Digital Electronics

Hello everyone, in last blog I told about Communication Systems...

Now before beginning Digital Electronics.. .give 2-4 hrs of time for revision of Communication System ..revise notes,solve questions which you won't able to solve in first attempt..and important topics which you find difficult to understand..so give a quick look to all these and also look for the diagrams ..

Now we will begin our next subject i.e Digital Electronics,,

Study it from :-

• notes(self or coaching)
• Morris Mano
• Salivahan
• few questions from Kannodia
• Previous Year GATE,IES questions

First Read your notes..notes must consist following topics :-

• Defination of basic gates,universal gates and other gates...their implementation w.r.t each other,like converting ex-or gate by using nor gate...also remember how many gates are required.

• Also learn gow to calculate output when delays in gate is given.

• When even no. of not gates are there then it is bistable or flip flop or memory element,if there are odd no. of not gates then it is astable circuit or free running or squrare wave generator or clock oscillator,calculate time delay.

• Implementation of gates using diodes and BJT

• Number System..converting binary to hexadecimal or octal and vice versa.

• Karnaugh Maps,Implicants,Prime Implicants and essential implicants.

• In any equation finding of no. of literals,POS,SOP,relation between minterms,maxterms ..when to write what..i.e if outputs are 0 then write POS or maxterms else write SOP or minterms.

• No. of minterms and maxterms in ex-or gate.

• Complements,addition,subtraction(learn rules from Morris Mano).

• 2's Complement and its rules.

• Logic Families(although it is not in GATE syllabus but required in interviews),advantages and disadvantages.Focus mainly on CMOS,difference between PMOS and NMOS,Transmission gate,DTL,Standard DTL (how replacing diode with BJT helps),HTL(how it reduces noise),TTL(open collector,totem pole,schottky),ECL..Read this from Morris Mano.

• Combinational logic circuits:-half adder,full adder,half subtractor,full subtractor,their implementation by gates and implementation of full adder and subtractor by half adder and subtractor respectively.

• Comparator(for 2 inputs ,3 inputs and so on)..no. of gates required to implement it.

• Multiplexer.demultiplexer,encoder,decoder,priority encoder,no. of multiplexer needed for implementing exor,and ,nor,or and other gates.

• If 2 raised to the power n :1 multiplexer is needed for n input then 2 raised to the power (n-1) :1 multiplexer and on not gate is needed for same input.

• Serial adder,Parallel adder,Look ahead carry adder(no. of and,or gates needed,no. of gates don't depends on input it depends on levels).

• Sequential logic circuits:-Latch,flip flops,characteristic equation,excitation table,difference between latch and flip flop.Asynchronous and Synchronous sequential logic circuits,difference between them.

• Conversion of flip flops into each other.for example S-R to J-K and vice versa and so on..what is D in D-flip flop.

• Flip Flop:- Started from S-R then why J-K came then why master-slave came.

• Difference between level triggered and edge triggered clock.

• Counters:-advantages,Synchronous and Asynchronous difference between them.

• Up-down counter by Synchronous and Asynchronous counter,Error in Asynchronous (removing it by strobe input),Ring counter,Johnson Counter,Series and Parallel Counter,time delay in them..and then find out which is fastest.(take some sequence and try to solve it by synchronous counter for both positive and negative triggered )Learn about preset and clear.Clear by Nand And Or Nor gate according to input and clock.

• ADC and DAC:- Types of ADC and DAC,resolution,error,accuracy,linearity,which is fastest among them.Focus on inverted type DAC and Successive Approximation and Dual Slope type ADC.

• Monostable,Astable and Bistable multivibrator:-Read from Salivahan.

• IC 555 timer.

Note:--Focus on Subtraction,Moore-Mealey finite state machines,Non degenerate forms,Logic families from Morris Mano.

Focus on Master Slave,Astable,Bistable and Monostable multivibrator from Salivahan.

Digital electronics is easy subject try to learn every topic and focus on previous year questions as much possible.

Do previous year GATE,IES questions and questions from Kannodia.

Best of Luck ..prepare well..if have any doubt then do comment..

Next Subject we are going to take is Microprocessor..

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