Electrical Engineering Stack Exchange
Electrical Engineering Stack Exchange

Questions tagged [digital-logic]

Digital electronics treats discrete signals, unlike analog electronics which treats continuous signals. Digital logic is used to perform arithmetic operations with electric signals and constitutes the base for building CPUs.

Digital logic deals with the design of hardware that processes only two values, which are usually denoted as 0 and 1. These two values represent a binary number system.

For more information, see the Wikipedia article.

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How is an XOR with more than 2 inputs supposed to work?

I've just started studying computer engineering, and I'm having some doubts regarding the behavior of the XOR gate. I've been projecting circuits with Logisim, whose XORs behave differently from what I've learnt. To me, it should behave as a parity…
gabrieljcs
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Why are NAND Gates cheap?

In my digital electronics labs and lectures we are told to try and make things from NAND gates, because they are the cheapest kind of gate available to buy. Why is this? Why isn't an OR/AND gate the cheapest to buy?
Dean
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74HC/HCT: What to do with unused inputs and why?

If I'm using an IC in the 74HC or 74HCT family, and I'm not using all the input pins, I understand that I should not leave them unconnected because they will float. But what exactly should I do with them, and what are the pros and cons of the…
jnrbsn
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Why do we add 6 in BCD addition?

Sometimes, if the sum of two digits are < 10, BCD addition is similar to binary addition. But sometimes if the sum > 9, the result requires a correction. This corrections is +( 0110). Why do we add 6? Why not some other number? I searched the web,…
mine wwe
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What type of Boolean logic circuit is this?

I need help confirming some hunches. I'm trying to figure out what type of circuit this is: Any ideas? Also, I think the logic expression for this is: D = (A AND B) OR (NOT(B) AND C)
Chattanoogan
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How to convert an expression from SOP to POS and back in Boolean Algebra?

How to convert a Sum of Products (SOP) expression to Product of Sums (POS) form and vice versa in Boolean Algebra? e.g.: F = xy' + yz'
user2912
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Is there a logic gate which directly outputs (A'B)' (complement of, A complement product B)?

I know I can do this with two separate NAND gates, but it would be more space consuming. Is there a single standard logic gate (e.g.; 74V1Gxxx - SOT-23 package is preferred) which produces this result? Or, can I get this result by using two…
hkBattousai
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What is a three-state circuit?

I have read the Wikipedia article Three-state logic, but it is not clear enough. What is a more simple explanation for what a three-state circuit is? When and where do we use it? What has CMOS to do with three-state circuits?
Despre Femei
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How is unsigned integer max implemented in hardware?

I'm working on a design that involves a lot of max functions (and max functions as arguments to other max functions). In an effort to simplify the hardware design I was wondering how max is implemented in hardware? Mathematically, Max(a,b) can be…
James
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Why should you not leave the inputs of unused gates floating with 74LS series logic?

I have seen much info explaining that the inputs of unused gates in a multi-gate IC (say, 74LS00, which is a quad-gate, where only 3 gates are used) should not be left floating, but I cannot find any technical reason as to why this is the case. The…
CoolBots
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74S vs 74LS ICs UND EE201L

I am starting my EE degree. I must purchase a myDAQ and a kit. The kit lists many logic ICs and I have most of them, but some of what I have are 74S instead of 74LS series. Will the extra power draw on the 74S ICs cause issues with the myDAQ? …
Psubond
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Get number of set bits in digital logic

As an exercise, I am trying to design an implementation of Conway's Game of Life in simple digital logic. I could do the whole thing by minimizing a 9-Variable function, but I imagine that will still be fairly large. One of the core elements of the…
captncraig
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what is a bus (physically) in digital design?

Is bus a bunch of wires connected between functional blocks? or does it have any other functional importance? if possible, someone please provide some material to get some clear understanding.
Raviteja
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How to build an interesting XOR circuit with my child's electronics kit

When I got home today, my child was proudly telling me how they had managed to make AND, OR, and NOT logic from his snap circuits electronic kit and was asking me how they could make exclusive or. Has anyone any suggestions for a simple (and…
Peter de Rivaz
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AND gate design using MOSFETs

About designing AND gate using N-type mosfets: first image is used everywhere. However, it uses an additional inverter part. Is it not possible to design the circuit like below (second image)? If not, what is the reason for that?
mert
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