search
Log In
0 votes
316 views
$Exclusive-OR$ gate has a propagation delay of $10$ ns and that the $AND$ or $OR$ gates have a propagation delay of $5$ ns.What is the total propagation delay time in the four-bit adder.Assume $FAN-IN =2$

$1)$ ripple adder

$2)$ carry look ahead adder
in Digital Logic
edited by
316 views
0
Kindly mention the FAN IN of the logical gates to be used.

1 Answer

0 votes

1. Ripple carry adder
Tcarry= 4*(5+5)=40
Tsum=(4-1)*(5+5)+2*10=50
Total propagation delay=40+50=90 ns

Carry look ahead adder

TSUM = Pi+Ci

.              = Exor+ and+or+exor gate  time

.              = 10+5+5+10=30 ns

 


edited by
2
I guess answer is 80 for RCA.
0
Can u plzz elaborate little bit
0

@iarnav getting same 80 for rca

0
I think 3*20 + 20 =  80 for RCA

Related questions

4 votes
3 answers
1
2.7k views asked Nov 14, 2015 in Digital Logic Anil Khatri 2.7k views
2 votes
1 answer
2
399 views
Which of the following statements is/are true? S1: Carry look ahead adder is faster compared to a ripple carry adder. S2: The cost is higher for a carry look ahead adder compared to a ripple carry adder. S1 only S2 only Both None of these
asked Jul 16, 2016 in Digital Logic sh!va 399 views
0 votes
2 answers
3
668 views
Count the 2 Input And, OR and EX-OR gates required in Carry Generator and Look ahead adder. Note :- In the question it is asking about 2 input, not multiple input, for Multiple input AND gates in n bit carry generator we require (n(n+1))/2 and OR Gates n.
asked Sep 30, 2017 in Digital Logic Shubhanshu 668 views
2 votes
0 answers
4
256 views
In a $4-$bit carry look ahead adder, the propagation delay of EX-OR gate is $20ns,$ AND and OR gates is $10ns.$ The sum and carry output of full adder takes $20ns$ and $10ns$ respectively. The total propagation delay of the above adder in $ns$ is
asked Oct 5, 2016 in Digital Logic Hradesh patel 256 views
...