1
GATE ECE 2001
Subjective
+5
-0
An emitter-follower amplifier is shown in the figure, Zi is the impedance looking into the base of the transistor and Z0 is the impedance looking into the emitter of the transistor

(a)Draw the small signal equivalent circuit of the amplifier.
(b)Obtain an expression for zi.
(c)Obtain an expression for z0.

2
GATE ECE 2000
Subjective
+5
-0
For the amplifier of given figure,
$${I_C}\, = \,1.3\,mA,\,{R_C}\, = \,2\,k\Omega ,\,{R_E}\, = \,500\,\Omega ,$$
$${V_T}\, = \,26\,mV,\,\beta \, = \,100,\,{V_{CC}}\, = \,15V,$$
$${V_s}\, = \,0.01\,\sin \left( {\omega t} \right)\,V\,and\,{C_b}\, = \,{C_C}\, = \,10\,\mu F.$$

(a)What is the small-signal voltage gain, $${A_V} = {V_0}/{V_s}?$$
(b)What is the approximate $${A_{v,}}\,\,if\,\,{C_e}\,\,$$ is removed?
(c)What will $${V_0}\,be\,if\,{C_b}$$ is short circuited?

3
GATE ECE 1999
Subjective
+5
-0
A bipolar junction transistor amplifier circuit is shown in the figure. Assume that the current source Ibias is ideal, and the transistor has very large$$\beta ,\,\,{r_{b\,\,}} = \,\,0,$$ and the $${r_0}\, \to \,\infty$$.

Determine the ac small-signal mid-band and voltage gain $$\left( {{V_o}/{V_s}} \right),$$ input resistance (R1, and output resistance (R0) of the circuit. Assume $${V_{T\,\,}} = \,\,26\,mV.$$

4
GATE ECE 1998
Subjective
+5
-0
In the circuit of fig. Determine the resistance Ro seen by the output terminals, ignore the effects of R1 and R2.
EXAM MAP
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