What Makes A Dad?

What Makes A Dad?

God took the strength of the mountain,
Majesty of a tree,
Warmth of the sun,
The calmness of the sea.
He took the generous soul of nature,
Comforting arm of the night,
Wisdom of the ages,
And the power of the eagle's flight.
He endorsed joy of the morning spring,
Faith of the mustard seed,
Patience of the eternity,
And the depth of a family need.
Then God combined these qualities,
When there was nothing more to add,
He knew his masterpiece was ready,
And so, he named it Dad.

~Jay Mehta

The Remembrance

The Remembrance.

The days have come and passed,

Time has blown way too fast,

I was mesmerized,

And before I could wake up,

I found myself reliving my past.

It seemed I had just entered it,

But it had been long since I was living it.

I remembered each folly I made,

 The mistakes that were corrected,

I inculcated the lessons I learned,

I remembered the hand that had been burned.

I was missing all the teachers caring,

I missed the friends who were tricksters.

That was the most carefree time,

That came back with a wonderful chime.

I wished to live that life again,

But that would just be so lame.

Hence, I made a new wish,

And asked for more such memories that I could cherish.

~ Jay Mehta

~Jay Mehta

The Day I Woke Up !

This poem was written by me when I was in ninth grade. It might not be that impressive but me being in ninth grade writing this meant a lot to me and my parents. It was appreciated by my class teacher who even was my English teacher back then. I would like to acknowledge my mentor Mrs. Nandita Ganguly who also appreciated my work and kept me motivated to keep on writing stuff that interested me.

THE DAY I WOKE UP

The days were cool,

And nights were easy,

I just thought of some tools,

And my life became busy.

With a sigh of laziness,

I found the world very hard,

Because I was crazy, for the card.

This made all the difference,

I challenged my appearance,

Until the day had come,

When I woke up.

To jump to reach newer heights,

I had already taken the eagle’s flight.

Things looked colorful,

And surroundings turned bright.

I got my destiny, I reserved all my rights.

My life became honorable,

When a book got my label.

By Jay Mehta.

~Jay Mehta

The Farewell Song !

This was the song sung by my batch for our seniors who were mostly likely to leave our school and join some other college for their higher education.

I am not the lyricist of the song written below, and I am unaware of the author's name.

Farewell: 

The days go so fast, I know they won't last,

I am gonna miss this school so much,

The magic of school life, the joy, and the needful strife,

And now we are walking away.

These are those moments yeah...

Which keeps me, surviving up to death.

These are those moments yeah...

The Annual Day furry, Parents Day in a hurry,

The fun that we had on Sports Day,

I realize the school was the best thing forever,

And how we are walking away.

These are those moments yeah...

Which makes me feel, live them again.

These are those moments yeah...

But this is just a part of our lives,

We got to lose something sometime,

But now we shall work hard,

And make our school glow with pride.

          ~(UNKOWN)

~Jay Mehta

Studying CRO-CathodeRayOscilloscope

Q. What is Cathode Ray Oscilloscope? 

A. Cathode-ray oscilloscope, an electronic-display device containing a cathode–ray tube (CRT) that generates an electron beam that is used to produce visible patterns, or graphs, on a phosphorescent screen.

The graphs plot the relationships between two or more variables.With Horizontal axis normally being a function of time and Vertical axis normally being a function of the voltage generated by input or output signal. We take voltage as the vertical axis because we can almost convert any physical quantity to it’s corresponding electrical voltage. This makes the OSCILLOSCOPE a versatile tool for measuring various quantities and seeing the respective graph formations.

THE GERMAN PHYSICIST FERDINAND BRAUN DEVELOPED THE FIRST CATHODE-RAY-OSCILLOSCOPE IN 1897.

The central component of the device is the CRT(Cathode-Ray-Tube). It is the heart of the CRO that gives you the graph on the phosphorescent screen.

Cathode-Ray-Tube consist of the evacuated glass container with the phosphorescent coating at one end and an electron gun at the other end with a focusing, accelerating and deflecting system in between them.

General INFO of a general purpose CRO:-

1. Screen Size– 10 cm X 8 cm. graticule.(most common).
2. Phosphor– The screen is coated on the inside with a fluorescent material called ‘Phosphor’. It decides the colour and the persistence of the trace.
   • Persistence-is the length of time the trace remains on the screen after the signal has ended. It is expressed as SHORT,MEDIUM and LONG.
   • Short Persistence- is used for extremely high-speed phenomena.
   • Medium Persistence- are used for general purpose applications.
   • Long Persistence- are used for transients, since they keep the fast transient on the screen for observation after the transient as disappeared.
3. Operating_Voltage– CRT requires a heater voltage of 3V-6V AC/DC at 600mA.
4. Deflection_Voltage- AC or DC both voltages deflect the beam. The distance through which the point on the screen moves is propotional to the DC voltage or the AC peak voltage.
5. Vertical Amplifier- determines to characteristics, SENSITIVITY and FREQUENCY BANDWIDTH response.  The attenuator used at the input stage of the verticle amplifier gives the V/div control on the front panel.
6. Delay Line- is used to delay the signal in the vertical section. The signal in the horizontal has to pass through the TRIGGER PICK OFF circuit, TIME BASE generator and the HORIZONTAL AMPLIFIER before reaching to the horizontal deflection system. Thus a delay line circuit is use to delay the vertical signal so that we get a perfect trace on the screen.
   • The time taken for the signal to pass through the Horizontal Section is 80ns and the Delay Line used is 200ns so that the Horizontal Sweep signals start in time.
7. Time_Based_Generator-is used to generate the sawtooth voltage required to deflect the beam in the horizontal section. The circuit used is CONTINUOUS SIGNAL GENERATOR. As this circuit can not withstand (follow) the variations of fast varying signals the circuit is modified and is now called TRIGGERED SWEEP GENERATOR. The timing of the time base generator gives the Time/div control on the front panel of CRO.
8. Horizontal_Amplifier- is used to amplify the sawtooth voltage before it is applied to the horizontal deflection system. This block consist of PUSH-PULL AMPLIFIER.
9. Trigger_Circuit- is used to convert the incoming signal into triggered pulse, so that the input signal and the sweep frequency can be synchronised. It is activated by variety of signals which are then converted to trigger pulse of the uniform amplitude. If the trigger is to low the circuit will not operate and if it is to high the UNI-JUNCTION TRANSISTOR (UJT) will conduct for too long and the part of the leading edge of the trace signal would be lost. It is operated by a three position switch INTERNAL, EXTERNAL and LINE on the front panel.
10. Power_Supply- CRO uses two power supplies, A NEGATIVE HIGH VOLTAGE and A POSITIVE LOW VOLTAGE. 

• Advantages of the high negative supply:
  • less insulation is required between the positioning controls and the chassis.
  • the accelerating anodes and the deflection plates are close to the ground potential. this ground potential protects the user from the high voltage shocks when making connections to the plates.
  • the deflection voltage are measured with respect to the ground potential hence high voltage blocking or coupling capacitors are not needed.

FRONT PANEL CONTROLS:-

1. Power:-Puts the instrument to main supply or cut it off with a LED indication.
2. Intensity:-Controls the brightness of the trace.
3. Focus:-Controls the sharpness of the trace.
4. Time Base:-18 step switch (normally) which enables the selection of 18 calibrated sweeps ranging from 0.5 microseconds/division to 0.2 s/div.
5. Time Base Variable:-Extends or holds the sweep speed of the wave in clockwise direction.
6. Hold :-makes the signal steady.
7. X Position:- Moves the trace left or right along the horizontal axis.
8. Y Position:- Moves the trace up and down along the vertical axis.
9. Level:- Controls variable speed and multiple waveform and selects the trigger point.
10. Auto/Normal:- In auto mode CRO displays a wave in absence of any input signal.
11. Ext/Int:-
    • EXT:-displays trigger derived from any external source.
    • INT:- displays trigger derived from CH1,Ch2, and LINE.
12. Line:-triggers the trace from power line frequency.
13. +/-:-Selects trigger point on either positive or negative slope of the displayed waveform.
14. AC/DC:-Selects trigger signal compiling.
15. HF rej:- Introduces the low pass filter in the trigger compiling.
16. 0.2 V, 1 kHz:-200mV(peak to peak), 1kHz square wave calibration.
17. GND:-selects input grounding.
18. EXT.TRG:- input BNC for external trigger signal. Checks if CRO is working properly or not.

~Jay Mehta

Bipolar Junction Transistors:

• Emitter layer is heavily doped region.
• Collector layer is mediocre doped region.
• Base layer is lightly doped region.

The lower doping level decreases the conductivity (increasing the resistance) of the material by limiting the “free carriers”.

The term “BIPOLAR” reflects the fact that holes and electrons participate in the injection process into the oppositely polarized material.

If only one carrier is employed (electron or hole) than it is called a “UNIPOLAR”device.

Transistor Operation For A PNP Transistor:

1. If we disconnect the base to collector bias we can compare the present state of PNP transistor to the forward bias diode.
   1. The depletion region, in this case, would have been reduced in width due to the applied bias;
   2. Resulting in heavy flow of majority charge carriers from p to n-type material in the transistor;
2. If we disconnect the emitter to base bias we can compare the present state of PNP transistor to the reversed bias diode.
   1. The depletion region in this case would have increased its width due to the applied reverse bias;
   2. Resulting in very less flow of minority charge carriers from n to p-type of the transistor.
3. Hence, we see that in proper DC biasing of the PNP transistor, one of the PN junction is forward biased and the other has to be reversed biased. 
4. When both the bias are applied for normal functioning of the PNP Transistor:
   1. In this case, emitter-base bias is forward biased and collector base bias is reversed so, the depletion region formed between emitter-base junctions would be of smaller width whereas, collector-base junction would have a large depletion region.
   2. As a result majority carriers would flow from the emitter (p region) to base (n region) and these carriers will flow into the collector (p region) directly as they experience large resistance at the base terminal due to its low doping level. This results in a very low base current (Ib) which is in the range of microamperes whereas, emitter and collector currents (Ie and Ic respectively) are in the range of milliamperes.
      Ie = Ic + Ib
   3. Collector currents comprises of two components:-
      1. Collector current due to majority charge carriers. (IC_majority);- this is also known as the leakage current. 
      2. Collector current due to minority charge carriers with emitter terminal open. (Ico_minority);- this is measured in nanoamperes and can be compared to reverse saturation current of a diode (Is).

 Ic = IC_majority   +  Ico_minority

Configurations:

1. Common Base Configurations: 
   1. Ic approximately equals to I­e   in active region.
   2. In cut-off region Ic = 0A; (cut off region is the region that develops as a result of the condition when both junctions are reversed biased).
   3. In saturation region (when both junctions are forward biased), Ve = 0.7V(always for all cases.) 
   4. Alpha(dc) = Ic / Ie ; 
   5. Value of alpha is always approaching 1 alpha = 0.996 in real life conditions (0.9). 
2. Common Emitter Configurations:
   

~Jay Mehta

LOAD LINE ANALYSIS AND VOLTAGE MULTIPLIER

LOAD LINE ANALYSIS

The straight line in the above graph is called the LOAD LINE because the intersection of the vertical axis is defined by the applied load R. the analysis to follow is therefore called LOAD LINE ANALYSIS.

The load line plots all possible combinations of diode current (Id) and voltage (Vd) for a given circuit. The maximum Id equals Vdd/R, and the maximum Vd equals Vdd.

The point where the load line and the characteristic curve intersect is the Q-point, which identifies Id and Vd for a particular diode in a given circuit.Q-point (quiescent point) decides the solution for the network and defines the current and voltage levels for the network.

Since the current going through the three elements in series must be the same, and the voltage at the terminals of the diode must be the same, the operating point of the circuit will be at the intersection of the curve with the load line.

The intersection of the two curves can be determined by applying KVL equation to the circuit (given in the fig. above),we get:

Vdd = Vd + Id*R;

Substituting Vd and Id equal to zero(one by one) we will get two points, one on x-axis and the other on y-axis respectively. When we join this two points we will get a straight line intersecting the characteristic curve of the device. This is how we get the load line.

Changing the value of R, the point of intersection on y-axis will also change (Id=Vdd/R).Thus changing the slope of the curve and point of intersection with the characteristic curve, hence changing the operating point of the device.

VOLTAGE MULTIPLIER 

A voltage multiplier is an electrical circuit that converts AC electrical power from a lower voltage to a higher DC voltage, typically by means of a network of capacitors and diodes.

Voltage multipliers can be used to generate bias voltages ranging from a few volts for electronic appliances to millions of volts for purposes such as high-energy physics experiments and lightning safety testing.

VOLTAGE DOUBLER 

HALF WAVE VOLTAGE DOUBLER :

The network shown above is the circuit diagram for half wave voltage doubler circuit.

During the positive half cycle of the input signal is given to the circuit the diode D1 conducts(and diode D2 is cut off), this leads to the charging of the capacitor C1 to Vi volts with the positive charge getting created on the plates close to the input signal and negative charge being formed on the plates further from the input.

During the negative half cycle of the input signal diode, D1 is cut off and diode D2 is conducting charging the capacitor C2.

Since diode D2 acts as a short during the negative half cycle(and D1 acts as open), we can sum the two voltages around the outside loop:

-Vi – Vc1 + Vc2 = 0

-Vi – Vi + Vc2 = 0 (as the capacitor C1 starts acting as a battery, as it could not discharge)

Therefore, capacitor C2 charges up to 2Vi.

On the next positive half cycle, diode D2 is non-conducting and capacitor C2 will discharge through the load. If no load is connected across the capacitor C2, both the capacitors stay charged — C1 to Vi and C2 to 2Vi. 

If, as would be expected, there is a load connected to the output, so the voltage across C2 will drop during the positive half cycle(at input) and will recharge up to 2Vi during the negative half cycle.

The output waveform across C2 is that of the capacitor filtered half wave signal. The peak inverse voltage across each diode is 2Vi.

FULL WAVE VOLTAGE DOUBLER :

The above circuit shows a basic symmetrical voltage multiplier circuit made up from two half-wave rectifier circuits. By adding a second diode and capacitor to the output of a standard half-wave rectifier, we can increase its output voltage by a set amount. This type of voltage multiplier configuration is known as a Full Wave Series Multiplier because one of the diodes is conducting in each half cycle, the same as for a full wave rectifier circuit.

When the sinusoidal input voltage is positive, capacitor C1 charges up through diodeD1 and when the sinusoidal voltage is negative, capacitor C2 charges up through the diode, D2. The output voltage 2VP is taken across the two series connected capacitors.

~Jay Mehta