0 Simple yet powerful audio amplifier

Introducing Simple Amp!

This simple yet powerful audio amplifier is an ideal DIY electronics project. Using a minimum of four parts you can build an amplifier that will put commercial sound systems to shame. Not only is this amp powerful, but it is compact, able to fit in an Altoids tin with room to spare! Check out these instructions on how to build your own.

This is the same amplifier circuit that is used to power the large 8 ohm speaker in Salvius's head. It was very important for this project to have a speaker capable of being heard across a room with clarity. Salvius is designed to be able to interact with people and the quality of sound for the robot's speech plays an important role in the ability to do so.

Detail: Simple yet powerful audio amplifier

0 The Joule Thief

This is a pretty cool device that is designed to steal every last drop of energy from a power source such as an old battery and use it to light the LED. The led I used is from a grow-light I had that got killed by a power surge. Some of the LEDs from the grow-light were still good so I used one of them. I made this joule thief a few years ago and it has been running off of a small lithium battery and a solar cell ever since. It hangs from a string in my indoor greenhouse lighting plants on the bottom shelf.

Some instructions for making your own can be found at: http://blog.makezine.com/2007/11/02/make-a-joule-thief-weeken/ #MAKE  

Detail: The Joule Thief

0 Batteries

This graphic is from a 1920's original Edison Battery manual. The 10 page manual talks about the using these cells in old vehicle applications. It is really awesome because it clearly shows the plates in the battery with spacers separating the plates. Modern batteries look terrible when cut to expose cross sections because the plates have been made so thin to increase efficiency that there isn't much to look at. I'm not complaining about the convenience of modern battery technology, but older batteries are much better for illustrating the setup of the plates.

The Edison battery is simple in how it is organized and it was revolutionary for its time. Edison was not the first to invent an battery, Alessandro Volta's development of the electrochemical cell was one of the first movements in the direction of modern battery technology. However, there is evidence that batteries may have been is use over a millennium earlier than Volta's experiments.

Somewhat of a demogorgon, the Baghdad battery is the common name for an ancient Mesopotamian artifact speculated to have been an ancient source of electric power. The battery was composed of a iron core and a copper sheet serving as the plates. The plates were sealed in a clay jar an sealed tight. It is suspected that the jar was filled with an organic acid such as fruit juice or vinegar. The supporting evidence exists, which leaves only one question, what did the ancient Mesopotamians need with a battery?

Detail: Batteries

0 Octal D Type Flip Flop DIP

I found this pack of DIP (dual inline package) chips at the fleamarket in Brimfield this weekend. They caught my eye just because the packaging looks so old. DIPs were first commercially manufactured in the 1960s but this pack was made on June 30, 1994, relatively close to the day I was born. I have never seen a pack of integrated circuits with "Flip Flop" written out on the package. Flip flop refers to a circuit with two states, the states can be changed by applying a signal to one of the control inputs. This change in the input changes the output. Flip flop logic is a fundamental part of most modern micro circuits which is why I thought it was interesting to see it here. Most ICs now have simple logic built right into them because they carry out very complicated tasks. The logic here is very important in sequential data storage because flip flops are good for storing states. 

Detail: Octal D Type Flip Flop DIP

0 Terminals and Connectors

The poster was origionaly done by http://sonic840.deviantart.com

Detail: Terminals and Connectors

0 Memristors

Memresistors are components that could be implemented to serve as memory storage devices. Currently memresistors are an imperfect technology still requiring development. Memresistors present a great advantage in data storage because they would allow great amounts of information to be stored more efficiently and would present exponentially more efficient versions of Flash, SSD, DRAM and SRAM.

Current issues exist with the physics behind the concept of memristive systems like the HP memristor seems to be in conflict with fundamentals of non-equilibrium thermodynamics. Memristors of interest have a dynamic function with memory and may be described by any of a variety of functions of net charge.

Following the dynamic state equations of such systems, one would be able to violate Landauer's principle of the minimum possible amount of energy required to change "information" states in a system. In contrast to a linear (or nonlinear) resistor the memristor has a dynamic relationship between current and voltage including a memory of past voltages or currents. As the frequency tends to infinity, the pinched hysteresis loop degenerates to a straight line through the origin, whose slope depends on the amplitude and shape of the forcing signal. In 2011 Leon Chua has argued for a broader definition so that all 2-terminal non-volatile memory devices based on resistance switching should be considered memristors.

Meuffels and R.A linear time-invariant memristor, with a constant value for M, is simply a conventional resistor.Leon Chua has more recently said that the memristor definition could be generalized to cover all forms of 2-terminal non-volatile memory devices based on resistance switching effects and Chua has said that the memristor is the oldest known circuit element with its effects predating the resistor, capacitor and inductor.Like other two-terminal components (The memristor was originally envisioned in 1971 by circuit theorist Leon Chua as a missing non-linear passive two-terminal electrical component relating electric charge and magnetic flux linkage.Since the element "remembers" the amount of current that has passed through it in the past, it was tagged by Chua with the name "memristor". When the current is stopped, the memristor retains the last resistance that it had, and when the flow of charge starts again, the resistance of the circuit will be what it was when it was last active.

Detail: Memristors

0 Solar Cells

Solar cells are made from materials that have the property known as being photovoltaic. Photovoltaic materials produce electrical current as a result of being hit by photons. The process converts light energy into electrical energy that can then be used to power electronic devices.

The Three Laws of Photovoltaics:

In order for a material to be classified as photovoltaic it must obey the following rules:

1. The absorption of light, generating either electron-hole pairs or excitons.
2. The separation of charge carriers of opposite types.
3. The separate extraction of those carriers to an external circuit.

Detail: Solar Cells

0 Phototransistors

Phototransistors operate similar to regular transistors accept that their gates are controlled by the amount of light that hits them. Depending on the phototransistor, more light can either close or open the circuit. In many ways a phototransistor is very similar to a photodiode. Both phototransistors and photodiodes are equally capable of detecting various light levels. Phototransistors however, have longer response times than photodiodes.

Phototransistors were originally developed by  Dr. John N. Shive at Bell Labs in 1948. Shive created a bipolar transistor encased within a transparent case. He used the transparent case to allow light to reach the base-collector junction of the transistor. Electrons were generated in the junction by the photons that entered it. The electrons were then injected into the base, and this photodiode current is amplified by the transistor's current gain. The creation of the phototransistor was not announced until 1950.

More information on basic transistors can be found here:

http://robotrecycled.blogspot.com/2012/07/transistors.html

Detail: Phototransistors

0 Resistors

The R is the resistance value required to provide the desired current (I) or voltage. W ratings range from as low as 1/10 W to several hundred watts. The wattage rating specifies the maximum power the resistor can dissipate without excessive heat. Resistors with higher R values usually have lower wattage ratings.The lower the power rating (W), the smaller the actual physical size of the resistor; and, conversely, the higher the power rating (W), the larger the actual physical size of the resistor.

In a wire-wound resistor, resistance wire is wrapped around an insulating core. The insulating core is usually porcelain, cement, or plain pressed paper. The wire and core are then encased in an insulating material.

!(wire wound resistor)

Carbon-composition resistors from finely divided carbon or graphite mixed with a powdered insulating material and enclosed in a plastic case for insulation and strength. The axial leads are made of tinned copper for connecting to a circuit.

!(resistor cross section)

There are two kinds of film-type resistors: carbon film-type and metal film-type. Chip resistors have a carbon coating fired onto a solid ceramic substrate. These resistors have more precise R values and greater stability with temperature changes.

The fusible resistor is a wire-wound resistor made to burn open easily when the power rating is exceeded  It serves the dual functions of a fuse and a resistor to limit current.

Resistor Color Codings

Color codes have a numeric value for each resistor.

!(resistor bands and color codes example)

The third band of a resistor indicates the decimal multiplier for the first two digits in the R value. For example, if band 1 is blue, band 2 is grey, band 3 is orange, and band 4 is silver the resistance value is 68000 Ω. For resistors under 10 Ω the third stripe is either gold or silver, indicating a fractional decimal multiplier. When the third stripe is gold, multiply the first two digits by 0.1. If the third stripe is silver, then the multiplier is 0.01. Band 4 indicates a percentage of tolerance. If the band is silver the tolerance is ± 10%. If the band is gold the tolerance is ± 5%. If there is no band for tolerance, it is ± 20%. The characteristics of a resistor can be written in the form of 45000 Ω ± 5%.

In calculating the highest ohmic value, the decimal multiplier is converted to a decimal and is multiplied by the value of the first and second bands. This product is added to the nominal ohmic value to yield the total ohmic value. For instance, if the tolerance is 5% and the nominal ohmic value is 68000 Ω then the lowest ohmic value is 64600. Wire-wound resistors are big enough physically to have the R value printed on the case. Some small wire-wound resistors are color coded with stripes. Because of economics of scale, certain sizes are in large quantity and are easily available.

Variable Resistors

!(circular carbon and slide control resistors labeled)

!(shaft, rotating arm, and soldering lugs(1, 2, 3) of circular carbon resistor labeled)

When the shaft of a circular carbon resistor is turned, the rotating arm moves closer to the soldering lugs 1 or 3. The R value changes between this terminal and the rotating arm. An example of a variable resistor at work is a light switch that allows you to control the brightness of the light.

Tapered control is the way R varies with shaft rotation on a taper. With a linear taper, one half rotation changes R by one-half the maximum value. All values of R change in direct proportion to rotation.

For a non-linear taper, R can change more gradually at one end with larger changes at the opposite end. This is accomplished by different densities of carbon on the resistance element.

Rheostats and Potentiometers

Rheostats and potentiometers are variable resistors that are either carbon or wire-wound. These resistors are used to vary the amount of current or voltage for a circuit. Rheostat resistors can be either carbon or wire-wound resistors. A rheostat is a variable R with two terminals connected in series with a load. As the rheostat's terminal fluctuates, the total resistance will reflect those changes.

!(rehostat circiut schematic)

A potentiometer is a variable voltage divider with three terminals. The purpose of a potentiometer is to provide a variable voltage between two points in a circuit. The wattage rating varies between terminals 1 and 2 and also between terminals 2 and 3. It is possible to use a potentiometer as a rheostat by connecting one of the terminals and the variable terminal.

!(potentiometer circuit schematic)

Power Rating of Resistors

A resistor should have a wattage rating high enough to dissipate the power without becoming too hot. Carbon resistors in normal operation are often quite warm with a maximum temperature of about 85 degrees Celsius. A higher wattage rating allows higher power rating. The power rating depends on the resistor construction and especially physical size. A larger physical size indicates higher temperatures. Wire-wound resistors can operate at higher temperatures. Wire-wound resistors are larger with higher wattage ratings than carbon resistors. Shelf life describes resistors accurately because they do not change with age.

Series and Parallel Combinations of Resistors

Two or more resistors may be combined to gain a desired R value. The total resistance RT depends on the series or parallel connections. However, the combination has a power rating equal to the sum of the individual resistor's value. Two equal resistors in series double the resistance for RT. For two equal resistors in parallel, the resistance is 1/2 the RT.

Resistor Troubles

The most common trouble of a resistor is an open. When a volume or tone control makes a scratchy noise as the shaft is rotated, the resistance element is worn-out. Resistance measurements are made with an ohmmeter which is pictured bellow.

!(ohmmeter)

An open resistor reads infinitely high ohms. The ohmmeter must have an ohms scale large enough to read the resistance value, otherwise the meter will read infinitely high ohms. When checking resistance in a circuit, be sure there are no parallel paths across resistors. Due to heat and time, resistors can change their in value beyond tolerance. When troubleshooting, substitute a resistor of the correct value and monitor the effects to the circuit.

Detail: Resistors

0 Relays

This picture shows an internal view of a relay. The photo was made by scanning a the relay at a resolution of 600 DPI.

Relays are often used to use a small amount of power to control devices that require larger amounts of power. Relays operate using an electromagnetic coil and a switch. When current is applied to the coil the resulting magnetic field pulls the switch closed allowing current to flow through the switch. There is no connection between the coil and the switch which means that any device that supplies the power to close the relay will not be affected by the current that passes through the switch.

Detail: Relays

0 Vacuum Tubes

Vacuum tubes can carry out a wide range of tasks similar to integrated circuits. Unlike integrated circuits, tubes have many disadvantages such as the fact that they take up a large amount of space, have shorter life spans and are less energy efficient. Tubes can control the flow of current in almost any way. They can serve as simple diodes or complex signal amplifiers. Despite the fact that they are obsolete there are qualities of tubes that some audiophiles prefer over digital alternatives when the tubes are used as audio amplifiers. Each tube produces light and heat similar to incandescent lamps because the inner part of the tube is composed of small filaments connected in different fashions to control current in different ways.

Detail: Vacuum Tubes

0 Switches

Switches are the most basic electronic component. A switch creates a break (disconnection) in a circuit to stop the flow of current. The break has almost infinite resistance because in theory it should have as much resistance as the air between the gap in the connection. Switches are said to be open when there is a gap between the contractors inside of them that disallows the flow of current. On the other hand, a switch is said to be closed when the contractors are contacting one another which enables the flow of current within the circuit. A switch is always either open or closed although some switches can have additional connections that can be closed depending on the position of the switch.

Besides the simple type of switches that are only either open or closed (on or off) there are also many other configurations that that allow a switch to select one of several circuits depending on its position.

The simplest type of switch is the single pole single throw (SPDT). The SPDT switch has two terminals that are either connected or disconnected. Another type of switch is the single pole double throw (SPDT). SPDT switches can select one of two connections to turn on. Many times these switches will be labeled with the abbreviations NC, NO, and COM; these stand for normally open (NO), normally closed (NC) and common (COM). These are the normal connections that are the default state of the switch.

Detail: Switches

0 Transformers

A transformer is a component that transfers current from one circuit to another in order to increase or decrease electrical voltage. The transfer occurs through the process of induction where electromagnetic fields induce current in a conductor.

A transformer can be broken down into three main parts: a primary winding, secondary winding, and a core. When current is applied to the primary winding the result is the production of a magnetic field. The magnetic field causes current to be produced in the secondary coil. Turn ratios are the ratio of turns in each winding. The turn ratio determines the properties of the transformer. If the primary winding has more turns than the secondary winding then the voltage is decreased. On the other hand if the primary winding has fewer turns than the secondary winding then the voltage will be increased. Transformers that increase voltage are called "step up" transformers while ones that decrease voltage are called "step down" transformers. The turn ratio can be used to calculate how much the voltage will be altered. To do this divide the number of turns on the primary winding by the number of turns on the secondary winding and multiply this by the input voltage. This will give you the output voltage of the transformer.

Detail: Transformers

0 Inductors

A inductor is an electrical component that stores energy in its magnetic field. Inductors are very simple components that are usually nothing more than a conductive material made into a coil in order to increase the magnetic field. When the current flowing through an inductor changes, creating a time-varying magnetic field inside the coil, a voltage is induced, which opposes the change in current that created it. Inductors are used in electronics where current and voltage change with time. Inductors are used to delay and reshape alternating currents.

Inductance is the property that materials have that causes current to be generated when a change occurs in the current flowing. This the result of magnetic field forming around a current-carrying conductor which tends to resist changes in the current. Electric current through the conductor creates a magnetic flux proportional to the current. A change in this current creates a corresponding change in magnetic flux which, in turn, by Faraday's law generates an electromotive force (EMF) that opposes this change in current.

Inductance is a measure of the amount of EMF generated per unit change in current. For example, an inductor with an inductance of 1 henry produces an EMF of 1 volt when the current through the inductor changes at the rate of 1 ampere per second. The number of loops, the size of each loop, and the material it is wrapped around all affect the inductance. For example, the magnetic flux linking these turns can be increased by coiling the conductor around a material with a high permeability such as iron.

- From Wikipedia

Types of Inductors:

Ideal inductors - these have inductance but no resistance or capacitance. Ideal inductors do not dissipate or radiate any sort of energy.

Real inductors -  these behave as resonant circuits because they are self-resonant.

Edit:

In an electrical circuit, resonance occurs at a particular frequency when the inductive reactance and the capacitive reactance are of equal magnitude, causing electrical energy to oscillate between the magnetic field of the inductor and the electric field of the capacitor.
Resonance occurs because the collapsing magnetic field of the inductor generates an electric current in its windings that charges the capacitor and the discharging capacitor provides an electric current that builds the magnetic field in the inductor, and the process is repeated. An analogy is a mechanical pendulum.
At resonance, the series impedance of the two elements is at a minimum and the parallel impedance is a maximum. Resonance is used for tuning and filtering, because resonance occurs at a particular frequency for given values of inductance and capacitance. Resonance can be detrimental to the operation of communications circuits by causing unwanted sustained and transient oscillations that may cause noise, signal distortion, and damage to circuit elements. - From Wikipedia

Detail: Inductors

0 Speakers

The common name for an electroacoustic transducer is 'speaker'. Speakers are simple devices that convert electrical signals into sound. Speakers are composed of three main parts; a magnet, coil and cone. There is a permanent magnet that is attached to the housing at the back of the speaker. Then a coil rests over the magnet and is attached to the cone. The cone is simply a rigid material that allows the coil to produce sound. When current passes through the coil a magnetic field is created. The magnetic field repels the permanent magnet and causes the coil to moved forward or backward rapidly. The vibration is amplified by the cone.

Detail: Speakers

0 Heatsinks

Three commonly found heatsinks and a larger one with a fan mounted on it to assist cooling.

Many integrated circuits and power regulators produce heat as they operate. The heat is the natural result of current passing through the semiconductors that they are made out of. Semiconductors have their names because they are only semiconductive and do not conduct electricity as well as some other materials. Therefore the natural resistance semiconductors have to current expends the energy of some of the electrons passing through them as heat.

Excessive heat can damage electronic devices. In order to combat the problem of heat generated in electric circuits heatsinks are sometimes attached to components that generate the most heat. Heatsinks are made of thermally conductive materials and have folds made into them in order to increase surface area so that the heat from the component is dissipated into the air quicker. Heatsinks are also sometimes attached with a layer of thermally conductive past. The paste helps to insure that heat is conducted efficiently between the component and the heatsink.

A power regulator attached to a large heatsink.

Detail: Heatsinks

0 Fuses

A fuse is a component used in electronic circuits to prevent overloads. In the event that more current is passing through a circuit that the circuit can handle or if a short occurs the fuse will break and save the rest of the circuit. This is why a fuse is sometimes referred to as sacrificial device.

Fuses work on a simple principal. When a there is a current overload the result is heat. This is because all materials, including the wire that the circuit is made of, have resistance. Resistance is the natural opposition that materials have to electric current. As electrical energy is conducted through a circuit some of the energy is consumed in the process of pushing the electrons through the material. The consumed energy is converted into heat. When a fuse blows it is because too much current was passing through it. Too much current results in an even greater amount of heat and can damage a circuit. Fuses are rated for how much current they can conduct. If more current passes through a fuse than it is rated for the fuse will heat up until the thin filament in its center blows and disconnects the circuit form the power source.

Detail: Fuses

0 Diodes

A diode is an electrical component that only allows electricity to flow in one direction. The material used to make a diode is usually a semiconductor such as silicon. The reason that a diode can block electricity in one direction and conduct it in the other is because of the p-n junction that is formed by the silicon semiconductor. The p-n junction is a boundary that is formed between a piece of p-type silicon and n-type silicon. The 'p' in the p-type semiconductor represents the fact that it is positively polarized, the same can be said for the n-type in which the 'n' indicates that the semiconductor is negative. Both the p-type and n-type semiconductors have aproximately the same level of conductivity.

The side of the diode that is connected to the p-type semiconductor is known as the anode. The anode is the negative side of any electrical device, on a diode this side is usually marked by a white line. The complete opposite can be said for the side of the diode connected to the n-type semiconductor which is known as the cathode. The cathode is the positive side of any electrical device.

Depending on the voltages of the two semiconductor regions the junction between the two semiconductors can become depleted of charge carriers. Once the carriers are depleted the semiconductor will no longer conduct electricity. This property is described as either forward bias and reverse bias. Bias in a semiconductor is the applied voltage to the p–n junction. When no current is passing through the diode the electrons in the p-n junction return to a state of equilibrium. That means that that all of the electrons return to the p-type side of the junction and all of the holes return to the n-type side. Holes are the conceptual and mathematical opposite of an electron.

Forward bias is when the positive side of the power source is connected to the anode and the negative side of the power source is connected to the cathode. The flow of current through the diode causes the p-type side to repel the holes and the n-type side to repel the electrons. This pushes the holes and the electrons close together in the center of the junction. As the holes and the electrons get closer together the electrical resistance of the n-p junction decreases thus allowing current to flow through the diode.

Reverse bias is when the negative side of the power source is connected to the cathode and the negative side of the power source is connected to the anode. The flow of current through the diode with this polarity causes the p-type side to attract the holes and the n-type side to attract the electrons. This pulls the holes and the electrons to opposite sides which depletes junction. When the junction is depleted no current can pass through.

Detail: Diodes

0 Transistors

A transistor is an electronic component that uses semiconductors to amplify and switch electronic signals and power. Transistors are composed of a semiconductor material with a minimum three terminals for connection to an external circuit. A voltage or current applied to one pair of the transistor's terminals changes the current flowing through another pair of terminals. Because the controlled (output) power can be higher than the controlling (input) power, a transistor can amplify a signal. Transistors replaced vacuum tubes and are more efficient. Today, some transistors are packaged individually as shown in the picture above, but more often they are embedded in integrated circuits.

A single model of transistor can be made in several different packaging materials which are usually made of glass, metal, ceramic, or plastic. The only thing that the package material often dictates the power rating and frequency characteristics of that particular transistor. Power transistors have larger packages with a hole so that they can be bolted to heat sinks to enable cooling.

There are two types of transistors, which have slight differences in how they are used in a circuit. A bipolar transistor has terminals labeled base, collector, and emitter. A small current at the base terminal (that is, flowing from the base to the emitter) can control or switch a much larger current between the collector and emitter terminals. For a field-effect transistor, the terminals are labeled gate, source, and drain, and a voltage at the gate can control a current between source and drain. The collector in some power transistors may be connected directly to the metal of the enclosure.

Transistors are commonly used as electronic switches, both for high-power applications such as switched-mode power supplies and for low-power applications such as logic gates. Transistors are commonly used to amplify a signal. The design of a transistor uses its common-emitter amplifier to allow a small change in voltage connected to the base of the transistor to produce a larger change in the output of the transistor.



There are many different types of transistors and most look virtually the same making it impossible to tell the difference between two types without looking them up. The two most common types of transistors are NPN and PNP. These two types represent the two basic types of setups for transistors.

In a PNP transistor, the current passes through the emitter before it reaches the base, and the current leaving the base passes through the collector; for example, "emitter-base-collector." PNP is an acronym for the polarity of the transistor; the emitter is positive, the base is negative, and the collector is positive. The majority current carrier in a PNP transistor are holes, or a lack of electrons, rather than electrons.

In a NPN transistor, the emitter and collector reverse roles, so the current passes through the collector before reaching the base and leaves through the emitter; for example, "collector-base-emitter." An NPN transistor's polarity is negative-positive-negative, and the majority current carriers are electrons instead of holes. Because NPN and PNP have opposite charges, the battery's bias, or polarity powering the transistor, is reversed.


The labeling methods for transistors can sometimes be inconsistent but there is a general rule for naming them that can be used to find out more about a transistor based on the information provided on its label.

The types of some transistors can be determined based on the information provided in the label. There are three major semiconductor labeling standards. In each standard there is an alphanumeric prefix that provides clues to type of the device. The three labeling standards are include the Japanese Industrial Standard, Pro Electron Standard, and the JEDEC EIA370 Standard. There are also other naming conventions that are standard to specific companies which only adds to the confusion and may not always provide a reliable source of determining the transistor's identity. These issues that occur in manufacturing labels are only added to when yo consider how some transistors have duplicate labels such as the J176 low-power Junction FET and the higher-powered MOSFET 2SJ176 (both of which are labeled J176).

The first category of transistors is based on the date that the type of semiconductor material was first used to make transistors. The

metalloid germanium (1947) and silicon (1954)— in amorphous, polycrystalline and monocrystalline form; the compounds gallium arsenide (1966) and silicon carbide (1997), the alloy silicon-germanium (1989), the allotrope of carbon graphene (research ongoing since 2004), etc.

The other categories are as follows:

The Second category is structure: BJT, JFET, IGFET (MOSFET), IGBT, and "other types"

Electrical polarity (positive and negative) : NPN, PNP (BJTs); N-channel, P-channel (FETs)

Maximum power rating: low, medium, high

Maximum operating frequency: low, medium, high, radio frequency (RF), microwave (The maximum effective frequency of a transistor is denoted by the term fT, an abbreviation for transition frequency—the frequency of transition is the frequency at which the transistor yields unity gain)

Application: switch, general purpose, audio, high voltage, super-beta, matched pair

Physical packaging: through-hole metal, through-hole plastic, surface mount, ball grid array, power modules.

Amplification factor hfe or βF (transistor beta).

Using this classification taxonomy a particular transistor can be described as something along the lines of: silicon, surface mount, BJT, NPN, low power, high frequency switch.

Types of transistors: (including some more unusual types)

• Bipolar junction transistor 
• Heterojunction bipolar transistor 
• Schottky transistor 
• Avalanche transistor 
• Darlington transistor 
• Insulated gate bipolar transistor 
• Photo transistor 
• Multiple-emitter transistor 
• Multiple-base transistor 
• Field-effect transistor 
• Carbon nanotube field-effect transistor (CNFET) 
• Junction gate field-effect transistor (JFET) 
• Metal semiconductor field effect transistor (MESFET) 
• High Electron Mobility Transistor (HEMT, HFET, MODFET) 
• Metal–oxide–semiconductor field-effect transistor (MOSFET) 
• Inverted-T field effect transistor (ITFET) 
• Fin field-effect-transistors (FinFET) 
• Fast-recovery epitaxial diode field-effect transistor (FREDFET) 
• Thin film transistor 
• Organic field-effect transistor (OFET) 
• Ballistic transistor 
• Floating-gate transistor 
• Field-effect transistor (FET) 
• Ion-sensitive field effect transistor 
• Electrolyte-oxide-semiconductor field effect transistor (EOSFET) 
• Deoxyribonucleic acid field-effect transistor (DNAFET) 
• Diffusion transistor 
• Unijunction transistors 
• Single-electron transistors (SET) 
• Nanofluidic transistor 
• Multigate transistors 
• Tetrode transistor 
• Pentode transistor 
• Trigate transistors 
• Dual gate FETs 
• Junctionless Nanowire Transistor (JNT) 

Resources: What Is a PNP Transistor? | eHow.com http://www.ehow.com/info_10026494_pnp-transistor.html#ixzz21B92sdPW, http://en.wikipedia.org/wiki/Transistor

Detail: Transistors

0 Piezoelectricity

Piezoelectricity is the property of various materials to either generate an electricity when mechanical stress is applied. These materials can also function by doing the opposite, they can generate mechanical power when voltage is applied. Until mechanical stress or electrical power is applied to the material it remains overall electrically neutral.

Piezoelectric materials can generate astounding amounts of voltage. For instance, if you properly apply mechanical stress to a 1 cm cube of quartz with 2 kN (500 lbf) of correctly applied force can produce a voltage of 12,500 V.

The piezoelectric property commonly is found in materials with a crystalline structure. This is because the structure of the crystal contains positive and negative electrical charges; each separated from the next but placed at symmetric locations throughout the crystal. Each side of the crystal structure forms an electric dipole. Dipoles are pairs of equal and oppositely charged or poles separated by a distance. When dipoles are near each other they tend to be aligned in regions called Weiss domains. The domains are usually randomly oriented, but can be aligned during a process by which a strong electric field is applied across the material. This process is called poling. Poling is usually at elevated temperatures. There is also a process called poling that is referred to when polarizing permanent magnets but the only relation that the two terms have is the meaning that they are creating polarities of some sort within a material.Spatially separated charges result in an electric field. This means that in a piezoelectric material there will always be an electric potential.

Some commonly used piezoelectric materials are listed bellow. All of these are either naturally occurring or man-made.

• cane sugar
• quartz
• berlinite
• Rochelle salt
• topaz
• tourmaline
• Dry bone
• Tendon
• Silk
• Wood due to piezoelectric texture
• Enamel
• Dentin
• gallium orthophosphate (GaPO4)
• Langasite (La3Ga5SiO14)
• Man-made ceramics
• Tetragonal unit cell of lead titanate
• barium titanate (BaTiO3)
• lead titanate (PbTiO3)
• lead zirconate titanate (Pb[ZrxTi1-x]O3 0<x<1)
• potassium niobate (KNbO3)
• lithium niobate (LiNbO3)
• lithium tantalate (LiTaO3)
• sodium tungstate (Na2WO3)
• Ba2NaNb5O5
• Pb2KNb5O15
• Polyvinylidene fluoride (PVDF)
• Lead-free piezoceramics
• Bismuth ferrite (BiFeO3)

Application of piezoelectric materials:

Electric cigarette lighters, gas grill and stove igniters use piezoelectric piezoelectric crystal to ignite a flammable gas. When you press a button a hammer to hits a chunk of some sore of piezoelectric. This generates a high enough voltage to allow electric current to jump across a small spark gap. This heats and ignites the gas.

Photo by Anthony

Piezoelectrics are also commonly used for detecting sound such as in piezoelectric microphones. When sound waves hit the material it distorts and produces an electric signal. The term transducer is sometimes used when the device both sends and detects mechanical force. This is usually used in ultrasonic sensors which emit a sound and then detect the vibration when it bounces off a surface.

Detail: Piezoelectricity