A common-emitter transistor amplifier has a collector load of 10 kΩ. If its h_fe = 100  and h_ie = 2 kΩ (h_re ≈ h_oe ≈ 0), the voltage amplification of the amplifier is nearly equal to

Concept:

Voltage gain is for CE configuration amplifier is given as:

  -----(1)

Where hie = Input impedance

hre = reverse voltage gain

hfe= forward current gain

h0e = output conductance

Calculation:

Given:

hfe = 100  

hie = 2 KΩ 

RL' = 10 KΩ 

From equation (1):

|AV| = 500

Derivation:

Representing Transistor with approximate Common Emitter h parameter model and neglecting h_oe.

A_I (current gain) is given as the ratio of load current to the input current.

using current divider between R_L' and 1/h_oe

 ----(2)

Now Voltage gain can be calculated as:

From equation (2), putting the value of A_I  in the above equation:

Important Points

Input Impedance (R_I) = h_ie + h_reR_L'A_I

Output Resistance (R₀):