Monday, December 02, 2013
Saturday, November 30, 2013
Monday, October 21, 2013
- At room temperature, Silicon crystal has fewer free electrons than Germanium crystal. This implies that silicon will have much smaller Collector cut off current than Germanium.
- The variation of Collector cut off current with temperature is less in Silicon compared to Germanium.
- The structure of Germanium crystals will be destroyed at higher temperature. However, Silicon crystals are not easily damaged by excess heat.
- Peak Inverse Voltage ratings of Silicon diodes are greater than Germanium diodes.
- Si is less expensive due to the greater abundance of element. The major raw material for Si wafer fabrication is sand and there is lots of sand available in nature.
Sunday, March 17, 2013
How MRI works
Thursday, February 14, 2013
This gives the Darlington pair a very high current gain such as 10000.
Darlington pairs are sold as complete packages containing the two transistors.
They have three leads (B, C and E) which are equivalent to the leads of a standard individual transistor.
- TTL circuits utilize BJTs while CMOS circuits utilize FETs.
- CMOS allows a much higher density of logic functions in a single chip compared to TTL.
- TTL circuits consumes more power compared to CMOS circuits at rest.
- CMOS chips are a lot more susceptible to static discharge compared to TTL chips
- Propagation delay is more in CMOS compared to TTL
- Switching Speed is More for TTL compared to CMOS.
- CMOS devices are cheaper than TTL Devices.
- The Power Supply requirement for TTL is 3 to 15V, small fluctuations are tolerated.
- The Power Supply requirement for CMOS is 5V ±0.25V, it must be very smooth, a regulated supply.
- TTL Can handle only less frequency compared to CMOS.
Since TTL has very little parasitic capacitance, the time delay is very small, & TTL is faster.
MOSFETs, based on voltage operations, have much greater capacitances, the charging & discharging of which consumes time (Ref: RC time constant), hence CMOS is slower.
In Digital Designs, our primary aim is to create an Integrated Circuit (IC).
- Supply voltage range
- Speed of response
- Power dissipation
- Input and output logic levels
- Current sourcing and sinking capability
- Noise margin
- Bipolar Devices
- MOS Devices
- Hybrid Devices
- Diode Logic (DL)
- Resistor Transistor Logic (RTL)
- Diode Transistor Logic (DTL)
- Transistor- Transistor Logic (TTL)
- Emitter Coupled Logic (ECL) or Current Mode Logic (CML)
- Integrated Injection Logic (IIL)
- P-MOS Family
- N-MOS Family
- Complementary-MOS Family
- Standard C-MOS
- Clocked C-MOS
- Pseudo N-MOS
- C-MOS Domino Logic
- Pass Transistor Logic
- Bi-CMOS Family
- Diode Logic suffers from voltage degradation from one stage to the next.
- Diode Logic only permits OR and AND functions.
In RTL (resistor transistor logic), all the logic are implemented using resistors and transistors. One basic thing about the transistor (NPN), is that HIGH at input causes output to be LOW (i.e. like a inverter). In the case of PNP transistor, the LOW at input causes output to be HIGH.
- Less number of Transistors
- High Power Dissipation
- Low Fan In
In DTL (Diode transistor logic), all the logic is implemented using diodes and transistors.
- Propagation Delay is Larger
In Transistor Transistor logic or just TTL, logic gates are built only around transistors.
TTL Logic has the following sub-families:
- Standard TTL.
- High Speed TTL
- Low Power TTL.
- Schhottky TTL.
- Low Power Schottky TTL
- Advanced Schottky TTL
- Advanced Low Power Schottky TTL
- Fast Schottky
The main specialty of ECL is that it is operating in Active Region than the Saturation Region. That is the reason for its high speed operation. As you can see in the figure, the Emitters of the Transistors Q1 and Q2 are coupled together.
|Emitter Coupled Pair|
- Large Silicon Area
- Large Power Consumption
Monday, February 11, 2013
DTS (Digital Theater Sound) is a digital sound coding standard created by Universal. Compared with the Dolby Digital standard, DTS uses four times less compression and digitises sound at 20 bits instead of 16. Therefore, DTS's sound quality is theoretically higher, at the cost of a higher bit rate. To be able to play DTS-encoded media, you need a certified DTS decoder.
DTS falls into four different categories:
• DTS 6, the most commonly used 5.1 standard, which can encode six-channel sound with less compression than the Dolby Digital standard. The first five channels are used for the satellite speakers, while the last is reserved for the subwoofer. These devices are normally identified by the presence of this logo:
o DTS ES Matrix, which has a seventh channel interpolated with the primary channels. This is called "virtualisation".
o DTS ES Discrete has an seventh independent channel.
• DTS 24/96 represents an audio format used for storing high-definition music with several channels. This format is primarily used in DVD Audio, or audio tracks which accompany video DVDs. The name comes from the fact that the tracks are recorded in 24 bits at 96 kHz. It may be in either stereo or 5.1.
They both use the 5.1 speaker format The format consists of three speakers across the front and two speakers in the rear. The .1 is a sixth channel called an LFE that is sent to a subwoofer.Dolby Digital uses the AC-3 file format, which any Dolby Digital Decoder can decoder to produce 5.1 audio. Dolby Digitalis the technical name for Dolby's multi-channel digital sound coding technique, more commonly referred to as Dolby 5.1.
A six-channel sound coding process (one channel each for front, left, center, right surround, left surround and a sub-woofer) originally created by Dolby for theaters, AC-3 was subsequently adapted for home use and is now steadily becoming the most common sound format for DVD.
The difference between Dolby Digital (AC-3) and DTS is:
Both systems are great but statistics for reference only..
• DTS seems to provide a deeper and tighter low frequency presence
• DTS allows the sound to breath - transparency
• AC-3 seems to leave the impression that something is missing from the mix.
• At lower bit-rates AC-3 starts to sound like MP3's encoded at 96kbps (artifacts)
Sunday, February 10, 2013
In this manner, a violin makes a sound when the bow makes its strikes vibrate, and a piano sounds a note when a key is struck, because a hammer struck a string and made it vibrate.
Speakers are generally used to reproduce these sounds. They are a membrane connected to an electromagnet; as an electrical current travels in front of and behind the magnet very rapidly, it causes vibrations in the air in front of it, and that vibration is sound! This is how sound waves are produced; they can be represented in a diagram as changes in air pressure (or in the electricity level of the magnet) as a function of time.
A sonogram, on the other hand, depicts sound frequencies as a function of time. It should be noted that a sonogram shows fundamental frequency, on top of which higher frequencies, called harmonics, are superimposed. This is what allows us to distinguish between different sources of sound: low notes have low frequencies, while high notes have higher frequencies.
Sampling rate -Sound quality
• 32 kHz: for digital FM radio (band-limited to 15 kHz)
• 44.1 kHz: for professional audio and compact discs • 48 kHz: for professional digital multitrack recording, and consumer recording equipment (like DAT or MiniDisc)
A computer works with bits, so the number of possible values that the sample could have must be determined. This is done by setting the number of bits on which the sample values are encoded.
• With 8-bit coding, there are 28 (= 256) possible values.
• The sampling rate
• The number of bits in a sample
• The number of channels (one for mono, two for stereo, and four for quadrophonic sound
Saturday, February 09, 2013
Placing P-type semiconductor between two N-type semiconductor is NPN transistor
It operates by a small current flow from the emitter to base.current will not flow from the emitter to the collector until a small voltage (at least 0.7 volts) is applied to the base.
Collector current is much larger than the base current.
Placing N-type semiconductor between two P-type semiconductor is PNP transistor.
Its operation is same as NPN but reversed.The voltage relations also reversed.So to turn on the device both the collector and base must be negative.
When the base voltage is about 0.85 volts, sufficient base current flows to turn the transistor fully on. The collector voltage drops to approximately half a volt because of the voltage drop across the collector resistor. A transistor which is conducting the maximum current is said to be in saturation.
Friday, February 08, 2013
|P Type and N Type Materials- Before forming the Junction|
|P and N type Materials Brought together|
|Recombination Started (Gold Balls- Recombination)|
|Depletion Region Formed|
(From the article: 'Education in Three Dimensions: Using Virtual Reality in Education for Illustrating Spatial Relationships' by ALLPORT, Christopher, SINES, Paul, SCHREINER, Brandon & DAS, Biswajit)
MEMS is an emerging technology in which Microscopic Machines are developed by the tools and techniques that were developed for the Integrated Circuit (IC)ndustry.
|Components of MEMS|
|SMART BIOMEM (LAB ON A CHIP)|
This technology has an enormous number of application areas, including
- Automotive Eg. Accelerometers for airbag systems, Roll-over detection systems, etc.
- Biomedical Eg.Neural prosthesis devices like hearing and visual aids, Smart drug delivery systems, On Chip body fluid analysis systems, Microsurgery tools, Pacemakers
- Telecommunication Eg. Micromirrors for fiber optic switching for fast internet,Smart Antennas
- Household appliances pressure sensors for water level detection, frost sensors for refrigerators
- Consumer Applications DLP projectors, i-phone,
- Defense applications Eg. Low cost night vision, Smart munitions
Sunday, February 03, 2013
Wednesday, January 30, 2013
When the current flows in a given direction, a magnetic field is produced whose polarity points into the ground; when the current flow is reversed, the field's polarity points out of the ground. Any metallic object which happens to be nearby will have a flow of current induced inside of it by the influence of the changing magnetic field, in much the same way that an electric generator produces electricity by moving a coil of wire inside a fixed magnetic field. This current flow inside a metal object in turn produces its own magnetic field, with a polarity that tends to be pointed opposite to the transmit field.
The resulting received signal will usually appear delayed when compared to the transmitted signal. This delay is due to the tendency of conductors to impede the flow of current (resistance) and to impede changes in the flow of current (inductance). We call this apparent delay "phase shift". The largest phase shift will occur for metal objects which are primarily inductive; large, thick objects made from excellent conductors like gold, silver, and copper. Smaller phase shifts are typical for objects which are primarily resistive; smaller, thinner objects, or those composed of less conductive materials.
Tuesday, January 08, 2013
Wire JumperA wire jumper is a small piece of uninsulated wire that is place in two adjacent PCB holes and soldered into position based on our requirement.It is called jumper because,The wire jumps the electrical signal or power from one pcb hole to another.
Standard Wire Jumper
Thursday, December 20, 2012
Twin-T Band-stop filter
Hardwork Can Never Ever Fails...
1. Capacitive band-pass filter.
2.Inductive band-pass filter.
Hardwork Can Never Ever Fails...
1.Capacitive high-pass filter.
The response of the capacitive high-pass filter increases with frequency.
2.Inductive high-pass filter.
The capacitive design is the simplest since it requires only one component above and below the load.And, again, the reactive purity of capacitors over inductors tends to favor their use in filter design, especially with high-pass filters where high frequencies commonly cause inductors to behave strangely due to the skin effect and electromagnetic core losses.
Hardwork Can Never Ever Fails...
Wednesday, December 19, 2012
1.Capacitive low-pass filter
The capacitor's impedance decreases with increasing frequency. This low impedance in parallel with the load resistance tends to short out high-frequency signals.It drops most of the voltage across series resistor R1
2.Inductive low-pass filter
The inductor's impedance increases with increasing frequency. This high impedance in series tends to block high-frequency signals from getting to the load.
In this case,the inductive low-pass filter is very simple in structure. The capacitive version of this filter is not that much more complex, with only a resistor and capacitor needed for operation. Due to its complexity, capacitive filter designs are generally preferred over inductive because capacitors tend to be “purer” reactive components than inductors and therefore are more predictable in their behavior. By “pure” I mean that capacitors exhibit little resistive effects than inductors, making them almost 100% reactive. Inductors, on the other hand, typically exhibit significant dissipative (resistor-like) effects, both in the long lengths of wire used to make them, and in the magnetic losses of the core material. Capacitors also tend to participate less in “coupling” effects with other components than inductors, and are less expensive.
Hardwork Can Never Ever Fails...
A tweeter (high-frequency speaker) is inefficient at reproducing low-frequency signals such as drum beats, so a crossover circuit is connected between the tweeter and the stereo's output terminals to block low-frequency signals, only passing high-frequency signals to the speaker's connection terminals. This gives better audio system efficiency and thus better performance. Both equalizers and crossover networks are examples of filters, designed to accomplish filtering of certain frequencies.
Hardwork Can Never Ever Fails....
Inside a piezoelectric version, the sensing element is a crystal which has the property of emitting a charge when subjected to a compressive force.
In the accelerometer, this crystal is bonded to a mass such that when the accelerometer is subjected to a 'g' force, the mass compresses the crystal which emits a signal. This signal value can be related to the imposed 'g' force.
The sensing element is housed in a suitable sensor body to withstand the environmental conditions of the particular application. Body are usually made in stainless steel with welding of the various parts to prevent the ingress of dust, water, etc.
Electrical connection can be via a sealed cable or a plug/socket arrangement.
Many present accelerometers have internal electronic circuitry to give outputs which can be directed used by the associated acquisition or control systems.
Mechanical fixing of the sensor is important in order to achieve true transfer of the vibration or acceleration. Many fixing methods are used including beeswax, hard glues, threaded stud (male or female), magnetic mounts.
Accelerometers are used in many scientific and industrial applications such as predictive maintenance, aerospace, automotive, medical, process control, etc.
Alternating Current (AC)
Alternating current (AC) electricity is the type of electricity commonly used in homes and businesses throughout the world. While direct current (DC) electricity flows in one direction through a wire, AC electricity alternates its direction in a back-and-forth motion. The direction alternates between 50 and 60 times per second, depending on the electrical system of the country.
AC electricity is created by an AC electric generator, which determines the frequency. What is special about AC electricity is that the voltage can be readily changed, thus making it more suitable for long-distance transmission than DC electricity. But also, AC can employ capacitors and inductors in electronic circuitry, allowing for a wide range of applications.
Direct Current (DC) Electricity.
Direct current or DC electricity is the continuous movement of electrons from an area of negative (−) charges to an area of positive (+) charges through a conducting material such as a metal wire. Whereas static electricity sparks consist of the sudden movement of electrons from a negative to positive surface, DC electricity is the continuous movement of the electrons through a wire.
A DC circuit is necessary to allow the current or steam of electrons to flow. Such a circuit consists of a source of electrical energy (such as a battery) and a conducting wire running from the positive end of the source to the negative terminal. Electrical devices may be included in the circuit. DC electricity in a circuit consists of voltage, current and resistance. The flow of DC electricity is similar to the flow of water through a hose.
Difference between AC and DC electricity
Electrons have negative (−) electrical charges. Since opposite charges attract, they will move toward an area consisting of positive (+) charges. This movement is made easier in an electrical conductor, such as a metal wire.
Electrons move direct with DC electricity
With DC electricity, connecting a wire from the negative (−) terminal of a battery to the positive (+) terminal will cause the negative charged electrons to rush through the wire toward the positive charged side. The same thing happens with a DC generator, where the motion of coiled wire through a magnetic field pushes electrons out of one terminal and attracts electrons to the other terminal.
Electrons alternate directions in AC electricity
With an AC generator, a slightly different configuration alternates the push and pull of each generator terminal. Thus the electricity in the wire moves in one direction for a short while and then reverses its direction when the generator armature is in a different position.
AC movement of electrons in wire
The charge at the ends of the wire alternates between negative (−) and positive (+). If the charge is negative (−), that pushes the negatively charged electrons away from that terminal. If the charge is positive (+), the electrons are attracted in that direction.
Rate of change
AC electricity alternates back-and-forth in direction 50 or 60 times per second, according to the electrical system in the country. This is called the frequency and is designated as either 50 Hertz (50Hz) or 60 Hertz (60Hz).
Light bulbs in Both AC and DC
Many electrical devices—like light bulbs—only require that the electrons move. They don't care if the electrons flow through the wire or simply move back-and-forth. Thus a light bulb can be used with either AC or DC electricity.