$$1 cm^{3}$$ of pure Germanium at $$20^\circ$$C contains about $$4.2 \times 10^{22}$$ atoms, $$2.5 \times 10^{13}$$ free electrons and $$2.5 \times 10^{13}$$ holes. 0.001% of Arsenic doping donatesan extra $$10^{17}$$ free electrons in the same volume. The approximate humberof holes in one $$cm^{3}$$ in the doped semiconductor under equilibrium condition is :
ISRO Scientist or Engineer Electronics 2012
For the following questions answer them individually
Measurementof Hall coefficient enables the determination of :
Siliconis not suitable for fabrication oflight emitting diodes becauseit is :
The band gap of elements arranged in ascendingorderis :
The following statements are made for NMOS & PMOS
1: The carrier mobility in NMOSis higher
2: PMOSrequire less area than NMOS
3: NMOS circuits are smaller than PMOS
4: PMOS are fasterin switching.
Of these, the true statements are -
The following statements are made for FETs
1. In n-channel depletion mode MOSin the active region, the control voltage Veg is negative.
2. NMOSin depletion modeis cut off for $$V_{GS}$$=0
3. NMOSin enhance modeis cut off for $$V_{GS}$$=0
4. There is no path betweensource and drain in the enhancement mode
Of these, the true statementsare :
Special handling precautions should be taken when working with MOS devices. The statement whichis nottrueis :
If the input to the circuit of Figure is a sine wave, then the output will be :
A high gain OpAmp has $$R_{f} = 10^{5} Ω \& R_{f} = 10^{3} Ω$$. The correct statement is:
For various typesofoscillators, the correct statementis:
For Butterworth & Chebyshevfilters, the correct statementis :
In a feedback series regulator circuit, the output voltage is regulated by controlling th
In a fullwave rectifier circuit with centre tap transformer, if voltage between one end of secondary winding and centre tap is 300V peak, then PIV (peak inverse voltage)is
The rms value of the periodic waveform as shown in Figure is
The approximate equivalent resistance between terminals A and B for the following infinite ladder network comprising of 1Ω &2Ω resistors is:
If the step response to the input step amplitude of 1 V is given by $$V_{o}(t)=(1-e^{\frac{-t}{RC}})$$ the network can be represented by:
For a parallel RC circuit as shown in figure, R = 20 QN & C = 0.9 vF, which is to be matched to 50 Q over a bandwidth,
$$\int_{0}^{\infty} \ln \frac{1}{\mid r \mid} dw \leq \frac{\pi}{RC}$$
The circuit has to be matched over 6 GHz to 18 GHz, What is the very best r that can be achieved:
In this circuit, V is a sinusoid input with freq f, current i contains:
The effect of phase error of local oscillator on spectral components in’ coherent detection of SSB Amplitude modulated signal is :
The maximum transmission power efficiency of DSB-C Amplitude modulation is:
For identical total transmitted power, the ratio of $$\frac{S}{N}$$ for wide band FM to $$\frac{S}{N}$$ of DSB-AM (with $$m_a = 1$$)is :
( Given fm = 15 KHz & frequency.deviation =$$\pm$$ 75 KHz)
A signal $$m(t) = 3 \cos(6000 \pi t) + 4 \cos(7000 \pi t) + 5 \cos(10000 \pi t)$$ to be sampled. What is the minimum sampling rate for band pass sampling for truth full representation :
Minimum number of bits required to represent maximum value of given analoguesignal with 0.1% accuracyis:
An Ideal powerlimited communication channel with additive white Gaussian noise is having 4 KHz band width and Signal to Noise ratio of 255. The channel capacityis:
An Ideal power limited communication channel with additive white Gaussian noise with 1 MHz band width and Signal to Noise ratio of 15 is transmitting the | information at theoretical maximum rate. If the Signal to Noise ratio is reduced to 7, how much bandwidthis required to maintain samerate:
Following constellation diagram represents:
The information rate to be transmitted is 900 bits /sec, FEC is $$\frac{3}{4}$$ , the symbol rate for QPSK modulation scheme is:
Electric displacement density D at any point on spherical surface of radius R with a charge Q at the centre ina medium with dielectric constant $$\epsilon$$ is:
Which of the following does not represent Maxwell’s Equation:
For a homogeneous and isotropic medium with a charge density $$\rho$$ & dielectric constant $$\epsilon$$, the Poisson’sequation for electrical potential V is :
For a plane travelling EM wave, the correct equation for characteristic impedance Z for the medium with permittivity of $$\epsilon$$ and permeability of $$ \mu $$ is :
A plane wave propagating in the dielectric medium has an electric field given as $$E_{x} = E_{o} \cos (2.6 \times 10^{10}t -100z)$$. The phase velocity of plane wave is :
A plane wave propagatingin the dielectric medium has an electric field given as $$E_{x} = E_{o} \cos (3 \times 10^{10}t -100z)$$.The dielectric constant of the medium is :
A transmission line of 50 Ω characteristic impedance terminated by a load impedanceof 50-j50. The magnitude of reflection coefficient at the load is :
The outer conductor diameter and the inner conductor diameter dimensions of a coaxial cable are made twice toits original value. (Coaxial line is filled with dielectric material having dielectric constant ¢,= 4.0 ). The correct statementis :
A non dispersive media has:
A plane wave is characterized by $$\overline{E} = (0.5 \hat{x} + \hat{y} e^{\frac{j \pi}{2}}) e^{jwt - jkz}$$ The wave is
if a right hand circularly polarised wave is incident on a perfect conductor. The reflected wave is:
In which of the following cases the divergence of electric field is zero
Skin depth at 2 GHz for a gold conductor with $$\sigma =4.55 \times 10^{7} S/m $$ is 1.5 $$\mu m$$ .Skin depth (in $$\mu m$$) at 8GHZ & 18GHZ is
The S matrix of a lossless line having length $$\frac{\lambda}{4}$$ is
In the following Smith Chart,
the movement from y along a constant VSWR circle to y1 needs addition of
If the RF transmission is terminated in its Characteristic impedance Z,, which of the following statements is wrong :
The loss-less , quarter wavelength long , RF transmission of characteristic impedance 50 Ω_ is terminatedin pureresistive load impedance 100 Ω the input impedanceis:
A lossless matching circuit is shown in the figure
The values satisfying the matching condition are:
The true statement for wave propagation in rectangular wave guidesfilled with air is:
As the wave frequency approachesto cut-off frequency of wave guide, the correct statementis :
The EM wave which does not propagate through a rectangular waveguide with a = 30 mm & b = 15 mm is
The minimum inputsignal that gives outputsignal to noise ratio of 10 dB in a system that has an input impedance equal to 50 Ω, a noisefigure of 4 dB and bandwidth of 100 KHz is :
In this circuit, $$V_{out}$$ is :
The RF amplifier A is having 3 dB NF & 5 dB ofgain, amplifier B is having 3.5 dB NF & 15 dB. For overall noise figure of the cascaded system, the correct statementis :
For this RF Circuit, the correct statement is :
The gain of a parabolic dish antenna of 1 m diameterand 80% efficiency at 9.5 GHzis :
In a uniform linear array, four isotropic radiating elements are spaced $$\frac{\lambda}{4}$$ apart. The progressive phase shift between the elements required for forming -
the main beam at $$60^\circ $$ of the end fireis:
The radiation resistance of a thin line centre fed A/2 antenna with sinusoid currentdistributionis :
To increase gain of a parabolic reflector antenna by 6dBi, the correct
The waveguide Magic Tee can be used as:
The microwave device working on the principal of Faradayrotation is called as:
The phase difference between adjacent anode poles of Magnetron is generally:
Which of the following devices cannot be used as microwaveoscillator:
For a Phase Locked Loop system, the open loop transfer function is G(s)=$$\frac{1000}{s (\frac{s}{1192}+1)}$$
The phase margin is $$50^\circ$$ and the crossover frequency is approximately 1000 rad/s. A time delay is introduced in the phase detector reducing the phase margin to $$40^\circ$$ . The maximum permissible time delay ( in seconds)is :
In this circuit, the relationship between $$V_{i} \& V_{o}$$, is:
Output Impedanceof a source follower is :
For a negative feedback system shown in figure,
the equivalent transfer function is :
If $$(146)_{x}+(313)_{x-2}=(246)_{8}$$, then the value of base x is
The truth table for implementing a boolean variable F is given by
where d represents don’t care states. The minimized expression for F is
The state transition diagram for a sequence generator is shown in figure
It is designed using D F/Fs and combinational logic blocks $$L_{1}, L_{2}, \& L_{3}$$ and is initialized at $$(Q_{2} = 1 ,Q_{1} = 0, Q_{0} = 1)$$
The minimized expressions for O0, O1, & O2 are:
The number of comparators needed in a 8-bit flash type A to D converteris
The register in the 8085A that is used to keep track of the memory address of the next op-code to be run in the program is the :
The Complement Accumulator (CMA) instruction of 8085 processor on execution affects
“Cycle Stealing” in microprocessor parlance refers to
Principle of “locality” is used in context of
If $$A, B \& C$$ are vectors and $$A = 1.u_{x} + 2.u_{y} + 3.u_{z}, B = 1.u_{x} + 1.u_{y} + 1.u_{z}$$ and $$C = 3.u_{x} + 2.u_{y} + 1.u_{z}$$, then $$(A \times B).C$$
The system of equations $$x + y + z = 6, 2x + y + z = 7, x + 2y + z = 8$$ has
$$x = e^{y + e^{y + e^{y + ......}}}$$ then $$\frac{dy}{dx}$$ is
The area bounded by the curve $$Y^{2} = X, Y = X$$ is given by
The eigen values of the matrix are $$\begin{bmatrix}\cos \alpha & \sin \alpha \\ \sin \alpha & \cos \alpha \end{bmatrix}$$
The Laplace Transform of x(t) formed by convolution operator is:
$$x(t) = \left\{t.u(t)\right\}\otimes \left\{\cos 2 \pi t.u(t)\right\}$$
A random variable X has $$\overline{X} = 0 \& \sigma_{x}^{2} = 1$$. Form a new random variable $$Y = 2X + 1$$. The values of $$\overline{Y} \& \sigma_{y}^{2}$$ are:
Person X can solve 80% of the ISRO question paper and Person Y can solve 60%. The probability that at least one of them will solve a problem from the question paper, selectedat random is :
