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)

Magnetic contactor, how to wire a three phase contactor to become a single ...

how to wire a three phase contactor to become a single phase contactor?

Can you explain honorarium?, Can you explain Honorarium? Ans: Honora...

Can you explain Honorarium? Ans: Honorarium is a remuneration for work performed which is intermittent or occasional in character and either so laborious or of such special

Solve the nonlinear equation and find r, Q. An interface circuit consisting...

Q. An interface circuit consisting of R 1 and R 2 is designed between the source and the load, as illustrated in Figure such that the load sees a Thevenin resistance of 50  betw

How the interrupts can be masked in 8086, How the interrupts can be masked/...

How the interrupts can be masked/unmasked in 8086? The 8086 interrupt priorities are concerned; software interrupts have the highest priority, followed by NMI followed by INTR.

State value of current flowing in the winding, The winding of an electromag...

The winding of an electromagnet has an inductance of 3H and a resistance of 15?. When it is connected to a 120 V d.c. supply, Determine: (a)  the steady state value of current f

8085 and 8086 in microprocessor, What is the difference among 8085 and 8086...

What is the difference among 8085 and 8086 in microprocessor? Ans) 8086 has a special concept known as memory segmentation. It permits parallel processing, whereas 8085 does no

Assinment, Ask question #Minimum mechanism of microwave communication 100 w...

Ask question #Minimum mechanism of microwave communication 100 words accepted#

Electromagnetic torque, The torque produced by each conductor in the field ...

The torque produced by each conductor in the field will be:  where A is the area of the armature winding in the magnetic field, Ia is the current in armature winding, and B

Set up a table for a 4-to-10 line excess-3 decoding, Q. (a) Excess-3 cod...

Q. (a) Excess-3 code is a 4-bit binary code for the 10 decimal digits and is found useful in digital computer arithmetic. Each combination is found by adding 3 to the decimal nu

Voltage tripler and quadrupler, Voltage Tripler and Quadrupler: Voltag...

Voltage Tripler and Quadrupler: Voltage Tripler an extension of the half wave voltage across each diode is 2Vm as it is for the filter capacitor circuit. It should be obvious

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