PN Junction Diode Working in Forward Biasing and Reverse Biasing by Shubham Kola
Subject - Basics of Electronics
Chapter - PN Junction Diode
Chapter - PN Junction Diode
Transcript
00:07In this video
00:08we’re going to learn
00:09Construction and Working
00:11of PN Junction Diode
00:13and its applications
00:14in real life
00:17the PN Junction diode
00:19are an important part of many devices
00:21you use every day
00:23like your phone charger
00:25or the circuits
00:26inside your home appliances
00:30by the end of this lesson
00:32you’ll understand
00:33how the PN Junction diode works
00:35and how it is used in real life
00:40first, let’s understand
00:41what a PN Junction diode is
00:44to do this
00:45we need to know
00:46two key terms
00:48that is P type material
00:50and N type material
00:53P type material
00:55imagine a material
00:57where there are some missing electrons
00:59creating “holes”
01:00where electrons could be
01:03these holes
01:04behave like positive charges
01:07because they attract electrons
01:10this type of material
01:12is called “P type material”
01:14because it has a positive nature
01:18N type material
01:20now, think of a material
01:21that has a few extra electrons
01:23these extra electrons
01:25can move around
01:26and carry a negative charge
01:29this material is called as
01:30“N type material”
01:32because it has a negative nature
01:36when we place
01:37P type material
01:38and N type material
01:40next to each other
01:42they form a PN Junction
01:45this junction creates a diode
01:48the diode is a device
01:50that allows electric current
01:52to flow
01:53in only one direction
01:54while blocking it in other direction
01:58So first we will see
01:59formation of PN junction
02:02when P type and N type materials
02:04come together
02:06something interesting happens at boundary
02:08called the junction
02:10at first
02:12electrons from the N type material
02:14move into P type material
02:16to fill the holes
02:18similarly
02:19holes from P type material
02:21move into N type material
02:24as electrons move into P type material
02:27they fill some holes
02:30and as holes move into N type material
02:32they leave behind negatively charged ions
02:36this movement of electrons and holes
02:39doesn’t continue forever
02:41soon,
02:42a region forms near the junction
02:44where there are no free electrons
02:46or holes
02:48this area is called as
02:50depletion region
02:51because it has no mobile charge carriers
02:56the depletion region
02:57act like a barrier
02:59that prevents
03:00further movement of electrons and holes
03:02across the junction
03:05it is like a "shield"
03:06that stops charges
03:08from freely moving across
03:13now we will see
03:14Working of a PN Junction diode
03:17now that we know
03:18what a PN Junction is
03:20let’s talk about
03:22how the diode works
03:23hen we apply an external voltage
03:28when you connect
03:28positive terminal of a battery
03:31to P type material
03:33and negative terminal of a battery
03:35to N type material
03:37you are "forward biasing"
03:38the diode
03:40in this condition
03:42the external voltage
03:43pushes electrons
03:45in N type material
03:46towards the junction
03:48and it pushes the holes
03:50in P type material
03:51towards the junction
03:53as well
03:55if the applied voltage
03:57is strong enough
03:58to overcome the barrier
03:59created by depletion region
04:02the electrons and holes
04:03can cross the junction
04:05and current flows through the diode
04:07the diode is "on"
04:09in this state,
04:10allowing electricity to pass
04:14if you reverse the battery connections
04:17positive to N type
04:18and negative to P type
04:20you are "reverse biasing" the diode
04:23in this case
04:25the external voltage
04:26pulls the electrons
04:28in N type material
04:29away from the junction
04:31and does the same
04:32to the holes
04:33in the P type material
04:36this action
04:37widens the depletion region,
04:39making it even harder
04:40for any charge carriers
04:42to cross the junction
04:44as a result,
04:45the diode blocks the flow of current,
04:47acting like an "off" switch
04:53now we will see
04:55real life applications
04:56of the PN junction diode
04:59the PN junction diode
05:01is not just a theoretical concept
05:03it’s used in many practical applications
05:06let’s look at some of these
05:09first is rectifiers
05:12one of the most common use
05:13of a diode
05:14is in converting AC current
05:16to DC current
05:18this process is known as
05:20rectification
05:23in devices like phone charger
05:25the AC from wall socket
05:27is converted into DC
05:29using diodes
05:32next is voltage regulation
05:34diodes are also used
05:35in voltage regulation circuits
05:37to maintain a constant output voltage
05:41zener diodes
05:42a special type of diode
05:44are designed to allow current
05:45to flow in the reverse direction
05:47when a certain voltage is reached
05:50this property is used
05:52to keep the voltage
05:53across a load constant
05:54protecting sensitive electron
05:56from voltage spikes
06:00Next is signal demodulation
06:03in radio receivers
06:05diodes are used
06:06to demodulate signals
06:08which means
06:09they helps in
06:10extracting the original information
06:12from a modulat carrier wave
06:15Next is protection circuits
06:17diodes are often used
06:19to protect circuits
06:20from voltage spikes
06:23for example
06:24flyback diodes
06:25are used in circuits
06:27with inductive loads
06:28like motors
06:29to prevent damage
06:30when the current is suddenly interrupted
06:34a light emitting diode
06:36LED
06:37is a special type of diode
06:39that emits light
06:40when current flows through it
06:41in the forward direction