An SR latch is implemented using TTL gates as shown in the figure
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An SR latch is implemented using TTL gates as shown in the figure. The set and reset pulse inputs are provided using the push-button switches. It is observed that the circuit fails to work as desired. The SR latch can be made functional by changing
A. NOR gates to NAND gates
B. inverters to buffers
C. NOR gates to NAND gates and inverters to buffers
D. 5 V to ground
Please scroll down to see the correct answer and solution guide.
Right Answer is: D
SOLUTION
Concept:
- In the TTL logic gate, open-end or floating end are considered as logic-1.
- For the circuit to work as an S & R latch, S & R should act as logic-0 as well as logic- 1 on requirement.
Analysis:
- If we connect set which is equal to 5 volts, then it will be considered as logic-1.
- If we do not connect 5 Volts to set switch i.e. if we make set switch ‘open’ then it will again be considered as a logic -1, because it is a TTL gate.
- So we have to replace 5 V supply with 0 Volts by connecting it to ground. So logic-0 is also possible for switch ‘set’ & ‘reset’.
Hence for the above circuit to work as an SR latch, 5-volt battery should connect to ground.
Hence option -4 is Correct.