Skip to main content

Featured post

Surge Protector Installation Best Approach

Post a Comment

DIODES

Diodes are two-terminal semiconductor device that allows current to flow only in one direction.
Because of the depletion layer created in between the PN-junction of the diode a voltage greater than the potential has to be applied between the 2-terminal of the diode to get it to the depletion zone.
This voltage is 0,7v for a Silicon type diode and 0.3v for a germanium type diode. This however means  that a diode will not conduct immediately in a circuit when a voltage is first apply to it.

It will only conduct when the potential voltage of or greater than 0.7v is supply to it.

 Forward Biased
A diode in the forward biased mode allows current to flow freely in a circuit




Reversed  Biased 
A diode in the reversed biased mode does not allow current flow, it blocks the flow of current in a circuit because the voltage applied to the diode is of opposite polarity. However, all diodes have a characteristics known as the breakdown voltage.

Also, when diode is connected in the reverse biased mode, majority carriers migrate towards the opposite side of the power supply (positive and negative side terminal) leaving behind a large depletion layer.
Notice also the migration of the minority charge carrier to the depletion layer.

 The breakdown voltage of the diode is the minimum reverse voltage that makes the diode conduct appreciably in reverse.When this reverse voltage is greater and have exceeded the actual/normal breakdown voltage of the diode as specified on the diode datasheet, the diode will breakdown and current will flow through the diode in the reverse direction.
Breakdown occurs the reverse voltage as increased beyond limit which enables the minority carrier overcome the potential barrier created by the depletion region of the diode.
Reverse voltage of diodes varies depending on the type and size.
At this point the diode act like a wire
NOTE: Breakdown of diode only occurs when applied voltage is greater than the rated reverse voltage of the diode as specified on the diode datasheet. 


Comments

Post a Comment

Popular posts from this blog

Nigeria Electrical Engineering Polytechnics Syllabus as specified by UNESCO

As session begins in most Nigerian university, polytechnics and colleges of education. It is thus advisable for students to keep there self updated and alert for urgent tests and exam as might be decided by the lecturer. UNESCO in a brief UNESCO is responsible for coordinating international cooperation in education, science, culture and communication. It strengthens the ties between nations and societies, and mobilizes the wider public so that each child and citizen: • has access to quality education; a basic human right and an indispensable prerequisite for sustainable development; • may grow and live in a cultural environment rich in diversity and dialogue, where heritage serves as a bridge between generations and peoples; • can fully benefit from scientific advances; • and can enjoy full freedom of expression; the basis of democracy, development and human dignity. UNESCO's messages are of increasing importance today, in a globalized world where i...
21 comments
Read more

Earthed and Unearthed System

Methods of Earthing In theory, the main power network does not have to be earthed and sometimes arguments are put forward that an unearthed network may be more reliable. In some cases this can be true, but generally an unearthed networks can be unreliable due to influence of electrical or some other factors. There are a number of ways in which an electrical power system can be operated – - Unearthed or insulated system - High impedance earthed and - Low impedance earthed arrangement Unearthed system/IT earthing system In this kind of installation, there is no formal connection to earth because there may be some high impedance connections for instrumentation e.g coil of a measuring device. Earthed vs Unearthed Electrical cable In some generators and transformers, the star point is solidly grounded. This is called Earthed Electrical system. In a three phase earthed system, phase to earth is 1.732(sqrt 3) is solidly earthed system higher than phase to phas...
Post a Comment
Read more

HND Electrical Engineering Syllabus

Hi my people, here is the list of courses you should be expecting when you are thinking of going for HND program in the polytechnics and 300/400 of a university degree. These ebooks comply with all the courses you might encounter during the pursuit of your bachelor's degree certificate and will be efficient and useful after the completion of your degree probably for advance and practical level. Download to view the course outline here - HND Electrical Engineering Course Outline  1. MTH 311 - Advance Algebra You can also get the whole mathematics pdf/ebook here All mathematics ebook 2. Engineering in Society MEC311 - Engineers in Society , Engineers in Society II 3. Electrical Measurement and Instrumentation EEC311 - Electrical Measurement and signal processing ,  Principles of Electrical Measurement 4.  Electrical Material Science EEC315 -  Electrical Material Science 5. Electrical Circuit Theory EEC 313 -  Electrical circuit theory revised secon...
5 comments
Read more