Explain junction transistors (npn and pnp), Electrical Engineering

Assignment Help:

Explain junction transistors (npn and pnp).

Junction Transistor:

This transistor consists of two p-n junctions combined in one crystal as demonstrated in figure below.

710_npn and pnp.png

There are two major forms of junction transistors depending on whether the middle section is on a p material or an n material. The middle sector is termed as the base and the outer regions are termed as the emitter and the collector correspondingly.

The transistor is a 3-terminal device and its properties may be given in terms of characteristic curves involving the three currents and the three voltages demonstrated in figure below.

521_3 terminal device of transistor.png

Within a transistor there is zero resultant current of electrons and holes across all junctions. If the collector is connected directly to the base and a small positive voltage is applied among emitter and base after that a current flows just as in a p-n junction diode in the forward direction. Likewise if the emitter is joined to the base and a negative voltage is applied in between collector and base, current flows in the reverse direction, demonstrating a saturation of collector current.

These voltages with similar polarity are applied simultaneously as demonstrated in figure below.

2109_voltages with similar polarity in transistor.png

The potential barrier in between base and emitter is decreased and the flow of holes across the barrier greatly rises. There is an increased flow of electrons from base to emitter but because the hole density in the p- region is much higher than the electron density in the n- area, the current may be seem to be mainly because of the holes. The holes enter the n- region and diffuse by this, and combine with the electrons in that area as the base region is made sufficiently thin, many of holes reach the collector and base junction and very little arrive at the base terminal. Holes fall easily into the collector region on account of field at the collector base junction. Therefore the collector current is very nearly equivalent to the emitter current and the base current is almost zero. VCB has little effect on the current as long as its magnitude is above various minimum values and the base is adequately thin. A small change in VEB causes a change in IC resulting in an approximately equal change in IC.


Related Discussions:- Explain junction transistors (npn and pnp)

Semiconductor in equilibrium, Semiconductor  in Equilibrium Equilib...

Semiconductor  in Equilibrium Equilibrium in semiconductors implies the following: (i) Steady state: ∂Z / ∂t = 0 In which Z is any physical quantity like charge, volt

Calculate load current and terminal voltage of each machine, Q. The externa...

Q. The external - characteristics data of two shunt generators in parallel are given as follows: Load Current, A: 0 5 10 15 20 25 30 Terminal voltage I, V: 270 263 254 240 22

Differential amplifier, Ask question #Minimum 100 words What is neeed of d...

Ask question #Minimum 100 words What is neeed of differential amplifier

What are synchronous decade counters, What are Synchronous Decade Counters?...

What are Synchronous Decade Counters? Alike to an asynchronous decade counter, the synchronous decade counter counts from 0 to 9 and then recycles to 0 again, This is done by

Solid mensuration, reflections, journey about the subject solid mensuration...

reflections, journey about the subject solid mensuration

Commercial fm radio broadcasting, Q. Commercial FM radio broadcasting? ...

Q. Commercial FM radio broadcasting? Commercial FM radio broadcasting utilizes the frequency band of 88 to 108 MHz for the transmission ofmusic and voice signals. The carrier

Find the new direct transfer gain, A voltage amplifier without feedback has...

A voltage amplifier without feedback has a nominal gain of 500. The gain, however, varies in the range of 475 to 525 due to parameter variations. In order to reduce the per-unit ch

Discuss important properties and uses of rubber, Discuss important properti...

Discuss important properties and uses of Rubber. Rubber: It is polymeric material along with high elastic yield strain. The various types of rubber materials are given as-

Explain iron and silicon iron alloys, Explain iron and silicon iron alloys....

Explain iron and silicon iron alloys. Iron: Galvanised steel and iron wires that are usually used for earth conductor in low voltage distribution systems may also be utilize

Discuss important properties and uses of ceramics, Discuss important proper...

Discuss important properties and uses of Ceramics. Ceramics - These are materials made by high temperature firing treatment of natural clay and specific inorganic matters. The

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd