What is Logic circuits: Definition and 18 Discussions

A logic gate is an idealized model of computation or physical electronic device implementing a Boolean function, a logical operation performed on one or more binary inputs that produces a single binary output. Depending on the context, the term may refer to an ideal logic gate, one that has for instance zero rise time and unlimited fan-out, or it may refer to a non-ideal physical device (see Ideal and real op-amps for comparison).
Logic gates are primarily implemented using diodes or transistors acting as electronic switches, but can also be constructed using vacuum tubes, electromagnetic relays (relay logic), fluidic logic, pneumatic logic, optics, molecules, or even mechanical elements. With amplification, logic gates can be cascaded in the same way that Boolean functions can be composed, allowing the construction of a physical model of all of Boolean logic, and therefore, all of the algorithms and mathematics that can be described with Boolean logic.
Logic circuits include such devices as multiplexers, registers, arithmetic logic units (ALUs), and computer memory, all the way up through complete microprocessors, which may contain more than 100 million gates. In modern practice, most gates are made from MOSFETs (metal–oxide–semiconductor field-effect transistors).
Compound logic gates AND-OR-Invert (AOI) and OR-AND-Invert (OAI) are often employed in circuit design because their construction using MOSFETs is simpler and more efficient than the sum of the individual gates.In reversible logic, Toffoli gates are used.

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  1. L

    I Equivalence of these quantum circuits

    In the attached image, there are two quantum circuits that are equivalent. I am trying to understand how. Let's call the top qubit ##q_1## and the bottom one ##q_2##, and the outputs ##q_1'## and ##q_2'##. From what I understand, the C-NOT gate doesn't affect the control qubit. Because Hadamard...
  2. F

    Engineering Combinational Logic Circuits using Logic Gates

    Homework Statement Design a circuit with four inputs and two outputs which realizes the functions : f1 = Σm(0,2,4,5,6,14) f2 = Σm(0,1,4,6,12,14) Homework Equations - The Attempt at a Solution Here's my work : 2 levels (NAND / OR ) 10 gates 17 gate inputs 2 levels ( NAND / OR ) 7 gates 11...
  3. adamaero

    Replacing two corresponding switches as one with AND-gates

    Homework Statement So this is not homework or an assignment, but usually my questions get moved here anyway. This is from a project I'm working on for my job. A user can choose between DPDT functionality (so having "SensorI" be a doorway that goes up and down, reverse) or add another sensor in...
  4. D

    Materials for DTL, TTL circuit analysis

    Hi fellow forum-ers :), I have a test in about two weeks where i am going to be given a dtl or ttl circuit which i have to analyse and calculate its function. The professor said that the circuit given to us will always be a useful and existing one meaning he's going to give us some NAND, NOR or...
  5. Peter Alexander

    How to determine minimum amount of AND and OR gates in PLA?

    Homework Statement Realization of given three functions $$ \begin{array}{c} f_{1}=x_{1}\bar{x}_{2}\bar{x}_{3}+x_{2}x_{3}\bar{x}_{4}\\ f_{2}=\bar{x}_{3}x_{4}+x_{1}\bar{x}_{2}\bar{x}_{3}\\ f_{3}=x_{2}x_{3}\bar{x}_{4}+\bar{x}_{3}x_{4} \end{array} $$ using the PLA. Homework Equations I don't know...
  6. peroAlex

    Designing a 2-bit Comparator with NOR gates

    At our class on digital structures, this assignment has been given. It's a preparation for upcoming lab work, and I'm not sure my design is correct. Is anyone please willing to check it out? 1. The problem statement, all variables, and given/known data Design a two-bit comparator using NOR gates...
  7. AilingLore21

    Having trouble forming an equation on 2 bit subtractor

    Homework Statement We are asked to make a subtractor circuit which has a 2 bit, 2 input data. Homework Equations A1A0 _ B1B0 _________________________________The Attempt at a Solution I would have a 3 bit output with one borrow. The problem is I am stuck at this point and am having...
  8. R

    Engineering Combinational circuit that multiplies two numbers together

    Homework Statement Design a combinational circuit that multiplies two numbers together, and outputs the result. Homework Equations The biggest product will be 3 * 3 = 9. Four bits to represent the product. 0: 00 1: 01 2: 10 3: 11 I need a 4 bit register for the outputs The Attempt at a...
  9. G

    MHB Logic Circuits and Truth Tables

    Hey guys, I'm in a pickle with this question. Its really not my cup of tea, its a struggle factor really but I don't really have a choice whether I like it or not. A worked example such as this allows me to see what it is I need to do. If anyone can provide a helping hand it would assist me...
  10. M

    Timing diagram of flip flop and d-latch

    Tried using the template, had to put pictures because this concerns a diagram question! sorry guys! 1. Homework Statement Consider the circuit shown in the figure below which consists of a positive edge triggered flipflop with selective load capability (identified as MICK) and a level...
  11. T

    Boolean Algebra Question (Digital Logic Circuits)

    Homework Statement The Attempt at a Solution Is my solution correct or can I simplify it even further?
  12. S

    How do logic circuits work?

    I know that if 1 and 0 goes through an OR gate, it gives 1. But how does the 1 come? how it works? thanks
  13. S

    Engineering Logic circuits for boolean functions

    Homework Statement Draw a logic circuit for the boolean function ((p+qr)')(pq+r) do not simplify the function first The Attempt at a Solution I got this: http://screencast.com/t/BC4akgo9J but I'm pretty sure it's wrong because of the first part how the bar goes over the whole...
  14. D

    Engineering Solving Diode Logic Circuits: 4V, B=2V, C=3V

    EDIT: I was being stupid and forgot the first diode would turn off after i worked out stuff for diode C, thanks anyway, solution found!Hi I'm having some trouble getting the correct output voltage when i model the diodes using a voltage ofset and resistors. A = 4V, B = 2V, C = 3V Using Voltage...
  15. P

    Engineering Need a help in making logic circuits

    Homework Statement So I have four bits input(X0,X1,X2,X3), and I need to check if these four bits are monotonic sequence. I got the following function: Y0 = X2X1X0 + X3'X2'X1' + X3'X2'X0 (Y0 - the output 1 when X0>=X1>=X2>=X3) Y1 = X2'X1'X0' + X3X1'X0' + X3X2X1' (Y1 - The output 1...
  16. G

    Engineering Logic circuits with Flip Flops

    Homework Statement A counter has two state outputs y1 (the more significant bit) and y2 (the less significant bit) and a control input x. When x = 0, the states of the counter’s flip-flops do not change. When x = 1, the states of the counter’s flip-flops cycle through the codes of a 2-bit Gray...
  17. V

    Digital logic circuits material

    could anybody suggest me a good learning material for 'digital logic circuits'
  18. K

    Engineering Logic circuits drawing program

    hey I'm really really new to this site and I hope I can get some help. I have a report for the logic circuit lab tomorrow, we need to draw the circuits on the computrer to represent it in the report.. I have no idea about any programs names:grumpy:. so I hope I can get some names for some...