Monday, May 14, 2012

ROM Addressing Animation

Here the corresponding memory cell is activated using the Switching Mechanism.
The Value stored in the Cell is given as the Output.
Even though the actual mechanism of ROM is slightly different from this, this animation is useful to understand the memory addressing concept.
The Output D0-D7 represents the value store in the cell addressed by the input.

How Johnson Counter Works? Animation

Johnson Counter with Timing diagram

A Johnson counter is a modified ring counter, where the output from the last stage is inverted and fedback as input to the first stage. A pattern of bits equal in length to twice the length of the shift registerthus circulates indefinitely. These counters find specialist applications, including those similar to the decade counter, digital to analog conversion, etc. it can be established by D flip flop and JK flip flop.

How JFET works? Animation

Please Click Here to view the interactive Flash Animation of JFET working.

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Sunday, May 13, 2012

Rectifier- Basics

What is Rectifier?
               A rectifier is a device that simply converts alternating current (AC) into direct current (DC).  
             The way a rectifier changes AC to DC is by the use of a diode, or multiple diodes.  Diodes only allow electrons to flow in one direction through them.
   When the voltage on the anode is more positive than the voltage on the cathode, current will flow through the diode.  If the voltage is reversed, making the cathode more positive, then current will not flow through the diode.  (unless the peak reverse voltage rating is exceeded).

Types of Diode :

1) Halfwave Rectifier

On the first half of the cycle the diode allows the electrons to flow through it powering the DC load.  On the second half cycle the diode blocks the flow of electrons and the load receives no flow at all.  This is what causes the flicker effect of cheap LED lights.

 2) Full wave Bridge Rectifier

On the first half of our cycle the flow electrons passes through the bridge allowing electrons to 
flow to the load in one direction.  Then on the second half of the cycle the flows passes through the bridge recifier following a different path, but still sends the electron flow in the same direction to the load giving it twice the output of a single diode rectifier.  In the animation above, the cycles are moving at 1/16 cycle per second, while in actuality, this is happening 960 times faster at 60 cycles per second.  An RC filter (a resistor and a capacitor wired in parallel with the DC load) further smooths the output reducing the flicker even more.  So to answer our original question, LED Christmas lights that make use of full-wave bridge rectifier technology are worth spending  a little more for.




Saturday, May 12, 2012

Positive and Negative Feedback

Negative Feedback

                          If we connect the output of an op-amp to its inverting input and apply a voltage signal to the noninverting input, we find that the output voltage of the op-amp closely follows that input voltage.
                          As Vin increases, Vout will increase in accordance with the differential gain. However, as Vout increases, that output voltage is fed back to the inverting input, thereby acting to decrease the voltage differential between inputs, which acts to bring the output down.

What will happen for any given voltage input is that the op-amp will output a voltage very nearly equal to Vin, but just low enough so that there's enough voltage difference left between Vin and the (-) input to be amplified to generate the output voltage?
            The circuit will quickly reach a point of stability (known as equilibrium in physics), where the output voltage is just the right amount to maintain the right amount of differential, which in turn produces the right amount of output voltage. Taking the op-amp's output voltage and coupling it to the inverting input is a technique known as negative feedback, and it is the key to having a self-stabilizing system.

Positive Feedback

                  Unlike negative feedback, where the output voltage is "fed back" to the inverting (-) input, with positive feedback the output voltage is somehow routed back to the noninverting (+) input.
                  The inverting input remains disconnected from the feedback loop, and is free to receive an external voltage.

Hardwork Never Ever Fails

Good Luck...

Friday, May 11, 2012

Animation of operational amplifier

Here you have the fantastic animation of operational amplifier...

Never miss this friends...



Binary Adder Animations

Please Click Here to view a beautiful animation of Binary Adders.

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Half Adder Animation

The half adder is an example of a simple, functional digital circuit built from two logic gates.  The half adder adds to one-bit binary numbers (AB).  The output is the sum of the two bits (S) and the carry (C). Note how the same two inputs are directed to two different gates.  The inputs to the XOR gate are also the inputs to the AND gate.  The input "wires" to the XOR gate are tied to the input wires of the AND gate; thus, when voltage is applied to the A input of the XOR gate, the A input to the AND gate receives the same voltage.


 MEMRISTOR:(a future memory device)

FIG:memristor symbol
What is a memristor? Memristors are basically a fourth class of electrical circuit, joining the resistor, the capacitor, and the inductor, that exhibit their unique properties primarily at the nanoscale. Theoretically, Memristors, a concatenation of “memory resistors”, are a type of passive circuit elements that maintain a relationship between the time integrals of current and voltage across a two terminal element. Thus, a memristors resistance varies according to a devices memristance function, allowing, via tiny read charges, access to a “history” of applied voltage. The material implementation of memristive effects can be determined in part by the presence of hysteresis (an accelerating rate of change as an object moves from one state to another) which, like many other non-linear “anomalies” in contemporary circuit theory, turns out to be less an anomaly than a fundamental property of passive circuitry.
Until recently, when HP Labs under Stanley Williams developed the first stable prototype, memristance as a property of a known material was nearly nonexistant. The memristance effect at non-nanoscale distances is dwarfed by other electronic and field effects, until scales and materials that are nanometers in size are utilized. At the nanoscale, such properties have even been observed in action prior to the HP Lab prototypes.
But beyond the physics of electrical engineering, they are a reconceptualizing of passive electronic circuit theory first proposed in 1971 by the nonlinear circuit theorist Leon Chua. What Leon Chua, a UC Berkeley Professor, contended in his 1971 paper Transactions on Circuit Theory, is that the fundamental relationship in passive circuitry was not between voltage and charge as assumed, but between changes-in-voltage, or flux, and charge. Chua has stated: “The situation is analogous to what is called “Aristotle’s Law of Motion, which was wrong, because he said that force must be proportional to velocity. That misled people for 2000 years until Newton came along and pointed out that Aristotle was using the wrong variables. Newton said that force is proportional to acceleration–the change in velocity. This is exactly the situation with electronic circuit theory today. All electronic textbooks have been teaching using the wrong variables–voltage and charge–explaining away inaccuracies as anomalies. What they should have been teaching is the relationship between changes in voltage, or flux, and charge.”
As memristors develop, its going to come down to, in part, who can come up with the best material implementation. Currently IBM, Hewlett Packard, HRL, Samsung and many other research labs seem to be hovering around the titanium dioxide memristor, but there are quite a few other types of memristors with vectors of inquiry.

Thursday, May 10, 2012

Basic Concept in Oscillator


It produces a repetitive electronic signal, often a sine wave or a square wave.Oscillators are often characterized by the frequency of their output signal. An audio oscillator produces frequencies in the audio range, about 16 Hz to 20 kHz. An RF oscillator produces signals in the radio frequency (RF) range of about 100 kHz to 100 GHz. A low-frequency oscillator (LFO) is an electronic oscillator that generates a frequency below ≈20 Hz.

Oscillation Basics

One of the most commonly used oscillators is the pendulum of a clock. If you push on a pendulum to start it swinging, it will oscillate at some frequency -- it will swing back and forth a certain number of times per second. The length of the pendulum is the main thing that controls the frequency.
For something to oscillate, energy needs to move back and forth between two forms. For example, in a pendulum, energy moves between potential energy and kinetic energy. When the pendulum is at one end of its travel, its energy is all potential energy and it is ready to fall. When the pendulum is in the middle of its cycle, all of its potential energy turns into kinetic energy and the pendulum is moving as fast as it can. As the pendulum moves toward the other end of its swing, all the kinetic energy turns back into potential energy. This movement of energy between the two forms is what causes the oscillation.
Eventually, any physical oscillator stops moving because of friction. To keep it going, you have to add a little bit of energy on each cycle. In a pendulum clock, the energy that keeps the pendulum moving comes from the spring. The pendulum gets a little push on each stroke to make up for the energy it loses to friction.

The Block diagram of oscillator is shown below


The working of amplifier and positive feedback will be posted soon... 



Animation of D Flip Flop

D Flip FLop

D Flip flop is generally called the Data Flip Flop. It will also called Delay Flip Flop.

It will just pass the data given into the input to the output. The data will move from the input to output only if the Clock Signal is high.

The NAND realization of D Flip Flop is given below.

D Flip Flop using NAND Gates

The Truth Table of D Flip flop is shown below.

D Flip Flop Truth Table

How an SR Flip Flop worlks?

An SR Flip-Flop can be considered as a basic one-bit memory device that has two inputs, one which will "SET" the device and another which will "RESET" the device back to its original state and an output Q that will be either at a logic level "1" or logic "0" depending upon this Set/Reset condition. A basic NAND Gate SR flip flop circuit provides feedback from its outputs to its inputs and is commonly used in memory circuits to store data bits. The term "Flip-flop" relates to the actual operation of the device, as it can be "Flipped" into one logic state or "Flopped" back into another.

The Animation of the SR Flip Flop using NOR gate is shown below.

SR Flip Flop NOR Realization

The Block Diagram, NAND Realization and Truth Table are given below.


How an Electric Bell Works?

In Electric Bells, a coil is wounded on an Iron core.
When current passes through this coil, the Iron core will act as an Electro Magnet.
It will attract the spring loaded Arm with a clapper on its end to the Bell.

You can see the animation below.

B- Bell, E-Electro Magnet, K-Switch, U-Power Source, A-Clapper Arm, T-Electric Contact

Electric Bell


How the Telephone Multiplexer works?

We know that related to a Telephone Exchange, there are lot of subscribers.
How the Exchange is sharing the bandwidth for all the subscribers??

There are lot of multiplexing methods like FDMA, TDMA and CDMA.

In our Telephone Exchanges actually they are using the Time Division Multiple Access Scheme.

Here you can view the animation about the Working of the TDMA.

TDMA in Telephone Exchange

Saturday, May 05, 2012


ANS:   Bipolar transistors can have both minority and majority carriers flowing, whereas FET's only have majority carriers flowing. The fact that bipolar transistors have two types of carriers flowing simultaneously results in the name 'bi-polar'. The minority carrier flow is responsible for collector conduction modulation and transistor storage time.

QUES: Why is a bipolar transistor current driven?
ANS  : A bipolar transistor has the base electrically connected and needs base current to turn on.
QUES:What does the SOA define ?
ANS  :The SOA (Safe Operating Area) defines the permissible region of operation for linear applications. The circuit designer must make sure the transistor is never used outside the SOA boundaries.

QUES:Can the base be driven negatively ?
ANS  :Yes, but there is a maximum level that should not be exceeded. The maximum negative base-emitter voltage can be found in the maximum ratings table. Exceeding this value will not immediately destroy the transistor if base current is held to a moderate value, but repeated avalanche base-emitter reverse breakdown may lead to shifts of dopants altering the characteristics of the transistor.

QUES:What is fT ?
ANS  : The transistion frequency is where the current gain of the BJT is reduced to unity. This means that it is the highest frequency at which there is amplifying action. Practical circuits will use the transistor at frequencies well below fT.

Thursday, May 03, 2012

Basic Science- Mathematics animations

Please Click Here to see some basic Animations on Science and Mathematics.
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I recommend everyone to go through it atleast once for a better understading of what you have studied already.


LCR Animation

The behavior of Capacitor, Resistor and Inductor in an AC circuit and DC circuit will create confusion in most of the students.

Please Click Here to see a Fantastic animation of the same. There you can Change the Resistor, Capacitor, Inductor, Phase, Frequency etc.


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Basics of Inductors

An inductor is a coil of wire either hollow, or wound around some ferrous (magnetic) material.
When current flows through the coil a magnetic field is produced. When the current stops flowing the magnetic field collapses.
If the coil is connected to a d.c. supply, a steady current will flow, and the opposition to the flow will be mainly due to the resistance of the wire used to make the coil.

inductor basics
Inductor Coil

However, at the moment when the current is switched on or switched off the rising or falling magnetic field also opposes the flow of current. This means that if an alternating supply is connected to the coil the opposition to the flow is greater than that due to the resistance alone.
The amount of opposition to a.c. depends upon the wire used, the number of turns, type of material inside the coil etc., and the effect is known as the inductance of the coil. Inductance is measured in henrys, and a small inductor may have a value of, say, 10mH.
There is also some capacitance associated with the coil, and this too affects the way it behaves with a.c. So the whole effect due to the resistance of the wire, the inductive effect and capacitive effect is summed up by referring to the impedance of the coil.
Impedance is the total opposition to a.c. and will depend upon the a.c. frequency. You will probably know that one of the important loudspeaker measurements is its impedance. If your amplifier has an output impedance of 8 ohm, then you need a speaker of 8ohm impedance if you wish to extract the maximum power.
Inductors are often used to reduce voltage spikes in a circuit – in fact you often see ferrous material wrapped around mains leads or other leads associated with computers, video recorders etc. Inductors are also used in radio tuning, and combined with capacitors can form a “tuned circuit” i.e. one which resonates with a particular frequency – to tune in your favorite radio station for instance.

Wednesday, May 02, 2012

Electro Magnetic Spectrum

VLSI Design Animation

Please CLICK HERE to watch a fantastic animation of the Complete VLSI Design Process.

All the steps from Wafer preparation to Packaging is explained here.


Tuesday, May 01, 2012

Communication- An Electronic Perspective

It is any transmission, emission, or reception of signs, signals,
writings, images and sounds or intelligence of any nature by
wire, radio, optical or other electromagnetic system

Communication model

A communication model comprises of following subsystems:
• Source – Generates the data to be transmitted
• Transmitter – Converts the data into transmittable signals
• Transmission system – Carries the data.
• Receiver – Converts received signals into data.
• Destination – Takes incoming data.