An investigation of transistor current in npn and pnp bipolar junction transistors

This is all about difference between NPN and PNP transistors which are used to build many electrical and electronic projects. Bipolar Junction transistors are three terminal device and these are made of doped materials, often used in amplifying and switching applications.

NPN transistors can be used for these switches. A powerful electric signal turns the switch on, whereas a lack of a signal turns the switch off.

The structure of BJTs is such that a thin layer of P-type or N-type semiconductor material is sandwiched in between two layers of an opposite type semiconductor. The operation of these transistors involves both electrons and holes. The small current that controls the main current goes from base to emitter, or from emitter to base, once again depending on the kind of transistor it is PNP or NPN, respectively.

The schematic symbols are shown in Figure below a and d. When the transistor is switched on, the large current IC flows between the collector and emitter within the transistor. Since they are internally constructed very differently, current and voltage must be allocated differently in order for them to work.

The base-collector terminals of the PNP transistor are always reversed biased, then the negative voltage must be used for the collector.

Bipolar junction transistor

Conversely, the large, controlled current is referred to as the collector current because it is the only current that goes through the collector wire.

The heavy doping of the emitter region and light doping of the base region causes many more electrons to be injected from the emitter into the base than holes to be injected from the base into the emitter.

In operation, generally BE junction is forward biased and BC junction is reverse biased with a much higher voltage. A current at the base of the transistor allows for a much larger current across the emitter and collector leads.

And as you decrease current to the base of a NPN transistor, the transistor conducts current across from collector to emitter less and less, until the voltage supplied to the base is under the threshold voltage amount of 0.

Difference Between an NPN and a PNP Transistor

In analog circuit design, the current-control view is sometimes used because it is approximately linear. Also, the emitter voltage is positive with respect to the collector VCE.

In an NPN transistor, output current flows from the collector to the emitter. The characteristics of both PNP and NPN transistors are similar except that the biasing of the voltage and current directions are reversed for any one of the possible three configurations such as a common base CBcommon emitter CE and common collector CC.

Because, the transistor amplifying properties come from the consequent control that the base employs upon the collector to emitter current. These electrons diffuse through the base from the region of high concentration near the emitter toward the region of low concentration near the collector.

However, this only happens when a small biasing current Ib flows through the base terminal of the transistor. The functional difference between a PNP transistor and an NPN transistor is the proper biasing polarity of the junctions when operating.

This is the first and foremost rule in the use of transistors: This is called conventional current.The functional difference between a PNP transistor and an NPN transistor is the proper biasing (polarity) of the junctions when operating.

For any given state of operation, the current directions and voltage polarities for each kind of.

Introduction to Bipolar Junction Transistors (BJT)

NPN vs PNP Transistor. Transistors are 3 terminal semiconductor devices used in electronics. Based on the internal operation and structure transistors are divided into two categories, Bipolar Junction Transistor (BJT) and Field Effect Transistor (FET).

There are two basic types of transistors i.e. bipolar junction transistor or BJT and field effect transistor FET, that are used in two broad areas i.e. linear amplifier to boost or amplify an electrical signal and as an electronic switch.

NPN and PNP transistors are bipolar junction transistors, and it is a basic electrical and electronic component which is used to build many electrical and electronic projects.

The operation of these transistors involves both electrons and holes. The PNP and NPN transistors allow current amplification. The construction and terminal voltages for an NPN transistor are shown above.

The PNP Transistor has very similar characteristics to their NPN bipolar cousins, except that the polarities (or biasing) of the current and voltage directions are reversed for any one of the possible three configurations looked at in the first tutorial, Common Base, Common.

Difference Between NPN and PNP Transistor

A bipolar junction transistor (bipolar transistor or BJT) is a type of transistor that uses both electron and hole charge carriers. In contrast, unipolar transistors, such as field-effect transistors, only use one kind of charge carrier.

Differences between NPN & PNP Transistors and their Making Download
An investigation of transistor current in npn and pnp bipolar junction transistors
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