What is a resistor?

Answer: A resistor is an electrical component that limits or regulates the flow of electrical current in an electronic circuit. Resistors can also be used to provide a specific voltage for an active device such as a transistor.

2. If you connect two pcs 10 ohm resistors in series circuit, what will be the total resistance?

Answer: R (total in series) =10+10=20 ohm.

3. Just change connection series to parallel at circuit of above question, what will be the total resistance?

Answer: R (total in parallel) = (10x10)/(10+10)=5 ohm.

Several types of diodes are available for use in electronics design. Some of the different types are:

Light Emitting Diode (LED):

It is one of the most popular type of diodes and when this diode permits the transfer of electric current between the electrodes, light is produced. In most of the diodes, the light (infrared) cannot be seen as they are at frequencies that do not permit visibility. When the diode is switched on or forward biased, the electrons recombine with the holes and release energy in the form of light (electroluminescence). The color of light depends on the energy gap of the semiconductor.

Avalanche Diode:

This type of diode operates in the reverse bias, and used avalanche effect for its operation. The avalanche breakdown takes place across the entire PN junction, when the voltage drop is constant and is independent of current. Generally, the avalanche diode is used for photo-detection, wherein high levels of sensitivity can be obtained by the avalanche process.

Laser Diode:

This type of diode is different from the LED type, as it produces coherent light. These diodes find their application in DVD and CD drives, laser pointers, etc. Laser diodes are more expensive than LEDs. However, they are cheaper than other forms of laser generators. Moreover, these laser diodes have limited life.

Schottky Diodes:

These diodes feature lower forward voltage drop as compared to the ordinary silicon PN junction diodes. The voltage drop may be somewhere between 0.15 and 0.4 volts at low currents, as compared to the 0.6 volts for a silicon diode. In order to achieve this performance, these diodes are constructed differently from normal diodes, with metal to semiconductor contact. Schottky diodes are used in RF applications, rectifier applications and clamping diodes.

Zener diode:

This type of diode provides a stable reference voltage, thus is a very useful type and is used in vast quantities. The diode runs in reverse bias, and breaks down on the arrival of a certain voltage. A stable voltage is produced, if the current through the resistor is limited. In power supplies, these diodes are widely used to provide a reference voltage.

Photodiode:

Photodiodes are used to detect light and feature wide, transparent junctions. Generally, these diodes operate in reverse bias, wherein even small amounts of current flow, resulting from the light, can be detected with ease. Photodiodes can also be used to generate electricity, used as solar cells and even in photometry.

Varicap Diode or Varactor Diode:

This type of diode feature a reverse bias placed upon it, which varies the width of the depletion layer as per the voltage placed across the diode. This diode acts as a capacitor and capacitor plates are formed by the extent of conduction regions and the depletion region as the insulating dielectric. By altering the bias on the diode, the width of the depletion region changes, thereby varying the capacitance.

Rectifier Diode:

These diodes are used to rectify alternating power inputs in power supplies. They can rectify current levels that range from an amp upwards. If low voltage drops are required, then Schottky diodes can be used, however, generally these diodes are PN junction diodes.

Small signal or Small current diode -

These diodes assumes that the operating point is not affected because the signal is small

Large signal diodes

The operating point in these diodes get affected as the signal is large.

Transient voltage supression diodes

This diode is used to protect the electronics that are sensitive against voltage spikes.

Gold doped diodes

These diodes use gold as the dopant and can operate at signal frequencies even if the forward voltage drop increases.

Super barrier diodes

These are also called as the rectifier diodes. This diodes have the property of low reverse leakage current as that of normal p-n junction diode and low forward voltage drop as that of Schottky diode with surge handling ability.

Point contact diodes

The construction of this diode is simpler and are used in analog applications and as a detector in radio receivers. This diode is built of n – type semiconductor and few conducting metals placed to be in contact with the semiconductor. Some metals move from towards the semiconductor to form small region of p- tpye semiconductor near the contact.

Peltier diodes

This diode is used as heat engine and sensor for thermoelectric cooling.

Gunn diode -

This diode is made of materials like GaAs or InP that exhibit a negative differential resistance region.

Crystal diode -

These are a type of point contact diodes which are also called as Cat’s whisker diode. This didoe comprises of a thin sharpened metal wire which is pressed against the semiconducting crystal. The metal wire is the anode and the semconducting crystal is the cathode. These diodes are obsolete.

Avalanche diode -

This diode conducts in reverse bias condition where the reverse bias volage applied across the p-n junction creates a wave of ionization leading to the flow of large current. These didoes are designed to breakdown at specific reverse voltage in order to avoid any damage.

Silicon controlled rectifier -

As the name implies this diode can be controlled or triggered to the ON condition due to the application of small voltage. They belong to the family of Tyristors and is used in various fields of DC motor control, generator field regulation, lighting system control and variable frequency drive . This is three terminal device with anode, cathode and third controled lead or gate.

Vacuum diodes -

This diode is two electrode vacuum tube which can tolerate high inverse voltages.

Diodes are used widely in the electronics industry, right from electronics design to production, to repair. Besides the above mentioned types of diodes, the other diodes are PIN diode, point contact diode, signal diode, step recovery diode, tunnel diode and gold doped diodes. The type of diode to transfer electric current depends on the type and amount of transmission, as well as on specific

Rectifier:

A rectifier is an electrical device composed of one or more diodes that converts Alternating Current (AC) to Direct Current (DC). A diode is like a one-way valve or semiconductor device that allows an electrical current to flow in only one direction. This process is called rectification. Rectifiers are used in various devices, such as, DC power supplies, Radio signals or detectors, a source of power instead of generating current, High-voltage direct current power transmission systems and several household appliances use power rectifiers to create power, like notebooks or laptops, mobile phone, video game systems and televisions etc

1. What is Rectifier?

Answer: A rectifier is an electrical device composed of one or more diodes that converts alternating current (AC) to direct current (DC).

2. What is Diode?

Answer: A diode is like a one-way valve or semiconductor device that allows an electrical current to flow in only one direction.

3. Can you mention some household application of rectifier?

Answer: Notebooks or laptops, mobile phone, video game systems and televisions etc.

Sensor :

• A sensor is a device that detects and responds to some type of input from the physical environment. The specific input could be light, heat, motion, moisture, ...

Different type of sensor

• Proximity Sensor : A proximity sensor is a sensor able to detect the presence of nearby objects without any physical contact. Proximity Sensor - this usually turns the screen off when you hold it up to your head while on a phone call so you don't accidentally "push" any Button. Save battery power
• 1. What is Proximity Sensor?

Answer: A Proximity Sensor is a sensor able to detect the presence of nearby objects without any physical contact.

2. How does it work?

Answer: A proximity sensor often emits an electromagnetic field or a beam of electromagnetic radiation (infrared, for instance), and looks for changes in the field or return signal.

3. What type of proximity sensor is used now-a-days in smart phone?

Answer: IR (infrared)-based proximity sensor.

4. Why proximity sensor is used in smart phone?

Answer: Now-a-days, smart mobile phones use IR (infrared)-based proximity sensors to detect the presence of a human ear.

5. What is the benefit of sensing of proximity sensor?

Answer: Reduce display power consumption by turning off the LCD backlight and to disable the touch screen to avoid inadvertent touches by the cheek.

Accelerometer sensor :

An accelerometer is a sensor that measures the acceleration forces. On most modern mobile devices there is a 3-way axis device that determines the phone’s physical position. By measuring the static acceleration due to gravity you can find the angle at which device is tilted and by measuring the dynamic acceleration due to movement you can analyze the direction in which the device is moving.

This sensor is available for both the Android and iPhone runtimes .Use for Screen rotation

What is the use of accelerometer sensor in mobile phones?

Accelerometers in mobile phones are used to detect the orientation of the phone. The gyroscope, or gyro for short, adds an additional dimension to the information supplied by the accelerometer by tracking rotation or twist.

Digital Sensor : For Digital Compus, location.

Gyro sensor : 3D games, 3D maps.

Grip Sensor : For motion control

Hall Sensor:

A Hall Sensor or Hall Effect Sensor is a transducer (a device that converts variations in a physical quantity, such as pressure or brightness, into an electrical signal, or vice versa) that varies its output voltage in response to a magnetic field. This sensors are used for proximity switching, positioning, speed detection, and current sensing applications. The main function of this proximity sensor is to detect how close your smartphone's screen is to your body.

1. What is Hall Sensor?

Answer: A Hall Sensor or Hall Effect Sensor is a transducer that varies its output voltage in response to a magnetic field.

2. What is transducer?

Answer: Transducer is a device that converts variations in a physical quantity, such as pressure or brightness, into an electrical signal, or vice versa.

3. What is the function of this sensor at smart phone?

Answer: This sensors are used for proximity switching, positioning, speed detection, and current sensing applications. The main function of this proximity sensor is to detect how close your smartphone's screen is to your body

Geotagging:

Now-a-days almost everyone has a smartphone and with the rise of mobile technology comes the opportunity to "geotag" specific content you post on social networks. Geotagging (also written as Geo Tagging) is the process of adding geographical identification metadata to various media such as a geotagged photograph or video, websites, SMS messages, QR Codes or RSS feeds and is a form of geospatial metadata. This data usually consists of latitude and longitude coordinates, though they can also include altitude, bearing, distance, accuracy data, and place names, and perhaps a time stamp. Geotagging a location to your posts gives your friends and followers a deeper glimpse into where you are and what you're doing.

1. What is Geotagging?

Answer: Geotagging (also written as GeoTagging) is the process of adding geographical identification metadata to various media such as a geotagged photograph or video, websites, SMS messages, QR Codes or RSS feeds and is a form of geospatial metadata.

2. What type of information is usually added at geospatial metadata?

Answer: This data usually consists of latitude and longitude coordinates, though they can also include altitude, bearing, distance, accuracy data, and place names, and perhaps a time stamp.

3. What is the benefit of Geotagging?

Answer: Geotagging a location to your posts gives your friends and followers a deeper glimpse into where you are and what you're doing.

By substituting di/dt in the above equation with v/L gives:

Inductors in Parallel Example No1

Three inductors of 60mH, 120mH and 75mH respectively, are connected together in a parallel combination with no mutual inductance between them. Calculate the total inductance of the parallel combination in millihenries.

Inductor in Series Circuit

The current, ( I ) that flows through the first inductor, L₁ has no other way to go but pass through the second inductor and the third and so on. Then, series inductors have a Common Current flowing through them, for example:

I_L1 = I_L2 = I_L3 = I_AB …etc.

In the example above, the inductors L₁, L₂ and L₃ are all connected together in series between points A and B. The sum of the individual voltage drops across each inductor can be found using Kirchoff’s Voltage Law (KVL) where, V_T = V₁ + V₂ + V₃ and we know from the previous tutorials on inductance that the self-induced emf across an inductor is given as: V = L di/dt.

So by taking the values of the individual voltage drops across each inductor in our example above, the total inductance for the series combination is given as:

By dividing through the above equation by di/dt we can reduce it to give a final expression for calculating the total inductance of a circuit when connecting inductors together in series and this is given as:

Inductors in Series Equation

L_total = L₁ + L₂ + L₃ + ….. + L_n etc.

Then the total inductance of the series chain can be found by simply adding together the individual inductances of the inductors in series just like adding together resistors in series. However, the above equation only holds true when there is “NO” mutual inductance or magnetic coupling between two or more of the inductors, (they are magnetically isolated from each other).

One important point to remember about inductors in series circuits, the total inductance ( L_T ) of any two or more inductors connected together in series will always be GREATER than the value of the largest inductor in the series chain.

Inductors in Series Example No1

Three inductors of 10mH, 40mH and 50mH are connected together in a series combination with no mutual inductance between them. Calculate the total inductance of the series combination.

RF & IF Amplifiers and Filters

IF:

The intermediate frequency is created by mixing the carrier signal with a local oscillator signal in a process called heterodyning, resulting in a signal at the difference or beat frequency.

RF:

A radio frequency amplifier, or RF amplifier, is a tuned amplifier that amplifies high-frequency signals used in radio communications. The frequency at which maximum gain occurs in an RF amplifier is made variable by changing the inductance or capacitance of the tuned circuit.

EMI and ESD Filters

EMI: An EMI filter, or electromagnetic interference filter, is an electronic passive device which is used in order to suppress conducted interference that is present on a signal or power line.

ESD Filters

1. EMI/ESD Filters for Cellular Phones. Cellular phones, as with all handheld and wireless devices are susceptible to the damaging effects of Electrostatic Discharge (ESD) transients. As much as 40 kilovolts of ESD can be generated by the human body or through air discharge.

1. What is inductor?

Answer: An inductor, also called a coil or reactor, is a passive two-terminal electrical component that stores electrical energy in a magnetic field when electric current is flowing through it.

2. Three inductors of 10mH, 40mH and 50mH are connected together in a series combination with no mutual inductance between them. Calculate the total inductance of the series combination.

Answer :

3. Mention some real life example of inductor?

Answer: Applications of inductor in our daily life are transformers, power supplies, TVs, radios, radars etc.

What is the meaning of MAH?

A: The mAh stands for milli-Ampere-hours and indicates how much electric charge the battery can provide. For example, if you discharge your battery through a circuit that requires 1 milli-Ampere of current it will last 800 hours before the battery runs down.

What do you mean by standby time?

Standby time refers to the amount of time a phone can remain powered on while not being used. And I mean not being used in the sense of at all. That means no incoming or outgoing texts, messages, phone calls, emails or any thing else that alters the data on the phone.

IMEI:

The International Mobile Equipment Identity or IMEI is a number, usually unique, to identify 3GPP (i.e., GSM, UMTS and LTE) and iDEN mobile phones, as well as some satellite phones. It is usually found printed inside the battery compartment of the phone, but can also be displayed on-screen on most phones by entering *#06# on the dialpad, or alongside other system information in the settings menu on smartphone operating systems.

The IMEI number is used by a GSM network to identify valid devices and therefore can be used for stopping a stolen phone from accessing that network. For example, if a mobile phone is stolen, the owner can call their network provider and instruct them to "blacklist" the phone using its IMEI number. This renders the phone useless on that network and sometimes other networks too, whether or not the phone's SIM is changed.

1. What is IMEI?

Answer: The International Mobile Equipment Identity or IMEI is a number, usually unique, to identify 3GPP (i.e., GSM, UMTS and LTE) and iDEN mobile phones, as well as some satellite phones.

2. How can we find IMEI from HS?

Answer: IMEI is usually found printed inside the battery compartment of the phone, but can also be displayed on-screen on most phones by entering *#06# on the dialpad, or alongside other system information in the settings menu on smartphone operating systems.

3. How does IMEI reduce HS stolen incident?

Answer: If a mobile phone is stolen, the owner can call their network provider and instruct them to "blacklist" the phone using its IMEI number. This renders the phone useless on that network and sometimes other networks too, whether or not the phone's SIM is changed.