P64Comp Handout 1: Temperature and Heat Review Summary PDF

P64Comp Handout 1: Temperature and Heat Review Summary 1. Heat and temperature are related but NOT the same concepts. a. The subjective perception of “hot” or “cold” is related to an object’s temperature. Thus, the common definition of temperature is it is a measure of the “hotness” or “co...

P64Comp Handout 1: Temperature and Heat Review Summary 1. Heat and temperature are related but NOT the same concepts. a. The subjective perception of “hot” or “cold” is related to an object’s temperature. Thus, the common definition of temperature is it is a measure of the “hotness” or “coldness” of an object. b. Temperature directly relates to properties of objects. In chemistry, objects with high temperature are found to have molecules with high kinetic energy and vice-versa. c. An object’s temperature is measured using a thermometer, which is dependent on the properties and behavior of matter during a temperature change 2. Heat, on the other hand, is a form of kinetic energy. a. Heat is energy transferred between objects of different temperatures. Heat is not temperature (NOT synonymous); heat is what flows when there is a temperature difference. b. Heat flows from an object of higher temperature to an object of lower temperature. c. Because heat is energy, the quantity of heat is expressed in Joules (J). 3. Because heat is energy transferred between objects of different temperatures, a. Heat will transfer from an object of high temperature to an object of low temperature b. Heat will not flow if the temperature of both objects are the same; this is called thermal equilibrium 4. The measurement of temperature is dependent on the behavior of matter during temperature changes. Temperature can be measured through: a. Changes in volume in solids and liquids b. Changes in pressure in gases c. Changes in resistivity 5. Temperature scales are temperature measurements based on properties of matter. The more common temperature scales are: a. Celsius temperature scale – This is also known as the centigrade scale, because it is based on the freezing point (00C) and boiling point (1000C) of water (all at standard atmospheric pressure) and has 100 degrees in between. b. Fahrenheit temperature scale – This scale is also based on the freezing point (320F) and boiling point (2120F) of water at standard atmospheric pressure. The Fahrenheit degree is 5/9ths of a degree in the Celsius scale.  c. Kelvin temperature scale – The Kelvin scale is based on the changes in pressure and consequently temperature of gases in fixed volume containers. By extrapolation from pressure – temperature graphs, the zero temperature (absolute zero or 0 K) is determined to be at −273.150 𝐶. The Kelvin scale is not degree-based and is thus written without the degree sign. 6. Matter expands when temperature is increased. This expansion can either be linear or volumetric. a. Linear expansion: ∆𝐿 = 𝛼𝐿0 ∆𝑇, where ΔL is the change in length, L0 is the original length, and ΔT is the change in temperature b. Volume expansion: ∆𝑉 = 𝛽𝑉0 ∆𝑇, where ΔV is the change in volume, V0 is the original volume, and ΔT is the change in temperature c. The coefficients of linear (α) and volume (β) expansion depend on the kind of material that experiences the temperature change. 7. Thermal conductors are materials that permit the transfer of heat while thermal insulators are materials that prevent the transfer of heat. 8. There are three main methods of heat transfer: a. Conduction – transfer of heat between two bodies in contact b. Convection – transfer of heat through the motion of a mass from one place to another (more commonly in liquids and gases, because of their ability to flow) c. Radiation – transfer of heat through electromagnetic radiation P64Comp Handout Number 2: ELECTRICITY and ELECTRIC CIRCUITS 1. The following are the basic parts of an atom and their properties: Name of Particle Mass Charge Location Electron 9.11 𝑥 10−31 𝑘𝑔 −1.6𝑥10−19 𝐶 Orbiting around nucleus Proton 1.67 𝑥 10−27 𝑘𝑔 +1.6𝑥10−19 𝐶 Inside nucleus Neutron 1.68 𝑥 10−27 𝑘𝑔 𝑒𝑙𝑒𝑐𝑡𝑟𝑖𝑐𝑎𝑙𝑙𝑦 𝑛𝑒𝑢𝑡𝑟𝑎𝑙 Inside nucleus 2. Since an atom carries both positive (protons) and negative (electron) charges, there are several possible combinations: a. There is an equal number of protons and electrons, so the atom is electrically neutral b. There are more protons than electrons, so the atom is positively charged c. There are more electrons than protons, so the atom is negatively charged 3. To create a charged atom, the following considerations are taken into account: a. The proton is inside the nucleus and a lot of energy is needed to remove it from there b. The electrons are in orbit outside of the nucleus and would take less energy to remove 4. Thus, a charged atom can be achieved by adding or removing electrons from a neutral atom: a. Electrons are removed to create a positively charged atom b. Electrons are added to create a negatively charged atom 5. The following are the fundamental concepts relating to electric charge: a. The basic unit of the electric charge is ±1.6𝑥10−19 𝐶 b. Like charges will repel, unlike charges will attract c. Charges can create individual electric fields that can then interact 𝑞1 𝑞2 d. The interaction of charges are governed by Coulomb’s Law: 𝐹 = 𝑘 𝑟2 6. Electric charges can exist in vacuum or space but they can also travel through materials. a. Conductors are materials that allow electric charges to flow through them b. Insulators are materials that do not allow electric charges to flow c. Generally speaking, the difference between insulators and conductors is the number of “free” electrons; conductors have more 7. The flow of electric charge is called an electric current. Electric currents are propagated in electric circuits. Circuits are closed loops of conducting material with a potential difference. ∆𝑞 a. Current is defined as the flow of charge per unit time: 𝐼 = ∆𝑡 and its unit of measurement is the ampere (A). b. Voltage is sometimes referred to as electric potential difference or electromotive force (emf). It is defined 𝑊 as the work done per unit charge: 𝑉 = and its unit of measurement is the volt (V). 𝑞 c. Resistance is the action of a material to the passage of charge through it. The property connected to 𝐿 resistance is called resistivity. Resistivity is measurable through several properties of a material: 𝑅 = 𝜌 𝐴 and its unit of measurement is the ohm (𝛀). 8. An Ohmic circuit obeys Ohm's Law: 𝑉 = 𝐼𝑅, where R is constant. A non- Ohmic circuit is one that does not have a constant resistance. A light bulb is a simple example; the filament undergoes huge changes in temperature when current passes through it. For the sake of simplicity, we will only study Ohmic circuits. 9. Circuits can also be classified as either direct current (DC) or alternating current (AC) circuits. This depends primarily on how current is propagated across the circuit. For our purpose, it is sufficient to focus only on direct current circuits. 10. It is possible to combine resistors in circuits in two ways: series or parallel. 11. The following are the equations in relation to series and parallel circuits (with three resistors attached): Series Parallel Voltage 𝑉𝑇 = 𝑉1 + 𝑉2 + 𝑉3 𝑉𝑇 = 𝑉1 = 𝑉2 = 𝑉3 Current 𝐼𝑇 = 𝐼1 = 𝐼2 = 𝐼3 𝐼𝑇 = 𝐼1 + 𝐼2 + 𝐼3 Resistance 𝑅𝑇 = 𝑅1 + 𝑅2 + 𝑅3 1 1 1 𝑅𝑇 = + + 𝑅1 𝑅2 𝑅3 Physics 101, Handout Number 3: Notes on VACUUM TUBES 1. Vacuum tubes are the first devices to attempt some form of control of currents, and to apply this control to various devices. Electron Emission 2. For a current in a traditional circuit, electrons are set in motion within the circuit; electrons do not leave the wire. 3. The motion of the electrons (and atoms) is affected by temperature. If enough heat is applied, electrons can acquire enough kinetic energy to be emitted into the surrounding space. The electron emission due to heat is called thermionic emission. 4. There are four possible ways by which electrons can gain energy to escape: a. By evaporation or application of heat b. By bombardment of small, high speed particles like other electrons c. By photoelectric effect d. By placing it near an object of high potential 5. In a tube (normally in vacuum), the electron “current” is forced to fly off in space, emitted by the cathode (negative) and captured by the anode (positive). Note: Recall difference between conventional current and electron flow. The Diode Tube 6. Diodes have two basic parts: (a) an emitter of electrons (cathode) and (b) a receiver of electrons (anode). There are also two types of diode tube cathodes: (a) directly heated, referred to as filament cathode and (b) indirectly heated, referred to as cathode. 7. The plate consists of the anode that receives the emitted electrons. When the plate receives the electrons, it can heat up (and “glow”) because of: a. The heat from the filament or cathode b. The electrons striking the plate 8. Too much heating may cause the plate to itself release electrons. If electrons travel both ways, then the diode is now acting like a resistor. Heat of the plate is controlled by: (a) dull, black finish (blackbody radiation); (b) fitted radiator fins; or (c) water cooling. 9. To achieve reliable cooling, diode tubes must be “evacuated” (air is removed, thus a vacuum tube) to prevent the creation of ionized gas. 10. The characteristic diode curve of current versus voltage is shown below. Note that at 0V there is still a current because of “stray” electrons and that the current reaches a maximum value called the plate current saturation. In this case, there is no electron cloud around the plate; the electrons are immediately absorbed by the plate. Increasing the voltage once plate saturation point is achieved results in the plate itself releasing electrons. The Triode Tube 11. The triode tube consists of three elements: cathode, plate, and grid. While diodes were used to control currents only, triodes could be used as amplifiers because of the grid. The drawings below represent the schematics of a triode (top is anode, middle is grid, bottom is cathode). 12. A grid functions by “screening” the electrons hitting the plate. A grid attached to the positive terminal of a voltage source will increase the flow of electrons. A grid attached to the negative terminal of a voltage source will reduce the flow of electrons. 13. The grid controls the flow of electrons from cathode to plate. It means that it also controls the plate current and voltage. Changing the voltage of the source attached to the grid changes the plate voltage. For example, by changing the grid voltage by 1 volt, the plate voltage can be changed by 50 volts; this is an amplification of 50:1. We can measure the amplified voltage by: 𝑉𝑎𝑚𝑝𝑙𝑖𝑓𝑖𝑒𝑑 = 𝜇 𝑥 𝑉𝑠𝑖𝑔𝑛𝑎𝑙 , 𝑤ℎ𝑒𝑟𝑒 𝜇 𝑖𝑠 𝑡ℎ𝑒 𝑎𝑚𝑝𝑙𝑖𝑓𝑖𝑐𝑎𝑡𝑖𝑜𝑛 𝑓𝑎𝑐𝑡𝑜𝑟 Physics 101, Handout No. 4: Notes on SEMICONDUCTORS and DIODES 1. In solid materials, electron energy levels form bands of allowed energies, separated by “forbidden” bands. Two bands are of interest here: a. Valence band, the outermost band filled with electrons b. Conduction band, the band next to the valence band that is either partially filled or empty 2. These bands are separated by a band gap, which is the energy difference between the valence and conduction bands. Electrons in a completely filled band cannot move within the band; they have to gain energy and jump to the higher band. Electrons on a partially-filled band are free to move within the band. 3. Solids can be classified based on the characteristics of the bands and the gap: a. Insulators, where the band gap between valence and conduction bands is wide (3 t0 6 eV) b. Semiconductors, where the band gap is small (about 0.1 to 1 eV) c. Conductors, where the valence band is only partially filled and the adjoining band overlaps with the valence band (𝟏 𝒆𝑽 = 𝟏. 𝟔 𝒙 𝟏𝟎−𝟏𝟗 𝑱) 4. Semiconductors have a small band gap; in silicon, it is 1.1 eV and 0.7 eV in germanium. Electrons in semiconductors can move from the valence to the conduction band by acquiring energy: a. At 𝑇 = 0, there are no electrons in the conduction band and the semiconductor does not conduct b. At 𝑇 > 0, some electrons gain enough energy to overcome the gap and jump to the conduction band 5. Electrons moving to the conduction band from the valence band leave a “hole” (a covalent bond with a missing electron). If an electric field is applied to the semiconductor, electrons can jump into the hole, creating a new hole. A succession of jumps and holes creates a current. 6. Holes are p-type charge carriers while conduction electrons are n-type charge carriers. In pure or intrinsic semiconductors, the number of holes and conduction electrons are equal. In doped or extrinsic semiconductors, another material is added so that there are either more holes (p-type) or there are more electrons (n-type). 7. Below are electron diagrams of two dopants used in semiconductors. Antimony (atomic number 51) is considered as a pentavalent (5 electrons) dopant while boron (atomic number 5) is a trivalent (3 electrons) dopant. 8. For n-type materials, the dopant (or added material) will have 5 valence electrons; 4 electrons to bond covalently with surrounding silicon atoms, one electron left over. The “free” electron will need a small amount of energy to transfer to the conducting band (about 0.05 eV). So an n-type semiconductor has conduction electrons and no (extrinsic) holes. 9. For p-type materials, the dopant has 3 valence electrons; the 3 electrons will bond covalently with the surrounding silicon, leaving the fourth one empty (hole). So a p-type semiconductor will have mobile holes and no (extrinsic) free electrons. 10. Doped semiconductors are more versatile than pure semiconductors: a. The conductivity can be adjusted by choosing the doping fraction b. The majority carrier can be chosen; either electrons or holes can be used c. Junctions between p-type and n-type semiconductors can be made depending on need (for diodes or transistors) 11. The p-n junction is a semiconductor that changes abruptly from the p-type to the n-type. The movement across the junction is because of a difference in “concentration”. If there is no electric field to affect the material, holes will diffuse across the boundary and move into the n-type material  to capture electrons. Electrons will also diffuse across the boundary and fall into the holes. When this happens, charged ions are left behind on both sides. 12. A diode is a biased p-n junction with voltage applied across it. a. A forward biased diode has a p-side more positive than the n-side and the direction of the electric field is from the p-side towards the n-side. This means that holes are pushed across the p-n boundary and electrons are pushed across the n-p boundary. So a current flows. b. A reverse biased diode has an n-side more positive than the p-side and direction of the electric field is from the n-side towards the p-side. This pushes the charge carriers (holes and electrons) away from the p-n boundary. The depletion region widens and no current flows. Physics 101, Handout No. 5: Notes on SOLID STATE DEVICES (Transistors) 1. Solid-state devices are electronic devices in which electricity flows through solid semiconductor crystals (silicon, gallium arsenide, germanium) rather than through vacuum tubes. The science of electronics was founded on the ability of the electron tube (e.g. vacuum tube) to generate, amplify, and control an electric signal to accomplish a wide variety of functions. 2. In terms of technological development, the vacuum tube was replaced by the transistor due to the following advantages: a. Transistors use solid crystalline material rather than electron “gas” for electrical conduction; b. Transistors can perform the same functions as the tube but do it faster, more cheaply, and more reliably; and c. Transistors occupy significantly smaller amounts of space and consumes a proportionally smaller amount of energy. Transistors 3. The word transistor comes from TRANSfer and resISTOR. This is because the device performs the function of transferring an input-signal current from a low-resistance circuit to a high-resistance circuit. The transistor follows the same basic principle as the p-n junction except that now two such junctions are required (either PNP or NPN). 4. There are three basic elements in a two-junction transistor: a. EMITTER, which gives off or ‘emits’ current carriers (either electrons or holes) b. BASE, which controls the flow of current carriers c. COLLECTOR, which collects the current carriers 5. There are two types of transistors, based on how the p-n junctions are arranged: 6. The direction of the arrow in the emitter shows which of the two types of transistor is being referred to. If the arrow points in (Points iN), the transistor is a PNP. If the arrow points out (Not Pointing iN), the transistor is an NPN. The arrow always points in the direction of hole flow. 7. Transistor theory: a. A forward-biased PN junction is comparable to a low-resistance circuit b. A reverse-biased PN junction is comparable to a high resistance circuit c. If a crystal contains two PN junctions, one forward-biased and the other reverse-biased, a low- power signal can produce a high-power signal (𝑃 = 𝐼 2 𝑅) if the input junction is forward-biased and the output junction is reverse-biased. 8. NPN transistor operation: a. The majority carrier in an NPN transistor are electrons. b. The emitter (N) is connected to the negative side of the battery while the base (P) is connected to the positive side (first p-n junction) c. The collector (N) is connected to an opposite polarity voltage and it should be more positive than the base 9. The figure below shows which is the forward-biased and reverse-biased parts of the transistor: 10. The NPN junction interaction is summarized in the figure below. Note that: a. The collector voltage is generally higher than the base voltage (𝑉𝑐𝑐 > 𝑉𝑏𝑏 ) b. The current in the external circuit is due to the movement of free electrons from negative terminals of the supply battery to the n-type emitter, which is labelled emitter current (𝐼𝑒 ) c. Since the emitter-base junction is forward-biased, electrons move from the emitter to the base where the electrons become a minority carrier (since the base is p-type and will have more holes than electrons)  d. For each electron that combines with a hole in the base, another electron moves out through the base which creates a base current (𝐼𝑏 ) that returns to the base supply battery (𝑉𝑏𝑏 ). e. To ensure that only few electrons combine with holes in the base, the base region is only very lightly doped (very few holes). f. Most of the electrons that move into the base are subjected to a strong collector bias which accelerates the electrons towards the collector where they become majority carriers (collector is n- type) and they can move easily to the collector supply battery (𝑉𝑐 ) as collector current ((𝐼𝑐 ). g. The collector is physically larger than the base to: (1) increase the chance of collecting carriers and (2) enable the collector to handle more heat without damage. h. The total current in an NPN transistor is equal to the emitter current, which is distributed between the base current (about 2 to 5 percent) and the collector current (about 95 to 98 percent) 𝐼𝑒 = 𝐼𝑏 + 𝐼𝑐 i. A small change in the emitter-base bias has a greater effect on the collector current than it will have on the base current. 11. Simply summarized, the NPN transistor can be “switched on” thus: a. First, the base – emitter side is attached to a positive – negative source, respectively. The base – collector side is attached to a negative – positive source, respectively. b. Because of the polarity of the emitter, electrons migrate towards the base (in the form of a current) and from the base to the collector. This is the “on” state of the transistor. c. The small current that occurs in the base makes a big current flow between emitter and collector. Thus, the base is used to amplify the current. d. In this situation, the base-emitter pair is acting like a forward-biased diode while the base-collector pair is acting like a reverse-biased diode. 12. The PNP junction interaction is similar to the NPN transistor except that in the PNP transistor the majority current carriers are holes. 13. In the normal operation of the pnp transistor, positive voltage is applied to the emitter and the negative voltage to the collector. a. If the emitter-base junction is forward-biased, holes flow from battery into the emitter and move to the base. Some holes will combine with electrons in the base but most will be able to move from base to collector. b. Holes in the collector move into the negative terminal of the battery in the form of a “collector current”. The size of this current depends on how many holes are not captured by in the base. c. The number of captured holes can be controlled by the size of the “base current” so “collector current” is dependent on “base current”. 14. A transistor can be used as: a. An amplifier of base current since small changes in base current cause big changes in collector current. One of the first uses for transistors are in hearing aids. b. A switch, where a tiny electric current flowing through one part of a transistor can make a much bigger current flow through another part of it. For example, a memory chip contains hundreds of millions or even billions of transistors, each of which can be switched on or off individually. Physics 101, Handout No. 6: Notes on SOLID STATE DEVICES (MOSFET) The MOS Capacitor and MOSFET 1. The term “MOS” stands for metal-oxide semiconductor, which consists of a conductor-insulator-conductor “sandwich”. 2. A capacitor is formed when two conductors are separated by an insulator (a dielectric) across which a potential difference can exist. When the depletion region has no free charge carriers (only negative and positive ions), it can be considered as an insulator separating the n-type and p-type. This is the same as a capacitor. 3. The basic structure of a MOS capacitor is shown below. It is composed by a metal electrode called the gate, an insulator film such as silicon dioxide (SO2), and a semiconductor body called the substrate. 4. The term “MOSFET” stands for metal oxide semiconductor field effect transistor. The device is a combination of a MOS capacitor and a diode. It is the most common transistor in use. It will have three external parts: the source, the gate, and the drain. 5. The MOSFET works by electronically varying the width of a channel along which charge carriers flow. The charge carriers enter the channel at the source and exit via the drain. The width of the channel is controlled by the gate. The MOS capacitor is the main part of the MOSFET. 6. The MOSFET capacitor functions as described below: a. Two low-resistivity n-type regions (source and drain) are diffused into a high-resistivity substrate. b. The surface of the structure is covered with an insulating oxide layer and holes are cut into the layer, allowing metallic contact to source and drain. c. A metal area is overlaid on the oxide, covering the region between source and drain. Metal contacts are added to the drain and source. The metal area between the drain and source is the gate terminal. The gate terminal does not penetrate into the substrate, unlike the drain and source. d. The drain and source are like two diodes attached back-to-back. If there is no gate voltage, the current between source and drain will be very small because at least one of them will be reverse- biased for any polarity. 7. The gate acts like a capacitor (see MOS discussion). a. When a positive voltage is attached to the gate metal, it induces a negative charge on the semiconductor. b. Increasing the positive charge (voltage) will induce more negative charges until the region beneath the oxide is changed from p-type to n-type. c. Current can now flow between source and drain through the induced channel. d. Drain-current flow is moderated by the gate potential; channel resistance is inversely proportional to the gate voltage. 8. There are two types of MOSFETs: (a) depletion mode and (b) enhancement mode. Both are shown below. 9. The MOSFETs described above have the following functions: a. Depletion Type: The transistor requires the gate-source voltage to switch the device “OFF”. The depletion mode MOSFET is equivalent to a “Normally Closed” switch. b. Enhancement Type: The transistor requires a gate-source voltage to switch the device “ON”. The enhancement mode MOSFET is equivalent to a “Normally Open” switch. Integrated Circuits 10. The integrated circuit (IC), also called microelectronic circuit, microchip, or chip, is an assembly of electronic components, fabricated as a single unit, in which miniaturized active devices (e.g., transistors and diodes) and passive devices (e.g., capacitors and resistors) and their interconnections are built up on a thin substrate of semiconductor material (typically silicon). 11. The resulting circuit is thus a small monolithic “chip,” which may be as small as a few square centimetres or only a few square millimetres. The individual circuit components are generally microscopic in size. There are several basic IC types (https://www.britannica.com/technology/integrated-circuit ) : IC Type Possible Uses Analog and digital circuits Microphones, thermostat Microprocessor circuits CPU Memory circuits RAM, SSD drives Digital signal processors Voice-to-digital recording Application-specific ICs Speed controller for RC toys Radio frequency ICs Mobile phones, wireless devices Monolithic microwave ICs Radar systems, satellite communications 12. Here are diagrams of the patents applications of Jack Kilby and Robert Noyce: 13. Moore's law is the observation that the number of transistors in a dense integrated circuit doubles about every two years. Physics 101, Handout No. 7: Notes on the CMOS Inverter and Logic Circuits 1. The term CMOS stands for complementary metal oxide semiconductor. A CMOS inverter is a device that produces logic functions and is the primary component of all integrated circuits for microprocessors, microcontrollers and memory chips (RAM, ROM, and EEPROM- electrically erasable programmable ROM). 2. The CMOS inverter is a field-effect transistor that is composed of a metal gate that lies on top of an insulating layer of oxide, which lies on top of a semiconductor. Thus, it is also a MOSFET device. 3. The following are the advantages of CMOS inverters: a. Only use electricity when turned on and off, resulting in very little consumption b. Very little heat waste and are highly efficient and usable for electronic devices c. Have high noise immunity, which allows them to block frequency spikes d. Inexpensive to mass produce 4. The CMOS transistor uses both p-channel (PMOS) and n-channel (NMOS) transistors and power is dissipated in the chip only when the circuit actually switches on or off (no residual). A diagram of the CMOS transistor is shown below: 5. The NMOS is built on a p-type substrate with n-type source and drain diffused on it. The NMOS majority carriers are electrons. When a high voltage is applied to the gate, the NMOS will conduct. When a low voltage is applied to the gate, the NMOS will not conduct. NMOS are considered to be faster than PMOS because electrons travel twice as fast as holes. 6. The PMOS consists of a p-type source and drain diffused on an n-type substrate. Majority carriers are holes. When a high voltage is applied to the gate, the PMOS will not conduct. When a low voltage is applied to the gate, the PMOS will conduct. The PMOS devices are more immune to noise than NMOS devices. 7. The PMOS transistor in a CMOS inverter acts as the pull-up device because: a. It has an n-type substrate whose dominant charge carrier are electrons; electrons are more responsive than holes b. It operates on depletion mode – it will conduct when gate voltage is zero c. It has a p-type channel with holes – it means that the charge carrier current will be in the same direction as the conventional current 8. The NMOS and PMOS transistors are shown below in symbols: 9. Below is a diagram of the CMOS inverter. It consists of a PMOS and an NMOS FET: a. The input A serves as the gate voltage for both transistors b. The NMOS serves as a pull-down network between the output and the source voltage (Vss) c. The PMOS serves as a pull-up network between the output and the drain voltage (Vdd) d. The terminal Y is the output; the output is determined by the drain voltage (Vdd) e. When A has high voltage, the PMOS is OFF and the NMOS is ON. The NMOS will “pull down” the current to the Vss; thus the output is OFF. f. When A has a low voltage, the PMOS is ON and the NMOS is OFF. The PMOS will “pull up” the current to the Vdd; thus the output is ON. 10. The CMOS NAND gate and its truth table is shown below. The CMOS NAND gate is composed of two NMOS in series between Y and Vss and two PMOS in parallel between Y and Vdd: Pull-down Pull-up Network A B Network (NMOS) (PMOS) Output Y 0 0 OFF ON 1 0 1 OFF ON 1 1 0 OFF ON 1 1 1 ON OFF 0 11. The CMOS NOR gate and its truth table is shown below. The CMOS NOR gate is composed of two NMOS in parallel between Y and Vss and two PMOS in series between Y and Vdd: Pull-down Pull-up Network A B Network (NMOS) (PMOS) Output Y 0 0 OFF ON 1 0 1 ON OFF 0 1 0 ON OFF 0 1 1 ON OFF 0 Physics 101, Handout No. 8: Notes on Logical Circuits and Processors Sequential and Combinational Circuits 1. All circuits in digital devices are combinations of sequential and logical circuits. 2. Combinational circuits are made up from basic gates (AND, OR, NOT) or universal gates (NAND, NOR, or NOT) that are combined or connected together. An example of a combinational circuit is a decoder, which converts the binary code data present at its input into an equivalent decimal code at its output. The output of combinational circuits depend only on the present values of the input at a given time. 3. Sequential circuits are those whose output depends not only on the present input values but also on the previous values of the input signal. A sequential circuit can be considered to have some form of “memory” of its past history. An example of a simple sequential circuit is shown in a logic diagram below: 4. The figure below shows how a combinational circuit can be combined with a memory element to comprise a sequential circuit: 5. The differences between combinational and sequential circuits are as follows: Combinational Circuits Sequential Circuits Output depends only on the present value of Output depends on both the present and inputs previous state values of the inputs Circuits do not have memory as their outputs Circuits have some sort of memory as their change with the change in input value output changes according to previous and present values There are no feedbacks involved The outputs are connected to it as a feedback path Used in basic Boolean operations Used in the design of memory devices Used in half-adder circuit, full adder circuit, Used in RAM registers, counters, and other multiplexers, multiplexers, decoders, and state-retaining devices encoders 6. Sequential machines are used as registers. A register is a circuit that stores a single bit. In modern computers, registers can contain more than one bit (e.g. 64-bit computers have registers that are 64 bits in length). Registers hold instructions, a storage address, or any kind of data (such as bit sequence or individual characters). a. User-accessible registers – read or written by machine instructions i. Data registers – hold numeric data values ii. Address registers – used by instructions to access primary memory iii. General purpose registers – store both data and addresses iv. Status registers – hold truth values which determine instruction execution v. Floating point registers – store floating point numbers (calculation approximations) vi. Constant registers – hold read-only values such as 1, 0 or pi vii. Vector registers – hold data for vector processing done by SIMD instructions (single instruction, multiple data) viii. Special purpose registers – hold program state; usually for hardware instructions ix. Memory type range registers b. Internal registers – not accessible by instructions, used for processor operations c. Architectural register – visible to software defined by an architecture that may not correspond to the physical hardware 7. The actions of the register are synchronized by a clock. In one clock-period, the signals travel from registers at the combinational inputs through the logic circuits stored at the output registers. The number of results a machine produces per unit time is called its throughput and the time from input to output is called its latency. Computer Processors 8. A complete computer system includes: a. CPU or processor that performs computations b. Memory that stores instructions and data c. I/O devices provide input and output d. Bus interconnects all the components 9. The specifications of a processor include: a. Cores A processor core is an individual processor within a central processing unit (CPU). A multi- core processor is a single computing component with two or more independent processing units called cores, which read and execute program instructions. The instructions are ordinary CPU instructions (such as add, move data, and branch) but the single processor can run multiple instructions on separate cores at the same time, increasing overall speed for programs amenable to parallel computing. b. Clock speed Clock speed refers to the number of pulses per second generated by an oscillator that sets the tempo for the processor. Clock speed is also called clock rate, which is a measure of how fast a microprocessor executes instructions. The CPU requires a fixed number of clock cycles to execute each instruction. The faster the clock, the more instructions the CPU can execute per second. Clock speed is usually measured in megahertz or gigahertz. A higher operating frequency does not equal more performance. CPUs have a set number of instructions per clock cycle that they can process (instructions per clock, or IPC). For example, if a processor can complete one million instructions per clock cycle and each clock cycle has a frequency of 4.0 GHz, it will still not perform as well as a CPU operating at 3.7 GHz that is completing two million instructions per clock cycle. Overclocking means setting the CPU and memory to run at speeds higher that their official speed grade. Increasing the clock rate increases the number of operations per second but it also increases the rate of heat production. Overclocked computers require heat management through cooling systems to avoid damage. c. Hyper-threading Hyper-threading is a technology used by some Intel microprocessors that allows a single microprocessor to act like two separate processors to the operating system and the application programs that use it (IA-32 processor architecture). With hyper-threading, a microprocessor’s core can execute two (rather than one) concurrent streams (or threads) of instructions sent by the operating system. Having two streams of execution units to work on allows more work to be done by the processor during each clock cycle. d. Cache The processor cache is memory that store data (code, commands, etc.). It is used with the processor to facilitate the access of data from the system’s main memory or RAM. The cache reduces the average time to access memory. The processor cache consists of two levels, which are the L1 cache and the L2 cache. The L1 cache is directly accessed by the computer’s processor and holds data that the processor needs to execute instructions. The L2 cache pulls information from the system’s main memory, which is then accessed by the L1 cache. Read: https://www.extremetech.com/extreme/188776-how-l1-and-l2-cpu-caches-work- and-why-theyre-an-essential-part-of-modern-chips e. Thermal design power Thermal design power (TDP), is the maximum amount of heat generated by a computer chip or component (CPU) that the cooling system in a computer is designed to dissipate under any workload. It is an indicator of the quality of the cooling system needed to keep the CPU at an acceptable temperature. The lower the TDP of a processor, the less cooling it will need to operate at acceptable temperature levels. The higher the TDP of a CPU, the more cooling is needed. Note: The current Intel processors (Alder Lake) also now use cTPD (configurable TDP) as well as PBP (Processor Base Power) which it defines as: “the time-averaged power dissipation that the processor is validated to not exceed during manufacturing while executing an Intel- specified high complexity workload at base frequency and junction temperature as specified in the datasheet for the SKU segment and configuration.” This definition essentially tells us that the processor will “heat-crash” if you make it perform too many instructions all at once and reaches a particular temperature. Read more at: https://www.cnx- software.com/2022/01/08/tdp-vs-pbp-thermal-design-power-vs-pbp-processor-base- power-differences/