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ICO – IC current with emitter terminal open and is called leakage current.The comprises of two components – the majority and minority carriers IC = ICmajority + ICOminority.Applying KCL to the transistor : IE = IC + IB.Majority carriers can cross the reverse-biased junction because the injected majority carriers will appear as minority carriers in the n-type material.The large number of majority carriers will diffuse across the reverse-biased junction into the p-type material connected to the collector terminal.Resulting IB is typically in order of microamperes. A very small number of carriers (+) will through n-type material to the base terminal.Majority carriers (+) will diffuse across the forward-biased p-n junction into the n-type material.Both biasing potentials have been applied to a pnp transistor and resulting majority and minority carrier flows indicated.One p-n junction of a transistor is reverse-biased, whereas the other is forward-biased.The operation of the pnp transistor is exactly the same if the roles played by the electron and hole are interchanged. The basic operation will be described using the pnp transistor.It can be conclude that the work of transistor is base on work of diode.By imaging the analogy of diode, transistor can be construct like two diodes that connetecd together.

The arrow is always drawn on the emitter -The arrow always point toward the n-type -The arrow indicates the direction of the emitter current: pnp:E B npn: B E IC=the collector current IB= the base current IE= the emitter current

The emitter and collector terminals are made of the same type of semiconductor material, while the base of the other type of material.

Base is located at the middle and more thin from the level of collector and emitter.

Position of the terminals and symbol of BJT.

Thus, a two-pn-junction device has four types of bias.

A single pn junction has two different types of bias:.

The term bipolar reflects the fact that holes and electrons participate in the injection process into the oppositely polarized material.

2 p- and 1 n-type layers of material pnp transistor.

2 n- and 1 p-type layers of material  npn transistor.

3 layer semiconductor device consisting:.

BJT consists of three terminal:  collector : C  base : B emitter : E.

It can be use as amplifier and logic switches.

The famous and commonly use of this device is BJTs (Bipolar Junction Transistors).

The basic of electronic system nowadays is semiconductor device.

Bipolar Junction Transistor (BJT) - Next Slide