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1.
Statement for Linked Answer Questions :
Two products are sold from a vending machine, which has two push buttons P1 and P2. When a button is pressed, the price of the corresponding product is displayed in a 7-segment display.
If no buttons are pressed, ‘0’ is displayed, signifying ‘Rs. 0’.
If only P1 is pressed, ‘2’ is displayed, signifying ‘Rs. 2’.
If only P2 is pressed, ‘5’ is displayed, signifying ‘Rs. 5’.
If both P1 and P2 are pressed, ‘E’ is displayed, signifying ‘Error’.
The names of the segments in the 7-segment display, and the glow of the display for ‘0’, ‘2’, ‘5’ and ‘E’, are shown below
Consider
(i) push button pressed/not pressed is equivalent to logic 1/0 respectively
(ii) a segment glowing / not glowing in the display is equivalent to logic 1/0 respectively.
[1] If segments a to g are considered as functions of P1 and P2, then which of the following is correct? [2 marks]
(A) g = P1 + P2, d= c+e
(B) g = P1 + P2, d= c+e
(C) g = P1 + P2, e= b+c
(D) g = P1 + P2, e= b+c[2] What are the minimum numbers of NOT gates and 2-input OR gates required to design the logic of the driver for this 7-segment display?
[2 marks ]
(A) 3 NOT and 4 OR
(B) 2 NOT and 4 OR
(C) 1 NOT and 3 OR
(D) 2 NOT and 3 ORasked in Electronics and Communication Engineering, 2009
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2.
Statement for Linked Answer Question ::
Consider the CMOS circuit shown, where the gate voltage VG of the n-MOSFET is increased from zero, while the gate voltage of the p-MOSFET is kept constant at 3 V. Assume that, for both transistors, the magnitude of the threshold voltage is 1 V and the product of the transconductance parameter and the (W/L) ratio, i.e. the quantity µCox (W/L), is 1mAV-2.
[1] For small increase in VG beyond 1V, which of the following gives the correct description of the region of operation of each MOSFET? [2 marks]
(A) Both the MOSFETs are in saturation region
(B) Both the MOSFETs are in triode region
(C) n-MOSFET is in triode and p-MOSFET is in saturation region
(D) n-MOSFET is in saturation and p-MOSFET is in triode region[2] Estimate the output voltage Vo for VG= 1.5V [Hint: Use the appropriate current-voltage equation for each MOSFET, based on the answer to above question]. [2 marks]
(A) 4- 1/√2 V
(B) 4+ 1/√2 V
(C) -√3/2 V
(D) 4+ √3/2 Vasked in Electronics and Communication Engineering, 2009
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3.
The amplitude of a random signal is uniformly distributed between -5V and 5V.
[1] If the signal to quantization noise ratio required in uniformly quantizing the signal is 43.5dB, the step size of the quantization is approximately
[2 marks]
(A) 0.0333V
(B) 0.05V
(C) 0.0667V
(D) 0.10V[2] If the positive values of the signal are uniformly quantized with a step size of 0.05V, and the negative values are uniformly quantized with a step size of 0.1V, the resulting signal to quantization noise ratio is approximately
[2 marks]
(A) 46dB
(B) 43.8dB
(C) 42dB
(D) 40dBasked in Electronics and Communication Engineering, 2009
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4.
The Nyquist plot of a stable transfer function G(s) is shown in the figure. We are interested in the stability of the closed loop system in the feedback configuration shown.
[1] Which of the following statements is true? [2 marks]
(A) G(s) is an all-pass filter
(B) G(s) has a zero in the right-half plane
(C) G(s) is the impedance of a passive network
(D) G(s) is marginally stable[2] The gain and margins of G(s) for closed loop stability are [2 marks]
(A) 6dB and 180º
(B) 3dB and 180º
(C) 6dB and 90º
(D) 3dB and 90ºasked in Electronics and Communication Engineering, 2009
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5.
Consider a silicon p-n junction at room temperature having the following parameters:
Doping on the n-side = 1x1017cm-3
Depletion width on the-side = 0.1µm
Depletion width on the p-side =1.0μm
Intrinsic carrier concentration = 1.4x1010 cm-3
Thermal voltage = 26mV
Permittivity of free space = 8.85x10-14 F.cm-1
Dielectric constant of silicon = 12
[1] The built-in potential of the junction [2 marks]
(A) is 0.70V
(B) is 0.76V
(C) is 0.82V
(D) cannot be estimated from the data given[2] The peak electric field in the device is [2 marks]
(A) 0.15 MV.cm-1 , directed from p-region to n-region
(B) 0.15 MV.cm-1 , directed from n-region to p-region
(C) 1.80 MV.cm-1 , directed from p-region to n-region
(D) 1.80 MV.cm-1 , directed from n-region to p-regionasked in Electronics and Communication Engineering, 2009
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