1
GATE ECE 2001
Subjective
+5
-0
For the digital block shown in Figure. 2(a), the output Y=f(S3,S2,S1,S0) where S3 is MSB and S0 is LSB. Y is given in terms of minterms as $$Y\, = \,\sum m\left( {1,5,6,7,11,12,13,15} \right)$$ and its complements $$\overline Y \, = \,\sum m\left( {0,2,3,4,8,9,10,14} \right)$$.  (a) Enter the logical values in the given Karnaugh map [figure2(b)] for the output Y.
(b) Write down the expression for Y in sum-of products from using minimum number of terms.
(c) Draw the circuit for the digital logic boxes using four 2-input NAND gates only for each of the boxes.

2
GATE ECE 2000
Subjective
+5
-0
The operating conditions (ON = 1, OFF = 0) of three pumps (x,y,z) are to be monitored. x = 1 implies that pump X is on. It is required that the indicator (LED) on the panel should glow when a majority of the pumps fail. (a) Enter the logical values in the K-map in the format shown in figure 3(a). Derive the minimal Boolean sum-of-products expression whose output is zero when a majority of the pumps fail.
(b) The above expression is implemented using logic gates, and point P is the output of this circuit, as shown in figure 3(b). P is at 0 V when a majority of the pumps fails and is at 5 V otherwise. Design a circuit to drive the LED using this output. The current through the LED should be 10 mA and the voltage drop across it is 1V. Assume that P can source or sink 10 mA and a 5 V supply is available.

3
GATE ECE 1993
Subjective
+5
-0
The truth table for the output Y in terms of three inputs A, B and C are given in table. Draw a logic circuit realization using only NOR gates. GATE ECE Subjects
Network Theory
Control Systems
Electronic Devices and VLSI
Analog Circuits
Digital Circuits
Microprocessors
Signals and Systems
Communications
Electromagnetics
General Aptitude
Engineering Mathematics
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