Logic Families Interview Question Answer - 4

Important Questions of Logic Families

In this post, some of the important questions of logic families are given. It includes application of ECL, wired ORed, fan out of the ECL, unit of noise margin, differential input ECL, MOS logic, advantages and disadvantages of MOS logic family, MOS logic, features of the ECL, propagation delay of the MOS logic, LSI, VLSI and ULSI application, Application of MOS logic and Speed of MOS Logic.

Write the application of the ECL.     

Application of ECL

• Super-fast computer
• High speed applications

Why the ECL gates can be wired ORed?  

• When the ECL is wired ORed, the noise spikes are not generated and complementary output is possible.

Give reason ‘The fan out of the ECL is large’.  

• The fan out of the ECL is large due to low output impedance.

Why the inverters do not require in the ECL?  

• The ECL do not requires inverters because it produces the output and its complement.

Write three features of the ECL.       

Features of the ECL

• High speed
• Less noise margin
• Large fan out
• Spikes are not generated

What is unit of noise margin?  

• The noise margin is represented in milli voltage.

Describe the advantage of the differential input ECL.        

• The advantage of the differential input ECL is that it provides common mode rejection.

Which logic family requires level translator?    

• ECL

What is reason behind the name ‘MOS logic’? 

• Because it uses metal oxide field effect transistor in the logic circuit.

Describe the advantages and disadvantages of MOS logic family over Bipolar logic family.     

Advantages

• Simple
• Easy to fabricate
• Less power requires
• Better noise margin
• High fan out
• Wide range of supply voltages
• It requires less chip area

Disadvantages

• It may be damage due to static charge.
• Slow operating speed
• Large propagation delay

Why the propagation delay of the MOS logic is very large?       

• The propagation delay of the MOS logic is very large due to capacitive loading by driven gates and high output resistance.

Why the MOS logic is simplest to fabricate?

               OR

Why the MOS logic is used for LSI, VLSI and ULSI application?

• The MOS logic is used for LSI, VLSI and ULSI application because of
• Simplest to fabricate
• It occupies less space.
• It requires only one element i.e. NMOS or PMOS transistor
• Low power dissipation per gate

Why the MOS logic is not used for SSI and MSI application?   

Speed of MOS Logic

• The operating speed of the MOS is slower than that of the TTL therefore the MOS logic is not used for SSI and MSI applications.

State the application of the MOS logic.     

Application of MOS logic

• Calculator chips
• Large microprocessor
• Large memories

Give reason: The MOS logic may be damaged by static charges.

• The MOS logic may be damaged by static charge due to high impedance of the MOSFET’s input.

 

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