

• A diode functions as a passive switch within an AC circuit for current wave rectification.
• Diode is connected in series with the output branch of the circuit when used as a rectifier.
• If the input voltage (Vi) is less than the reference voltage (Vr), the diode is non-conducting, maintaining the output voltage (Vo) equal to Vr.
• The diode becomes directly polarized when the input voltage surpasses the reference value, making the output voltage almost equivalent to Vi.

Voltage Rectifier

• Another diode in opposition is needed to rectify the entire sine wave and split the secondary voltage in two equal parts with a central pin.
• The diode D1 polarizes directly when the voltage wave is positive and diode D2 will be in reverse polarization and vice versa when the wave is negative.

Graetz's Bridge Circuit

• Rectifier circuits convert voltage waves from an average value of 0 into a new always-positive state with a different average value.
• There are three rectifier circuit types: one diode, two diodes, and Graetz's bridge rectifier.
• Only two opposing diodes directly polarize during one half of the voltage wave in a full-wave Graetz's bridge rectifier.
• The conducting diodes switch when voltage polarity inverts to maintain an output voltage equivalent to that of the two diodes rectifier.

Rectifier with Capacitive Filter

• Capacitive filters equalize pulsing voltage from rectifier circuits: the diode polarizes directly in the voltage wave's first quarter, charging the capacitor.
• When the voltage declines, the capacitor which is connected in parallel to the load, discharges until the ensuing positive half wave recharges it.
• Consistent capacitor charging and discharging equalizes a fluctuating voltage signal.

Clamper Circuits

• A clamping circuit is known to restrict the upper or lower limit of a waveform to a set DC voltage level.
• These circuits are also referred to as DC voltage restorers.
• Clampers can be made with both positive and negative polarity, including both biased and unbiased versions.

Thyristor (SCR)

• The thyristor is a controlled silicon rectifier (SCR) that acts like a diode controlled by current impulse; its has low resistance when switched on and high resistance when it's switched off.
• It comprises three connection points: the anode, cathode (like a diode), and a gate.
• Conduction takes place only when electric current flows through the gate acting as the device's control terminal.

Light Emitting Diode

• LED stands for light emitting diode. It's a junction electronic device created using particular semiconductor materials that produce light when electricity passes through these materials.
• Normal silicon diodes release thermal energy when reverse biased, whereas LEDs emit light.
• Doping material determines LED color.
• The maximum reverse voltage of LEDs is between 3-5 volts, with a current range of 5 to 20 milliamperes.

Photo Diode

• The photo-diode operates in reverse polarization
• Tangible reverse current is generated when light is run over the reverse biased photodiode producing free charge carriers.
• That current is dependent on light intensity and wavelength.

Varistor

• The varistor acts as a voltage-dependent resistor.
• Typically, it protects devices from unforeseen voltage peaks; decreasing the voltage flow and resistance value it protects other electronic devices.
• The varistor curve exhibits symmetry, resembling two diodes in reverse polarization.
• Its electrical symbol represents two opposing diodes for this reason.

Varicap and Schottky Diodes

• Varicap diodes function as variable capacitors, changing capacity based on voltage, instead of normal silicon diodes.
• The varicap diode symbol is thus shown like a diode connected in line with a variable capacitor and can have capacities between picofarads and numerous picofarads.
• Schottky barrier gives Schottky diodes a low forward-voltage drop (0.15-0.45V) and good high-frequency performance by creating a metal-semiconductor junction.
• The largest limitation of Schottky diodes is relatively their high reverse leakage current.

Zener Diodes

• Zener diodes function in breakdown zones, maintaining a steady reverse breakdown voltage of 5-6V, enabling their use as voltage stabilizers.
• The semiconductor doping and material resistivity determine the Zener voltage.
• Zener diodes function as voltage stabilizers when connected in parallel to the load on the output branch of a circuit.

Digital and Analog Multimeter

• Functional diode testing with a multimeter will help determine the cathode and anode of a diode.
• The measurement of current, voltage, and resistance can be done by a digital and analog electronic instrument referred to as a multimeter.
• The diode's forward bias check involves putting the positive lead of the ohmmeter to the anode.
• Diode damages can be verified by using a multimeter.

BJT Bipolar Junction Transistor

• BJT transistors utilize silicon and have an input resistance that contrasts with the output resulting in differing input and output resistance.
• Its three key parts are collector, emitter, and base.
• The EMITTER sends out or emits “current carriers” (electrons or holes).
• Current carrier flow is regulated by the BASE.
• Current carriers are collected by the COLLECTOR.
• BJT transistors control a high output current with low input current.
• NPN and PNP are types of transistors that charge carriers (holes and electrons) allow current to pass.

NPN Junction Interaction

• Emitter current is divided into collector and base current.
• Base current (IB) is usually 2-5% of the total current, whereas collector current (IC) typically makes up the remaining 95-98%.
• The small variations in emitter-base have large impacts on the magnitude of collector current with relation to overall emitter-to-collector current.

Transistor Types (NPN and PNP)

• In PNP and NPN transistors, the letter specifies emitter polarity, followed by the base, and collector.
• To amplify, transistor must have the emitter base being forward biased and collector base being reverse biased.
• In NPN transistors the emitter connects to the negative side of a battery.

PNP Transistor - Forward/Reverse Biased Junctions

• Forward-Biased Junction:
  • Battery positive terminal causes emitter holes to go towards base, while negative terminal drives base electrons toward emitter.
  • Movement of electrons constitutes base current and creates emitter base circuit.
• Reverse-Biased Junction:
  • Negative voltage on collector and positive voltage on base limits charge passage through the junction.
  • Electrons flow from negative terminal and fill holes in collector.
  • The inverse biased connection only sees a negligible minority current because the number of minority charge carrier electrons is limited.

Transistors: PNP

• Majority charge carriers are holes for PNP transistors and thus the batteries are reversed whereby the base is negative with respect to the emitter, and the collector is negative to the base.
• If the base is negative to the emitter flow of conventional happens when the emitter has a more positive bias and is due to current flow in the holes.

Common Base/Emitter Configuration

• The emitter configuration that is most common for amplifiers provides great voltage and current gain along with high powered gain.
• This configuration gain is indicated by the letter beta (β), ratio of the collector current, and relates to the base current.

Common Base/Collector Configuration

• High voltage and low current gain are produced by a common base configuration. Current gain can be calculated as Ioutput/Iinput and the the collector and emitter determine an a = lc/le
• Since as said before, the collector current is about 99% the emitter current gain is less than one.
• Need to identify ration Vo / Vi to identify voltage gain.
• Use of the least common collector produces a weak voltage gain (Av) even if this produces good amplification.
• The current gained from this configuration (y) corresponds to the ratio of emitting IE current in direct to base IB in another.

FET Transistor

• FET transistor operations relies on the impact a transverse electrical sphere has on electrical movement that modifies the number in the semiconductor. As such it is viable for varying conductance with current that in effect reverses the source via application of voltage on a loop current that feeds back into the device.
• A bar bar featuring N or P charges lies within the architecture of N or P charge areas respectively.
• Drain (D), gate (G), and source (S) are three electrical connections that are made.
• Originally current ID values rise with respect to current VDS There is more and more in every increment, so changes in current do not have a meaningful impact on current values.

MOS Transistor

• MOS transistors unlike junction FET are unipolar devices. In effect charges can only follow in electrons or holes.
• The crucial feature in MOS transistors is their high resistance.
• Depletion MOS transistors include source, gate, drains and bulk gate and a bulk gate. Depletion placement is inside silicon which connect source with inside the device so each unit has both 3 in 3.
• In the source, it must combine with the help of connected enhancement in order for them to create electrical connections on the metal surface to have full performance from the transistors.

Amplifiers

• Amplifiers may be sorted as either voltage or current amplifiers depending on the nature of the electrical signal that goes into or comes out of such circuits
• Power amplifier class varies depending on duration of input signal it amplified.

The three power classes of amplifiers:

• Class A Amplification: This is amplifying a total number over the input, so it should produce about 360 degree.
• The amplifier class B is responsible when it amplifiers and then there should be 180 degrees.
• This means the AB of classes of magnification ranges is usually about approximately 180degree at 360.
• It amplifies classes of less signals and as well at that it is said if it to about <180degree.

Amplifiers (Connecting in Series)

• Most single amplifier setups are insufficient and this calls for extra chain amplifiers. Circuits called circuits coupling for circuit amplifiers and in amplifiers, the circuits must come together in certain combinations.
• A configuration known to circuits for coupling involves the use of a direct capacitor with an inductor.
• In AC capacitors they also must be used to use resistors to make DC bypass to allow only AC without the electrical interference.

Oscillators

• Circuitry that are capable signal generation with specific frequencies are called oscillators.
• Every oscillators will need electrical current even to function to signal output.
• Circuits are made dynamic when they implement 3 or more inputs as well to as two transistors in between circuits.

The creation of oscillations can come through two techniques:

• Capacitors, Inductors, and Bipolar Junction Transistor. These are electrical connections often that can be used to create the harmonic sounds.
• Implementation of two capacitors, as well in harmonic functions, is also viable with circuit components as a harmonic as circuits.

Monostable and Bistable Multivibrators

• Monostable multivibrators have completely and stable states that is near stable but do not last.
• A bistable multivibrator consists of two stable states that have time that is indefinite.
• Since state has limited to about two, it is very suitable with implementing binary electrical components. With this said device it may function in lieu of a flip flop.
• Common emitter setups uses two silicon transistors (BJT) together in conjunction to the configuration's resistive.

Logic Gates - NOT Gate

• A NOT logic gate circuit has 2 states that are both high and low.
• It has one input, has one output, inverts signal or negates status, uses a bar to symbolize the logic (output in general).
• The table for truth has 2 results with one each from inputs, because the electricals has 2 inputs of 0 and 1.

Logic Gates - AND Gate

• The AND gate carries logic by one or both inputs then send only an output is "S".
• Its expression in theory equates to AB=s.
• While those has a few inputs on a logic gates but all will behave the same as two if more are applicable.
• There are truth table value where an input has 1 and both values must have an equal amount of "1" or this equal the value is wrong.

Logic Gates - OR Gate

• The expression comes into two value that A+B=S and 1s are equal.

Logic Gates - NAND Gate

• The logic in one can derive one can also include a gate not as well. Not A not B = S
• If is a gate to output the results so electrical connection that results is the same.

Logic Gates - NOR Gate

• The expressions with the electrical and the product is the same for results.
• With a circuit to have the ability in and outside must have no connection with any signal or it will not follow any output. Not and out B from it produces equals the same product S in electrical.

Operational Amplifier

• Multi stage amplifiers of high gain are known under operational amp that has and does have loop open and close.
• A circuit that has is required characteristics with an amplifier. With the 3 most of the characteristics for implementation.
• very High in both resistance, low outer, voltage, impedance.
• There the two symbol electrical call non-inverting with a polarity, and inverting. All of inputs must require some type circuit.

Operational Amplifier - 2nd and 3rd Stages

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• Final stages are the amplifier which make the low available from everything from the the point that can be from everything available at the inputs.

Operational Amplifier (Output Relations)

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Operational Amplifiers in Open Loop

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Close Loop Operational Amplifiers

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PCB: Printed Circuit Boards

• PCB provide mechanical support with electrical connection for components of circuit.The metallic path ways provides for connection circuit.The terminal components of board where the metallic and holes are is what welding comes onto.

PCB: Manufacturing Process

• Connections are done by depositing the conductor on board where single or multiple components are covered with Welding Alloy.
• Post boards construction, electrical tests are performed to test circuit connection. Most usage involved infrared tecnograph but photoresist is another viable and engraving one.

PCB: Thickness pathway width

• With current thickness is 25-75. The pathways wide most or will can reach 1-2. There is as will space which reach to least 1mm as well.
• A product can do everything design with electrolytic connections on copper plate by welding and installing its electrical.

PCB: Micro modules

• Micro modules contain thin simple circuit cards. When each is electrically connected they output its desired current but may also output something else. Thickness is at roughly 0.001 which is about 8.0 to 9 for electrical to be there at. There the and the which this happens one metallic electrical with chemicals.

PCB: Hexanoal And Micro

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Open And Close Loop Controls

The purpose of Control system is to linked a group components that perform a specific function. The control can have more power by one input and one output, the system be on which one has better signal.