Lecture22

base current ib is small but its there sign of

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Unformatted text preview: s swept from thermal generation in reverse biased CB junction. + - Base current IB is small, but it’s there. Sign of IB goes against IC IE - + IB the direction of electron injection (see figure). There are both PNP and NPN bipolar transistors. In a well-designed BJT, IE ≈ IC ≈ 100IB We can write from current continuity: __________________ It’s easier to study PNP’s because current flows in direction of injected holes. But NPN is similar,Ijust IC holes with I = B + replace ………(KCL) Illinois ECE440 Prof. Eric Pop E 5 electrons, and keep good track V signs. + V ……… (KVL) of = V EC EB BC There are both PNP and NPN bipolar transistors. Intuitively (dimensions/doping being equal) which kind of bipolar transistor is faster? It’s easier to study PNP’s because current flows in direction of injected holes. But NPN is similar, just replace holes with electrons, and keep good track of signs. EE 332 Spring 2013 B BJT Structure JT Structure IE=IB+IC VEB+VBC+VCE=0 EE 332 Spring 2013 I Ep I En Ease transport factor: mitter efficiency: B BJT Performance Parameters B I C / I Ep y: Emitter Efficiency: sfer ratio: Current tran y: ncy: I Ep I Ep I En I Ep IC IBase transport factor: B Ep IE I Ep IIEpn E Ep I En I B I C / I Ep C I En actor: I Ep urrent amplification (common emitter gain): Base transport factor: actor: / I Ep IC t factor:B I C Current transfer ratio: B I C / I Ep I B 1 ratio: B I C / I Ep I B transfer r...
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This document was uploaded on 02/18/2014.

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