14 BJT Small Signal Analysis

14 BJT Small Signal Analysis - 1 npn / pnp Transistor Basic...

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Unformatted text preview: 1 npn / pnp Transistor Basic Principle DC Biasing Circuits ac Signal Circuits ac Equivalent Transistor Model ac Small-Signal Analysis 2 → S uperposition What next ?? Thevenin’s /Kirchhoff’s Theorem ac Equivalent Transistor Model Hybrid Equivalent Model r e Equivalent Model Small-signal Analysis Z i , Z o , A i , A v 3 4 5 (3) Voltage Gain ( A v = v o / v i ) :- C ie fe ie b C b fe i o v R h h h i R i h v v A - = × ×- = =- ve ⇒ π phase shift between v i and v o (4) Current Gain ( A i = i o / i i ):- b fe c o i h i i = = ( ) ( ) ie i b h R R R R i i + = 2 1 2 1 // // ( ) ( ) ie fe i o i h R R R R h i i A + = = 2 1 2 1 // // Phase Shift ?? R 1 // R 2 +- +- v i R C b e c i b i c v out i i h fe i b h ie R 1 // R 2 +- +- v i R C b e c i b i c v out i i h fe i b h ie i o I 6 or (4) Current Gain A i :- = + = + = + = ie i ie i ie i i b i h R R v h R R v h v R R v i I i // // 1 1 // 1 // 2 1 2 1 2 1 + = + = + = ie fe o ie ie b ie ie i i h R R h i h h R R i h h R R v i 1 // 1 1 // 1 1 // 1 2 1 2 1 2 1 ( ) ( ) 2 1 2 1 1 2 1 // // 1 // 1 R R h R R h h R R h h i i A ie fe ie ie fe i o i + = + = =- R 1 // R 2 +- +- v i R C b e c i b i c v out i i h fe i b h ie i o I 7 8 Example - Common-Emitter (Fixed-Bias) Configuration : Same as before!! B e B ie i i i R r R h i v Z // // β = = = C x o o R i v Z = = C e C ie fe i o v R r R h h v v A - = - = = β β B e B...
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This note was uploaded on 01/11/2011 for the course EE 2106 taught by Professor Ytchow during the Spring '07 term at City University of Hong Kong.

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14 BJT Small Signal Analysis - 1 npn / pnp Transistor Basic...

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