Inductor basics

Posted in Uncategorized on July 10, 2011 by brahmadath
  • It is basically constructed using a copper wire wrapped around a core make of ferromagnetic material or just around the air.When current flows through the conductor in an electric circuit, a magnetic field is generated around the conductor.
  • When the current flows through the inductor, a voltage is developed across the coil given by the formula :V = L*(dI/dt) where L is the inductance of the coil and I is current that flows through it.
  • Inductor allows dc whereas capacitor does not allow dc
  • The P.E developed across the coil is given by  E = 1/2 *L*I*I
  • Inductance is measured in  Henry.Inductors, often called reactors in power applications, are used to change the performance of the power system.
  • As the amount of inductance in an AC circuit increases, so will the amount by which the current lags the voltage.
  • An “ideal inductor” has inductance, but no resistance or capacitance, and does not dissipate or radiate energy.

Analog and Digital Circuits

Posted in Uncategorized on July 8, 2011 by brahmadath

Digital signals can only take one of two values at any one point. Analog signals, however, can take any value whithin a range.

Nowadays Digital ICs are preferred over analog circuits.

  • Reduced cost:
    Digital ICs can be programmed, meaning many different analog circuits can each be replaced with the same IC, reducing cost. For example, the same DSP chip might replace many different analog filters.
    Digital ICs can be easily expanded to put multiple functions on the same chip. For example, a DSP chip replacing multiple analog filters at the same time.
    Digital ICs can be reprogrammed without modifying the circuit, simplifying prototyping and field upgrades.
  • Increased versatility:
  • A digital IC can have its settings changed arbitrarily while it is being operated, these settings can even be changed by software. The equivalent in an analog circuit might require expensive and complicated switching techniques.
  • Numeric precision: once a signal is converted to digital data, distortion and circuit noise are no longer a significant issue. A cheap modern watch driven by a digital circuit (such as a quartz oscillator and a counter) is more precise than any analog or mechanical clock.
    Ease of storage: digital data, once recorded, does not degrade as easily as analog data.
  • Digital circuits are also becoming more prevalent where there are no analog analogues, such as computers.


Analog circuits are still more suitable for many functions. One important category is interfaces.

  • Digital circuits are usually inferior to analog circuits for receiving and transmitting signals.
  • A common digital interface, the differential line, needs an analog circuit to function well. Most digital interfaces are designed as analog, only a few legacy interfaces (which have poor performance) use entirely digital circuits.
  • Many radio signals are simply too high frequency to work with existing digital circuits. Radio modulators, demodulators, mixers, transmitters, and receivers are still analog. Some signals are even too high frequency for transistor circuits of any kind to amplify efficiently, such as microwave signals.
  • Signals must be conditioned before conversion to digital to avoid aliasing: analog filters remove unwanted parts of signals.
  • Many devices, such as monitors, require analog control. Even LCD monitors require analog circuits,
  • Audio equipment requires analog circuits. Speakers must be driven by analog signals, microphones produce analog signals.

Direct Current-Basics

Posted in Uncategorized on July 8, 2011 by brahmadath
  • Direct current  is the unidirectional flow of electric charge. This is the type of electricity that is produced by batteries, static, and lightning.
  • Direct current is produced by such sources as batteries, thermocouples, solar cells, and commutator-type electric machines of the dynamo type.
  • For virtually any type of portable or battery-powered device, you are using direct current.Also PCs use only direct current.
  • Alternating current was chosen early in the 20th century as the North American standard because it presented fewer risks and promised higher reliability than competing DC systems of the day
  • In DC circuits, the electricity is always the same polarity, which means that in a two-wire circuit, one “wire”, or side of the circuit, is always negative, and the negative side is always the one that sends the electricity.
  • There is no hum because there is no cyclic change in current flow.
  • DC current is more effective for long-distance, high-voltage transmission because it results in less energy lost in transmission, but the cost of converting DC current to AC is relatively high, so DC is typically cost-effective only for long-distance transmission.

Alternating Current(A.C)

Posted in Uncategorized on July 8, 2011 by brahmadath
  • Nikola Tesla, a Serbian-American scientist, electrical engineer, and inventor, developed the alternating-current (AC).
  • In Alternating current  the movement of electric charge periodically reverses direction. By alternating we mean change of voltage or current.
  • Usual waveform of an AC power circuit is a sine wave.AC voltage may be increased or decreased with a transformer.
  • An AC voltage v can be described mathematically as a functionof time by the following equation:  v(t)=Vpeak . sin(wt)
  • Household utility current in most countries is AC with a frequency of 60 hertz (60 complete cycles per second), although in some countries it is 50 Hz.
  • Square or sawtooth waves are produced by certain types of electronic oscillators, and by a low-end uninterruptible power supply (UPS) when it is operating from its battery.
  • The effective voltage for a sine wave is not the same as the peak voltage.

Active and Passive Devices

Posted in Uncategorized on July 8, 2011 by brahmadath

Active Devices

The components which produce the energy in the form of current or voltage are called as active components.
Example:transistors ,resistors etc.

All semiconductors are active components

Passive Devices

The components which stores the energy in the form of current or voltage are called as passive components.

Example:inductors,capacitors etc.

All non-semiconductors are passive components


Posted in Uncategorized on July 8, 2011 by brahmadath

Capacitors are passive devices used in circuits to store electrical charge for a short time.  They can be either polarised or non-polarised, which means either that they have to be connected the right way round (like the LED) or you can connect them anyway you like.. (like the resistor).

Capacitors have values that are measured in farads. Farad  is a very large unit and so more frequently capacitors have values measured in microfarads.

Capacitors were formerly known as condenser. All forms of capacitor contain at least two conductors separated by a non-conductors

Static and dynamic systems

Posted in Uncategorized on July 6, 2011 by brahmadath

Static systems

 A system whose output at time t only depends on input at time t and not any other time.

 A static system is memoryless

 All static systems are causal

Dynamic systems

Systems whose current output (at time t) depends on past inputs

Dynamics systems have MEMORY

Most engineering systems are dynamic!