logic gate’s

combination of logic circuits it is type of digital LOGIC CIRCUIT which is implemented by boolean circuits where the output is are function of the present input output.

characteristics of combinational circuits.

  • the output of combinational circuits at any instant of time depends on present input only.
  • the previous state of input state does not have any effect on the present state of the circuits.
  • circuits have n numbers of inputs and m number of out puts.
  • they do noty have memory element.


  • adders
  • substractors
  • encoders
  • decoders
  • comaparaters
  • multuiplexer
  • demultiplexer.


a full of adders cktb can be used as part of many other larger ckt like -ripple carry adder.used to perform, carry out multiplications adders are usd in airthmetic logical unit used other parts of processors in calculating of adders table indices &and similar others operations.

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the half adder cicuit adds two binary digits and proceduses a sum and carry output concider a product term for each case where the sum is s 1 in the truth table .there are two such cases. now consider the product term for each case where he carry is 1 in the truth table .


the full adder afds the bits a&b and the carry from the previous coloumn.it generates a sum and carry output.


  • half substractor is an airthmetic circuit that substracts on bit from another bit proceding a defference bit & borrow bit.
  • the difference is a 1 only if the input variable are not equal.it equal one or gate . for borrow require one not state & gate .

full substractor is an airhhematic is an airthmaetic circuit that substance ane bit of from another abit taking into consideration.

the borrow from the lowed taking into considerance the below from the lower coloumn . it proceduds a different & borrow. cosider a product from for each case where borrow is the 1 in the truth table.
used for alu in computer to substract as cpu .
in appliactions of graphics to decease the circvuite difficailtuy
to perform airthmetic function in electric calculations in digital devices.
an encider has numer of input lines only one of which bit activate in given time.
it produces an m bit output code depending on which input is activated.
this is some short information about Adders, Substractor, encoder Remaining there Logic gates Explanations available in next blog.

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