CT flashcards

Electronic Circuits 


Inductors 


Inductors are simply a coil or wire. Used in storing energy to form a magnetic field of energy. 


Inductors in AC Circuits


Inductors are extensively used in alternating current (AC) applications such as radio, TV and communications equipment 


Principles as transformers 


The purpose of a transformer is to change an electric system quantity (e.g., voltage or current) from one level to another.

A transformer is made up of two or more conductors wound around a single magnetic core, usually iron.


How do Transformers work? 


In a transformer there are two or more coils linked together by a common core conducting the magnetic flux. Flux from one coil (the primary winding) passes through the other coil (the

secondary winding), inducing a voltage in the secondary winding. Mutual induction links the two windings.



Turns ratio 


The amount a quantity changes is determined by the turns ratio, the magnetic flux links the turns of the primary and secondary windings.

This induces a voltage in each winding. Since the same flux cuts both windings, the same

voltage is induced in each turn of both windings.


The total voltage in each winding is proportional to the number of turns in that winding: 


V1 ÷ V2 = N1 ÷ N2


•V1 & V2 are voltage in primary and secondary windings

•N1 & N2 are number of turns in primary and secondary windings




Types of rectifier circuits 



Electric current 


Electric Current is the motion or flow of free electrons in a conducting material under the influence of potential difference. The material that contains free electrons is called conductors and they are used for conducting an electric current.


AC and DC


You should know: 


What is rectifier? 


A Rectifier is an electrical device that is made of one or more than one diodes that converts the alternating current (AC) into direct current (DC).


What is rectification?


Rectification is the process of conversion of the alternating current (which periodically changes direction) into direct current (flow in a single direction).


Types of rectifier: 


  1. UNCONTROLLED RECTIFIER: The type of rectifier whose output voltage cannot be controlled is called an uncontrolled rectifier.

  2. CONTROLLED RECTIFIER: A type of rectifier whose output voltage can be varied or changed is called controlled rectifier


Half wave rectifier: A type of rectifier that converts only the half cycle of the alternating current (AC) into direct current (DC) is known as halfwave rectifier.


 Positive and negative half wave rectifier


A positive half wave rectifier converts only the positive half cycle and blocks the negative half cycle.

A negative half wave rectifier converts only the negative half cycle of the AC into DC.


IMPORTANT NOTES:

In all types of rectifiers, a half-wave rectifier is the simplest of them all as it is composed of only a single diode.

A diode allows the current flow in only one direction known as forward bias. A load resistor RL is connected in series with the diode.


Full wave rectifier 

A full wave rectifier converts both positive and negative half cycles of the AC (alternating current) into DC (direct current). It provides double output voltage compared to the halfwave rectifier.


Bridge rectifier

A bridge rectifier uses four diodes to convert both half cycle of the input AC into DC output.



Advantages of a Bridge Rectifier:

1. Low ripples in the output DC signal

2. High rectifier efficiency

3. Low power loss

Disadvantages of Bridge Rectifier:

4. Bridge rectifier is more complex than a half-wave rectifier

5. More power loss compared to center-tapped full wave rectifier


CENTER-TAP RECTIFIER

This type of full-wave rectifier uses a center-tap transformer & two diodes



APPLICATIONS OF RECTIFIERS

Basically, almost all electronic circuits operated on DC voltages. The main purpose of using rectifier is for rectification which means converting AC voltages to DC Voltages. It means, rectifiers are used in almost all power rectification and electronics appliances.


Capacitor

A Capacitor is a device that stores electrical energy in an Electrostatic field. The energy is stored in such a way as to oppose any change in voltage.

A simple capacitor consists of two metal plates separated by an insulating material called a dielectric.


Capacitance is measured in units called FARADS. A one-farad capacitor stores one coulomb (a unit of charge (Q) equal to 6.28 x 10^18 electrons) of charge. (Faraday)


The action of a filter


WHAT IS A FILTER?

It is sometimes desirable to have circuits capable of selectively filtering one frequency or range of frequencies out of a mix of different frequencies in a circuit. A circuit designed to perform this frequency selection is called a filter circuit, or simply a filter.


A common need for filter circuits is in high-performance stereo systems, where certain ranges of audio frequencies need to be amplified or suppressed for best sound quality and power efficiency.


  • A filter is an AC circuit that separates some frequencies from others within mixed-frequency signals.

  • Audio equalizers and crossover networks are two well-known applications of filter circuits.

  • A Bode plot is a graph plotting waveform amplitude or phase on one axis and frequency on the other.


Why Do We Need Filters?

The ripple in the signal denotes the presence of some AC component.


This ac component has to be completely removed in order to get pure de output. So, we need a circuit that smoothens the rectified output into a pure DC signal.


A filter circuit is one which removes the ac component present in the rectified output and allows the dc component to reach the load.


SERIES INDUCTOR

A filter called Series Inductor Filter can be constructed by connecting the inductor in series, between the rectifier and the load.


SHUNT CAPACITOR

A filter called Shunt Capacitor Filter can be constructed using a capacitor, connected in shunt.


L-C FILTER

A filter circuit constructed using both inductor and capacitor to obtain a better output where the efficiencies of both inductor and capacitor can be used


PI-FILTER

Two capacitors and one inductor are connected in the form of I shaped network. A capacitor in parallel, then an inductor in series, followed by another capacitor in parallel makes this circuit.


WORKING OF A PI FILTER

• Capacitor C1 - This filter capacitor offers high reactance to de and low reactance to ac signal. After grounding the ac components present in the signal, the signal passes to the inductor for further filtration. 

•Inductor L - This inductor offers low reactance to dc components, while blocking the ac components if any got managed to pass, through the capacitor C1..

•Capacitor C2 - Now the signal is further smoothed using this capacitor so that it allows any ac component present in the signal, which the inductor has failed to block.


Voltage regulator 


Voltage regulator

A voltage regulator is a component of the power supply unit that ensures a steady constant voltage supply through all operational conditions.


A voltage regulator usually takes in higher input voltage and emits a lower, more stable output voltage.

Their secondary use is also to protect the circuit against voltage spikes that can potentially damage/fry them.


Linear regulators 

Their internal circuitry uses differential amplifiers to control output voltage against a reference voltage.


Linear regulators are widely used in sensitive audio equipment, analog sensors, and low-noise applications where stability and minimal ripple are more critical than efficiency. 


Switching regulators 


Because they alternate between fully on and fully off states, they reduce wasted energy and can achieve high efficiencies, often exceeding 90%, making them ideal for battery-operated devices, high-current applications, and situations where thermal management is crucial


Applications of voltage regulators

  1. Stable Operation or sensors and Microcontrollers

  2. Power Supply to Multiple Subsystems

  3. Protection Against Overvoltage and Undervoltage

  4. Improved Battery Efficiency

  5. Smooth and Reliable Actuator Control

  6. Prevention of Timing and Signal Errors in Digital Components

  7. Increased Safety in Critical Systems

  8. Efficient Power Management

  9. Compensation for Environmental Factors


Transistors 


The transistor was first developed in 1949 at Bell Telephone Laboratories, the name being derived from "transfer resistor"


The transistor is best described as a current amplifier - it uses a small amount of current to control a large amount of current.

There are many different families of transistors but we will only discuss the type called the NPN Bipolar Junction Transistor or BJT and made of the semiconductor silicon.


It has three connection points, called the emitter, base, and collector.

  • The emitter is the region on one side that emits electrons or holes (depending on the type of transistor) into the base.

  • The base is the middle region, which is thin and lightly doped.

  • The collector is the region on the other side that collects these charge carriers from the base.

NPN transistor is a type of bipolar junction transistor (BJT) that is composed of two layers of N-type semiconductor material, with a layer of P-type material sandwiched in between.

The term NPN is derived from the sequence of these semiconductor layers 


Applications of NPN Transistors

• Amplification circuits - amplifies a weak input signal to produce a larger output signal

•Digital logic circuits - transistor acts as a switch that turns on or off based on the input signals, thereby performing the logic operation

•Power electronics - transistor controls the flow of large currents and operates at high voltages


Applications of NPN Transistors

•Oscillators - the transistor, in combination with other components like resistors, capacitors, and diodes, forms a feedback loop that oscillates at a specific frequency

• NPN sensors - used in applications where a sinking output is desired, including PLCs, proximity sensors, capacitive sensors, and photoelectric sensors


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