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)

Interpoles, These are small poles fixed to the yoke and spaced in b/w the m...

These are small poles fixed to the yoke and spaced in b/w the main poles. They are wound with comparatively few heavy gauge Cu wire turns and are connected in series with the armat

#DSP ., #The requirement is as follows- There is a signal which is in the r...

#The requirement is as follows- There is a signal which is in the range of 0 to 5Hz. This signal frequency composition is to determined. The resolution of the determination is 1Hz.

Determine the performance of the circuits, With the development of cheap an...

With the development of cheap and reliable operational amplifiers the need to design amplifier circuits has disappeared. However it is still necessary to utilise these devices in a

Find the efficiency of the transformer, Q. Athree-phase, 600-kVA, 2300:230-...

Q. Athree-phase, 600-kVA, 2300:230-V,Y-Ytrans- former bank has an iron loss of 4400 W and a full- load copper loss of 7600 W. Find the efficiency of the transformer for 70% full lo

Compare call and push instructions, Compare CALL and PUSH instructions ...

Compare CALL and PUSH instructions CALL PUSH When CALL is implemented the microprocessor automatically stores the 16-bit address of the instruction next to CALL on the sta

Variable frequency systems , Variable Frequency  Systems In this  sys...

Variable Frequency  Systems In this  systems the chopping period  T will varying but  either Ton is kept constant or T off kept constant. In  any case the off  time T off   w

Field current and the armature terminal voltage, Consider the operation of ...

Consider the operation of a dc shuntmotor that is affected by the following changes in its operating conditions. Explain the corresponding approximate changes in the armature curre

What do you understand by dram and its refreshing, What do you understand b...

What do you understand by DRAM and its refreshing? Dynamic RAM (DRAM) is fundamentally the same as SRAM, but this retains data for only 2 or 4 ms on an internal capacitor. But

Find the quantum levels, A uniform quantizer is said to have 16 levels, and...

A uniform quantizer is said to have 16 levels, and hence is called a midriser. The saturation levels are to correspond to extreme values of the message of 1 V ≤  f(t) ≤ 17 V. Find

Measurment, emitter followers regulator

emitter followers regulator

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