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3 Low frequency modelHigh frequency model C π is the capacitance of the forward-biased BE junction C μ is the Capacitance of the reverse-biased BC junction The value of C μ is usually much smaller than C π typical circuit parameter values of C μ = 0.02 pF and C π = 0.2 pF

4 The common emitter amplifier has a high gain. (advantage) But It has limited bandwidth (F H -F L ). Its F H is not that large.(disadvantage)

5 The cascode amplifier has a high gain. (advantage) It has higher bandwidth (F H -F L ) than that of common emitter amplifier. Its F H is large.(advantage) Why?!!!!!!!

6 The CE amplifier has only two internal capacitances, the cascode amplifier has four internal capacitances. Since F H is inversely proportional to internal capacitors, CE should have higher F H. Noooooooooooooo, Why?

7 Also we call this as miller effect. As K increases this will lead C 1 to be large

8 C π 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) C 1 becomes from ( 100 to 400) C  The high value of C 1 makes F H limited

9 C π1, C π2, and C   doesn't suffer from miller C  suffers from miller effect C 1 and C 2 become equal 2 C  F H is large effect because of the Ground terminal Small values of internal capacitors and small miller effect smaller miller effect

 Both the C.E. and Cascode amplifiers almost have the same A m, R in, R out and F L, But 10 C.E. Cascode

11  Measure: 1- A M 2-R IN (Use R D = 1 kΩ) 3-R O (Use R D = 1 kΩ) 4-F L 5-F H Experimentally

12  Measure: 1- A M 2-R IN (Use R D = 1 kΩ) 3-R O (Use R D = 1 kΩ) 4-F L 5-F H