1. 2 3 Low frequency modelHigh frequency model C π is the capacitance of the forward-biased BE...
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Transcript of 1. 2 3 Low frequency modelHigh frequency model C π is the capacitance of the forward-biased BE...
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Low frequency model High frequency model
Cπ is the capacitance of the forward-biased BE junction Cμ is the Capacitance of the reverse-biased BC junction The value of Cμ is usually much smaller than Cπ
typical circuit parameter values of Cμ = 0.02 pF and Cπ = 0.2 pF
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The common emitter amplifier has a high gain. (advantage)ButIt has limited bandwidth (FH-FL). Its FH is not that large.(disadvantage)
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The cascode amplifier has a high gain. (advantage)It has higher bandwidth (FH-FL) than that of common emitter amplifier .
Its FH is large.(advantage) Why?!!!!!!!
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The CE amplifier has only two internal capacitances, the cascode amplifier has four internal capacitances. Since FH is inversely proportional to internal capacitors, CE should have higher FH.
Noooooooooooooo, Why?
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Cπ doesn't suffer from miller effect sine it has a Ground terminal
C suffers from miller effect
The values of K about (-100 to -400)
C1 becomes from (100 to 400)C
The high value of C1 makes FH limited
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Cπ1 , Cπ2 , and Cdoesn't suffer from miller
C suffers from miller effect
C1 and C2 become equal 2C
FH is large
effect because of the Ground terminal
Small values of internal capacitors and small millereffect
smaller miller effect