TRANSISTOR:
A transistor has three-layer semiconductor device consisting of either two n- and one p-type layers of material or two p- and one n-type layers of material. The former is called an npn transistor, while the called an pnp transistor.
There are two kinds of transistor.
1. P-N-P transistor
2. N-P-N transistor
Working of N-P-N transistor:
The n-p-n transistor with forward bias to emitter bias junction and reverse bias to collector-bias junction. The forward bias causes the electron in the n-type emitter to flow towards the base. This constitutes the emitter current IE . As these electrons flow through the P-type base, they tend to combine with hole. As the base is lightly doped and very thin, therefore, only a few electrons combine with holes to constitute base current IB . In this way entire emitter current flows in the collector circuit. The emitter current is the sum of collector and base current I, e. IE = IB + IC Working of P-N-P transistor:
Bipolar Junction Transistor:
A bipolar junction transistor (BJT) is widely used in discrete circuits as well as in IC design, both analog and digital. Its main applications are in amplification of small signals, and in switching digital logic signals. In a BJT, both majority carriers and minority carriers play a role in the operation of the transistor, hence the term bipolar.
A transistor has three-layer semiconductor device consisting of either two n- and one p-type layers of material or two p- and one n-type layers of material. The former is called an npn transistor, while the called an pnp transistor.
1. P-N-P transistor
2. N-P-N transistor
Working of N-P-N transistor:
The n-p-n transistor with forward bias to emitter bias junction and reverse bias to collector-bias junction. The forward bias causes the electron in the n-type emitter to flow towards the base. This constitutes the emitter current IE . As these electrons flow through the P-type base, they tend to combine with hole. As the base is lightly doped and very thin, therefore, only a few electrons combine with holes to constitute base current IB . In this way entire emitter current flows in the collector circuit. The emitter current is the sum of collector and base current I, e. IE = IB + IC Working of P-N-P transistor:
The basic connection of p-n-p transistor. The forward bias causes the electron in the p-type emitter to flow towards the base. This constitutes the emitter current IE . As these holes cross into n-type base, they tend to combine with electrons. As the base is lightly doped and very thin, therefore, only a few holes combine with electrons to constitute collector region to collector current IC . In this way entire emitter current flows in the collector circuit. The emitter current is the sum of collector and base current .
Bipolar Junction Transistor:
A bipolar junction transistor (BJT) is widely used in discrete circuits as well as in IC design, both analog and digital. Its main applications are in amplification of small signals, and in switching digital logic signals. In a BJT, both majority carriers and minority carriers play a role in the operation of the transistor, hence the term bipolar.
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