1

GATE ECE 2001

Subjective

+5

-0

An emitter-follower amplifier is shown in the figure, Z

_{i}is the impedance looking into the base of the transistor and Z_{0}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 z_{i}.

(c)Obtain an expression for z_{0}.

2

GATE ECE 2000

Subjective

+5

-0

For the amplifier of given figure,

$${I_C}\, = \,1.3\,mA,\,{R_C}\, = \,2\,k\Omega ,\,{R_E}\, = \,500\,\Omega ,$$

$${V_T}\, = \,26\,mV,\,\beta \, = \,100,\,{V_{CC}}\, = \,15V,$$

$${V_s}\, = \,0.01\,\sin \left( {\omega t} \right)\,V\,and\,{C_b}\, = \,{C_C}\, = \,10\,\mu F.$$

$${I_C}\, = \,1.3\,mA,\,{R_C}\, = \,2\,k\Omega ,\,{R_E}\, = \,500\,\Omega ,$$

$${V_T}\, = \,26\,mV,\,\beta \, = \,100,\,{V_{CC}}\, = \,15V,$$

$${V_s}\, = \,0.01\,\sin \left( {\omega t} \right)\,V\,and\,{C_b}\, = \,{C_C}\, = \,10\,\mu F.$$

(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 I

_{bias}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 (R_{1}, and output resistance (R_{0}) of the circuit. Assume $${V_{T\,\,}} = \,\,26\,mV.$$

4

GATE ECE 1998

Subjective

+5

-0

In the circuit of fig. Determine the resistance R

_{o}seen by the output terminals, ignore the effects of R_{1}and R_{2}.Questions Asked from Bipolar Junction Transistor (Marks 5)

Number in Brackets after Paper Indicates No. of Questions

GATE ECE Subjects

Signals and Systems

Representation of Continuous Time Signal Fourier Series Fourier Transform Continuous Time Signal Laplace Transform Discrete Time Signal Fourier Series Fourier Transform Discrete Fourier Transform and Fast Fourier Transform Discrete Time Signal Z Transform Continuous Time Linear Invariant System Discrete Time Linear Time Invariant Systems Transmission of Signal Through Continuous Time LTI Systems Sampling Transmission of Signal Through Discrete Time Lti Systems Miscellaneous

Network Theory

Control Systems

Digital Circuits

General Aptitude

Electronic Devices and VLSI

Analog Circuits

Engineering Mathematics

Microprocessors

Communications

Electromagnetics