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Q. Red (R), Green (G) and Blue (B) Light Emitting Diodes (LEDs) were fabricated using p-n junctions of three different inorganic semiconductors having different band-gaps. The built- in voltages of red, green and blue diodes are VR, VG and VB, respectively. Assume donor and acceptor doping to be ...

Q. Consider a white Gaussian noise process 𝑁(𝑡) with two-sided power spectral density 𝑆𝑁 (𝑓) = 0.5 W/Hz as input to a filter with impulse response 0.5𝑒−𝑡2/2   (where 𝑡 is in seconds) resulting in output 𝑌(𝑡). The power in 𝑌(𝑡) in watts is (A) 0.11                      (B) ...

Q. The circuit shown in the figure is used to provide regulated voltage (5 V) across the 1 kW resistor. Assume that the Zener diode has a constant reverse breakdown voltage for a current range, starting from a minimum required Zener current, IZ min = 2 mA to its maximum allowable current. The ...

Q. A lossy transmission line has resistance per unit length R = 0.05 W/ m. The line is distortionless and has characteristic impedance of 50W . The attenuation constant (in Np/m, correct to three decimal places) of the line is               . Ans: 0.001 Sol:

Q. There are two photolithography systems: one with light source of wavelength λ1 = 156 nm (System 1) and another with light source of wavelength λ2 = 325 nm (System 2). Both photolithography systems are otherwise identical. If the minimum feature sizes that can be realized using System1 and ...

Q. A traffic signal cycles from GREEN to YELLOW, YELLOW to RED and RED to GREEN. In each cycle, GREEN is turned on for 70 seconds, YELLOW is turned on for 5 seconds and the RED is turned on for 75 seconds. This traffic light has to be implemented using a finite state machine (FSM). The only input ...

Q. A p-n step junction diode with a contact potential of 0.65 V has a depletion width of 1μm at equilibrium. The forward voltage (in volts, correct to two decimal places) at which this width reduces to 0.6 μm is  Ans: 0.40 - 0.43

Q. A binary source generates symbols 𝑋 ∈ {−1,1} which are transmitted over a noisy channel. The probability of transmitting 𝑋 = 1 is 0.5. Input to the threshold detector is 𝑅 = 𝑋 + 𝑁. The probability density function 𝑓𝑁(𝑛) of the noise 𝑁 is shown below. If the detection threshold is zero, ...

Q. Consider a binary channel code in which each codeword has a fixed length of 5 bits. The Hamming distance between any pair of distinct codewords in this code is at least 2. The maximum number of codewords such a code can contain is  Ans: 16

Q. Consider the following amplitude modulated signal: 𝑠(𝑡) = cos(2000 𝜋𝑡) + 4 cos(2400 𝜋𝑡) + cos(2800 𝜋𝑡). The ratio (accurate to three decimal places) of the power of the message signal to the power of the carrier signal is   Ans: 0.125