ISRO Scientist/Engineer ECE Solved Papers

Two systems $h_1[n] = A(b_1)^n u[n]$ and $h_2[n] = A(b_2)^n u[n]$ are cascaded. If the effective $H(z) = \frac{4}{4 - z^{-2}}$, find a possible value of $(A, b_1, b_2)$:

The inputs to a digital circuit are signals $A, B$ and $C$. $\overline{A}$, $\overline{B}$ and $\overline{C}$ are not available. The $+5\text{V}$ supply and the ground can be used as logic '1' and '0' inputs respectively. To implement a function $\overline{B}\overline{C} + A\overline{C}$ using only 2:1 multiplexer, minimum number of MUX required is:

Which of the following is not true in VHDL?

A 4-bit unipolar DAC with $10\text{V}$ reference is fed to the input of a comparator, whose threshold is set as $7.5\text{V}$. When the DAC counts from 0 and reaches 8, the comparator showed threshold crossing wrongly. It is found that one of the DAC input bit is stuck at '1'. Which is the stuck at '1' bit?

Resistors $R_1, R_2$ and $R_3$ are connected in series across a voltage source $V$ and $R_4$ is connected in parallel with $R_3$. $R_1$ to $R_4$ are to be chosen from available resistor values $3\ \Omega, 6\ \Omega, 10\ \Omega$ and $15\ \Omega$. What will be the ratio of maximum current to minimum current through $R_1$ by choosing resistor values appropriately?

A system is defined by the difference equation:

then the system is:

The state transition diagram for the circuit given below is:

Given a single 3:8 active high output decoder. What is the minimum number of 3-input OR gates required to implement a one bit Full adder?

In the given figure, find the value of $(X_0, X_1, X_2, X_3, X_4, X_5, X_6, X_7)$ to realise the function $F = A + \overline{B}$ using two 4:1 multiplexers (with select inputs $S_1 = A, S_0 = C$) and one 2:1 multiplexer (with select input $B$):

Which of the following is True for signal travelling through a Wave-Guide?

For matched junction S parameters, which of the following is correct?

Which of the following transmission modes is supported by Stripline?

For a directional coupler, if $P_i = \text{Incident Power}$, $P_o = \text{Output power}$, $P_f = \text{Forward coupled power}$ and $P_r = \text{Reverse coupled power}$; then, Directivity of directional coupler is:

Magic Tee can produce:

The cut off frequency of TEM wave is:

In transistor oscillators, FET and BJT are used. Instability is achieved by:

In a three stage cascade amplifier, each stage has a gain of $10\text{ dB}$ and noise figure of $10\text{ dB}$. The overall noise figure is:

Operating Frequency limitation for Bipolar semi-conductor device is due to

Which of the following offers highest speed of operation?

Gunn Diode operated at a high frequency is a

Compared to Silicon, GaAs Semi-conductors offer advantage of:

Calculate the approximate power added efficiency of following power amplifier:

• DC Voltage: $8\text{ volts}$
• DC Current: $5\text{ Amp}$
• AC Input signal: $0\text{ dBm}$
• O/P power: $30\text{ dBm}$

Which of following class of amplifiers provides highest efficiency?

Compared to Linear power supplies SMPS offers

What are the different circuit topologies used for DC/DC converter designs?