Electrical Resonance

Resonance

What's Resonance?

resonance is the state at which any element is naturally oscillate at the frequency they like to oscillate 

when connecting an initially charged capacitor with an inductor we notice that energy which stored at capacitor as an electric field transfer to inductor which store energy as magnetic field.

so what happen there?
capacitor charge indutor until it fully charged so capacitor at this moment fully discharged then inductor charge capacitor back until it fully charged and indutor fully discharged. this cycle continues forever if there's no losses in the wiring system but in fact this energy gradually die out because of losses.
this circuit act like a pendulum, in pendulum kinetic energy transfer into potential energy then potential transfer into kinetic and so on until it stops because of losses so LC circuit and pendulum oscillate at frequency they like
 so this state is called resonance.

Condition Of Electrical Resonance Occurrence:

Resonance in electrical system occur when supply drives circuit at resonance frequency.
at resonance frequency capacitor reactance is equal inductor reactance.

So resonance  frequency is:

Series Combination Of RLC Circuit In Resonance:

when applying voltage source with frequency equal to resonance frequency the combination of LC will act like a short circuit. 
as circuit element are connected in series so the current is the same passing through all element RLC so let us consider the current as reference.

at inductor: 
the voltage leads the reference current by 90 degree.
at capacitor:
the voltage lags the reference current by 90 degree.

so when adding capacitor voltage and inductor voltage at resonance we notice that they have the same magnitude and out of phase by 180 degree and the resultant voltage become zero so that LC acting like short circuit and the series resistor have all supply voltage.




Parallel Combination Of RLC Circuit In Resonance:

when connecting element in parallel the voltage is the same at the capacitor and inductor so let us take it as a reference.
 
at inducor: 
the current lags the reference voltage by 90 degree.
at capacitor:
the current leads the reference voltage by 90 degree.

so when adding capacitor current and indutor current together at resonance we notice that they have the same magnitude and out of phase by 180 degree so the resultant current become zero and combination of LC act like an open circuit and all current is passing through the resistor only.

Types of Diode

Types of diode

Diode is a one way valve, it mean that it allow current on one direction and block current in the other direction.

it has two terminal: anode and cathode 

and has two state: 

1-forward bias: connect positive rail of supply to anode and negative rail to cathode in that condition diode allow current but has voltage drop across it depend on material of diode.

2-Reverse bias: connect positive rail of supply to cathode and negative rail to anode in that condition diode block current and it act like open circuit with very small leakage current.

Diode generally made of silicon or germanium , these three material have a voltage drop 0.7 , 0.3 respectively.

let's discuss types of diode and application of every type.

Normal Diode:
It also called general purpose diode. it have meduim to high volltage drop, low current rating , low speed rectifier and inefficient for square wave more than 15kHZ.

Power Diode:

It also called rectifier diode . it has high current rating in ampere depend on the required application it usually came on large size 
these diode used in power supply or voltage doubler circuit.

Small Signal Diode:
When dealing with high frequency and small current in mA, so this kind of diode is convenient
it has small size and enveloped with glass to protect it from contamination.

it characterized by low power consumption in mw
and widely used in radio and television application.

Light Emitting Diode (LED):
These diode isn't only allow current in one direction but also emit light .

it has high forward voltage rating compared to normal diode, also rating forward voltage depend on the color.

for example:V_F of red LED is around 2.2V and blue is 3.3V

some of these LED are invisible such as infrared LED which are commonly used in remote control application.

Photo Diode:

This type of diode consume light energy and convert it into current

sensing light in reverse bias operation is the main function of these diode

in addition of sensing , large area of this photo diode can generate electricity in that case it used as solar cell.

Shockley Diode and DIAC:

it's kind of power diode that supports hysteresis phenomena . you can see the whole topic here Thyristor | Shockley Diode and DIAC

Silicon Controlled Rectifier (SCR) and TRAIC:

it similar to Shockley diode with gate terminal added . you can see the whole topic here Thyristor | Silicon Controlled Rectifier (SCR) and TRIA

Transient Voltage Suppression Diode:

transient occur in circuit when a sudden change of voltage occur this transient may damage circuit component, this kind of diode can avoid that 

so it's kind of protection component.

this diode can provide high impedance in normal operation and doesn't affect the current flow of circuit but when sudden spike occur it has very fast response and starts to enter the avalanche breakdown state  providing  very low impedance and reduce voltage to normal. 

Zener Diode:

as mentioned before diode allow current in one direction but in case of zener diode it also allow the other direction.

in reverse bias there's a reference value of voltage called breakdown voltage as exceeding this value the diode conduct current.

there are many product of zener with different break down voltage. 

it used as over voltage protection and voltage regulation.

Schottky Diode:

It also called schottky barrier or hot carrier it formed by combination of semiconductor material and metal that's why this kind of diode has very low forward voltage rating reach 0.15 , high current rating , low power consumption and very fast switching action.

it can used as voltage clamping and high frequency rectifier application.