HOW DO TRANSISTORS WORK??

 TRANSISTORS.....

So here again i'm back with a knowledgeable blog related to one more wonder in the world of electronics .i.e. "THE TRANSISTORS".

JUNCTION TRANSISTOR .

A junction transistor is formed by sandwiching a thin wafer of one type of semiconductor between two layers of another type . The  n-p-n transistor has a p type wafer between two n type layers . Similarly the p-n-p transistor has a n-type wafer between two p-type layers.

 (i) p-n-p transistor : 

 

working: let us consider pnp transistor in common base mode.Since emitter-base is forward biased holes move toward base. Few of them combine with electrons in the base and  rest go to the collector .Since base-collector is reverse biased holes coming from base move toward the terminal of collector . They  combine with equal number of electrons entering from collector terminal

(ii) n-p-n transistor:                                                 

 

working:A common base circuit of an n-p-n transistor .Majority charge carriers in the emitter (n-type) are electrons .Since , emitter-base circuit is forward biased .The electrons rush from emitter to base .Few of them leave the base terminal (comprising Ib )and rest move to the collector .These electrons finally leave the collector finally leave the collector terminal (give rise to Ic). Electrons coming from base and from collector meet at junction O and they jointly move to emitter ,which gives rise to Ie .

(a) p-n-p transistor 

(b) n-p-n junction.

Various Applications and Uses of Transistor

• The core use of transistors include switching applications or both as amplification and switching.

• There is a kind of transistors which produce current flow depending on the amount of light shined upon them, those are known as phototransistors.

• Bipolar Junction Transistors(BJT) can cause a greater current flow from the emitter to collector when a small amount of current is passed through the base.

• Field Effect Transistors acts as voltage controlled devices. Field Effect Transistors (FETs) have very high input impedance and it helps to run very little current through them. This is helpful for not causing the power source to load down as they are not disturbing the original circuit power elements on which they are connected to. FETs are cheaper and easier to manufacture and cause less loading.

• Heterojunction Bipolar Transistors (HBT) can provide faster switching speeds and is used in analog and digital microwave applications. They are priceless to fabricate and can provide better lithographic yield. They are used in mobile and laser drivers as power amplifiers.

• Darlington Transistors has much higher ability to gain current. Because of its sensitivity, it can pick currents from human skin and that is why it is used in creating a touch-sensitive button.

• Schottky Transistors diverts high input currents and prevents the transistors from saturating.

• Multiple Emitter Transistors are used in Transistor-Transistor Logic (TTL) and NAND logic gates.

• Dual Gate MOSFETs are used in RF mixers/multipliers, RF amplifiers where two controlled gates are required in a series.

• Avalanche Transistors has the capability of switching high currents in less than nanosecond transition times.