1

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 $${V_{T\,\,}} = \,\,26\,mV.$$

2

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}.3

GATE ECE 1997

Subjective

+5

-0

The transistor in the circuit shown in the figure. is so biased (dc biasing N/W is not shown) that the dc collector current I

_{C}= 1mA. Supply is V_{CC}= 5V.The N/W components have following values, R_{C} = 2$$k\Omega $$,

R_{S} = $$1.4k\Omega $$,

R_{E} = $$100\Omega $$.

The transistor has specifications, $$\beta \,\, = \,\,100$$

and base spreading resistance $${r_{bb\,}}^1\, = \,100\Omega $$

Evaluate input resistance R_{i} for two cases. At a frequency of 10 kHz

(a)C_{E}, the bypass capacitor across R_{E} is 25 $$\mu F$$

(b)The bypass capacitor C_{E} is removed leaving R_{E} unbypassed.

4

GATE ECE 1997

Subjective

+5

-0

In the cascade amplifier circuit shown below, determine the values of R

_{1}, R_{2}and R_{L}. Such that the quiescent current through the transistors is 1mA and the collector voltage V_{c1}= 3V, and V_{c2}= 6V. Tke V_{BE}= 0.7V, Transistor $$\beta $$ to be hifgh and base currents to be negligible.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 Discrete Time Signal Fourier Series Fourier Transform Discrete Time Signal Z Transform Continuous Time Linear Invariant System Transmission of Signal Through Continuous Time LTI Systems Discrete Time Linear Time Invariant Systems Sampling Continuous Time Signal Laplace Transform Discrete Fourier Transform and Fast Fourier Transform Transmission of Signal Through Discrete Time Lti Systems Miscellaneous Fourier Transform

Network Theory

Control Systems

Digital Circuits

General Aptitude

Electronic Devices and VLSI

Analog Circuits

Engineering Mathematics

Microprocessors

Communications

Electromagnetics