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Answers for E.C.E 4

Below are the answers for questions asked in E.C.E 4

  1. Speech amplifiers are mainly used as Class A amplifiers.
  2. In a low level AM system, amplifier following the modulated stage must be a Linear Device.
  3. Linearity
  4. If the modulation index is more than 100% then modulated carrier signal will periodically reduced to zero. This will not effect the working of transmitter but the receiver will produce a distorted output.
  5. Modulation is the process of converting one or more property of a high frequency Carrier wave according to the input signal. 
  6. -
  7. Class C
  8. -
  9. A linear amplifier
  10. 0 to 1
  11. 100 watts
  12. With the help of formula of capacitance of parallel plates i.e. 

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Learn Maxwell Equations

Maxwell equations are basically a relationship between electricity and magnetism. These are 4 basic equations represents Maxwell equations :-

Now let's talk about these equations one by one

Equation no. 1 

This law states that flow of electric field associated with a particular region is equal to the total charge present in that region divided by a constant( permittivity of free space ).

Equation 2 

It stats that magnetic field remains constant and for a given space it remains zero.

Equation 3

Also Known as Faraday's Law of induction.

Equation no.4

Also known as Ampere's Law as amended by Maxwell, and also known as

∇×H = J +

Symbols of Different Transistors

There are mainly 2 families of Transistor i.e. Bipolar and Uni-polar Transistors.
Bipolar Transistors have 2 kind of carriers both holes and electrons while Unipolar Transistors 
have only single carrier either Hole or electrons.

Below are the symbols for BJT, FET, MOSFET, Duel gate MOSFET, Inductive channel MOSFET and Single connection Transistor.

fig a - BJT
fig b - FET
fig c - MOSFET
fig d - Duel gate MOSFET
fig e - Inductive Channel MOSFET
fig f - Single connection Transistor


Network Theorems

Superposition Theorem

The response in any element of linear, bilateral network containing more than one source is the sum of the response produced by the sources each acting independently.
The superposition principle is only applicable to linear networks and systems.
The superposition theorem does not apply to the power as power is proportional to square of the current which is not a linear function.
  1. Select a single source. Short the other voltage sources and open the current source, if internal impedance's are not known. If known than replace them by their internal impedance.
  2. Find out the current through or the voltage across the required element, due to the source under consideration.
  3. Repeat the above step for all the sources.
  4. Add all the individual effect produced by individual sources to obtain the total current in or voltage across the element.

Thevenin's Theorem

Any combination of linear bilateral circuit elements and active sources, regardless of the connection and complexity, connected to a given load Zmay be replaced by a single two terminal network consisting of a
Single voltage source of VTH and a single impedance Zeq in the series with the voltage source, across the two terminals of the load ZL.
1.       Remove the branch impedance, through which current is required to calculate.
2.       Calculate the voltage across the open circuited terminals. This voltage is Thevinin’s equivalent voltage VTH .
3.       Calculate the equivalent impedance Zeq as viewed through the two terminals of the branch from which current is to be calculated by removing that branch impedance and replacing all the independent sources by their internal impedance.
4.       The required current through the branch is given by, I = VTH / ZL + Zeq .

Norton’s Theorem

Any combination of linear bilateral circuit elements and active services regardless of the connection or complexity, connected to a given load ZL can be replaced by a simple two terminal network consisting of a single current source of IN and a single impedance Zeq in parallel with it, across the two terminals of the load ZL .
1.       Short the branch through which the current is to be calculated.
2.       Find out the current through this short circuited branch. This current is nothing but the Norton’s current IN.
3.       Calculate the equivalent impedance Zeq as viewed through the two terminals of interest by removing the branch impedance and making all the independent sources inacticve.
4.       The current through the branch of interest is  I = IN * Zeq / ZEQ + ZL.