Mansoura University
Faculty of Engineering
Communication Engineering Department
Second Year Communication
Microelectronic Circuits
Sheet (4)
[1] For the emitter follower (Common collector) in Fig.1, the signal source is
directly coupled to the transistor base. Assume β = 100 and neglect ro. Find
the Following:
(a) The dc emitter current.
(b) The Input Resistance Rin.
(c) The voltage gain vo/vsig.
(d) The current gain io/ii.
(e) The output resistance Rout.
[2] For the emitter-follower circuit shown in Fig. 2. For the two values of β (β
= 40 and β = 200), find:
(a) IE, VE, and VB.
(b) The input resistance Rin.
(c) The voltage gain vo/vsig.
[3] The amplifier of Fig.3 consists of two identical common-emitter amplifiers
connected in cascade. Observe that the input resistance of the second stage,
Rin2, constitutes the load resistance of the first stage.
(a) For Vcc = 15 V, Rl = 100 kΩ, R2 = 47 kΩ, RE = 3.9 kΩ, Rc = 6.8 kΩ, and
β = 100, determine the dc collector current and dc collector voltage of
each transistor.
(b) Draw the small-signal equivalent circuit of the entire amplifier. Neglect
ro1 and ro2.
(c) Find Rinl and vbl/vsig for Rsig = 5 kΩ.
(d) Find Rin2 and vb2/vbl.
(e) For RL = 2 kΩ, find vo/vb2.
(f) Find the overall voltage gain vo/vsig.
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Mansoura University
Faculty of Engineering
Communication Engineering Department
Second Year Communication
Microelectronic Circuits
Sheet (4)
Fig.1
Fig.2
Fig.3
Page 2