Example-2:

For the circuit show in fig. 6, it is given that β =100, V_BE =0715V. Determine

• The dc conditions for each state
• The overall voltage gain
• The maximum peak to peak output voltage swing.

Fig. 6

Solution:

(a). The base currents of transistors are neglected and V_BE drops of all transistors are assumed same.

From the dc equivalent circuit,

and

b) The overall voltage gain of the amplifier can be obtained as below:

Therefore, voltage gain of second stage

The input impedance of second stage is

The effective load resistance for first stage is

Therefore, the voltage gain of first stage is

The overall voltge gain is A_V = A_V1 A_V2

(c). The maximum peak to peak output votage swing = Vopp = 2 (V_C7 - V_E7)
                                                                                                = 2 x (5.52 - 3.325)
                                                                                                = 4.39 V

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