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Bipolar Junction Transistors (BJTs). Bipolar. Two. Polarity. Transistor. Resistor. Tranfer. +. Types of BJTs. NPN PNP. p-type. n-type. n-type. NPN-BJT Structure. C. B. E. NPN BJT Symbol. n-type. p-type. p-type. PNP-BJT Structure. C. B. E. PNP BJT Symbol.
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Bipolar Junction Transistors (BJTs) Bipolar Two Polarity Transistor Resistor Tranfer +
Types of BJTs • NPN • PNP
p-type n-type n-type NPN-BJT Structure
C B E NPN BJT Symbol
n-type p-type p-type PNP-BJT Structure
C B E PNP BJT Symbol • Emitter is reversed
E Base (p-type) C Emitter (n-type) Collector (n-type) B Current Flow Convention IE IC IB
BJT structure note: this is a current of electrons (npn case) and so the conventional current flows from collector to emitter.
Transistor Connections • Common Base Connection • Common Collector Connection • Common Emitter Conncetion
Current Amplification Factor α =IC / IE ( constant VCB) • The value of α is lies b/w 0.9 to 0.999 • Total collector current • IC=αIE+Ileakage
Current Amplification Factor • γ = IE/IB • Expression for collector current. • IC= IB /1-α+ ICBO /1-α
Base Current Amplification Factor • β= IC / IB • The range of β is 20 to 500. • Expression for collector current. • IC= βIB + ICEO