Questions tagged [logic-gates]
Symbolic representation of ideal devices implementing boolean functions
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Why does a single AND gate need 60 transistors?
Looking at the datasheet for the MC74VHC1G08, under the "features" section, it states Chip Complexity: FETs = 62.
Why does this IC need 62 transistors, while an ...
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1answer
38 views
Circuit MOSFET Pulldown Circuitry
Now, I have already made some progress, I have figured out what the W/L should be and made most of the circuit. Though I am not sure how I should put the MOSFETs ...
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1answer
33 views
Signal Period of each stage in a ring oscillator
Considering the following ring oscillator:
I know that the Frequency at \$Q\$ is given by
$$f=\frac{1}{2*t_{PD}*3}$$
Yet I want to calculate the period of each signal at \$V_{1}\$,\$V_{2}\$, and \$...
2
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1answer
82 views
Logic circuit designs in industry
i wanted to ask what logic designs are used in industry for different logic functionalities?
So for example XOR gate:
The 1st image would probably save more space on a circuit, but for the second ...
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1answer
29 views
Noise immunity and noise margin
Why is noise margin in logic gates a quantitative measure of noise immunity?
Can anyone provide an instantiation to demonstrate how noise margin is a measure of noise immunity
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2answers
42 views
Chaining pull-up vs push-pull configuration
The first image is the push-pull configuration.
Current is drained to GND through the PMOS and NMOS
The second image is the pull-up configuration
Current is drained to GND through the large resistor
...
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29 views
Time to register transition between 1's and 0's AND gate [on hold]
How to calculate the time between the transition registered output 1 to registered output 0 and vice versa?
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18 views
Converting 4 4 3 -2 Weighted Code to BCD using Decoder
I've been trying to solve a question - Design a 4 4 3 -2 to BCD converter using decoder.
My attempt at the question was to make the truth table for the 443-2 code and then write the binary ...
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0answers
38 views
Simplifying logic circuit
I've been trying to simplify a combinational circuit and wanted to know whether there was any simpler way of solving such questions. Do we have to find all the outputs and such or we can use a simpler ...
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1answer
56 views
HC vs LVC for 3.3V Logic
I am designing a circuit in which Vdd=3.3V. I have checked datasheets of hex inverters 74HC04 and 74LVC04 and both of these can work good at 3.3V logic circuits. If I have to select one of them then ...
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1answer
25 views
Converting full adder to subtractor using inverter
I've been trying to convert a full adder to a full subtractor using an inverter.
I tried using not gates at the B input ( in A B Cin ) and also using it in the outputs but the final answers are not ...
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2answers
51 views
Power consumption open collector/drain
https://www.allaboutcircuits.com/technical-articles/the-i2c-bus-hardware-implementation-details/
I read from this article that for the open drain there's nontrivial power consumption when the input ...
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66 views
Pull up and down resistors
Since inputs to logic gates a susceptible to noise which could cause a voltage on the inputs
Are pull up and pull down resistors always used in logic gates?
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39 views
Logic Style Level Vs Hardware Level
In the book: Advanced DPA Theory and Practice: Towards the Security Limits of Secure Embedded Circuits 1, it is explained that the countermeasures against Side-channel Cryptanalysis could be ensured ...
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1answer
38 views
Minimum number of NAND gates to implement f(x,y,z,w)=x(y+zw)+yz'
As the title states, given a function f(x,y,z,w)=x(y+zw)+yz', what are the minimum number of NAND gates you need to implement f?
My first attempt at a solution was to draw a kmap to see if there was ...
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1answer
39 views
Logic gates with Mosfets and Transistors
Does anyone have a link for the list of all the configurations of BJT and MOSFET which create the logic gates?
Like for NAND gate below:
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28 views
Designing Excess 5 to BCD using Binary parallel adder
I've been trying to form a combinational logic circuit of converting excess 5 to BCD. I've been able to make a normal logic circuit but I do not know what a binary parallel adder is.
My attempt - ...
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0answers
40 views
Components Naming [closed]
I was wondering what is the rule behind naming the components, and why there are names/numbers that are close to others while having really different functions.
For instance, in logic circuits, the ...
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1answer
54 views
How to differentiate 01 and 10 in logic gates?
I'm looking for a device with the following truce table:
The 00 and 11 case can be done with NOR and AND, but XOR can not tell 01 and 10 apart.
So my questions is: Is there a device with such truce ...
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1answer
78 views
How to design an AND gate for 24V AC Thermostat Connection
I have a two stage furnace with a heat pump, and a thermostat that isn't capable of controlling the second stage of the furnace when in heat pump mode.
However, I can configure it in such a way that ...
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1answer
106 views
What is this question trying to ask?
I'm not an electronics students, I was doing erasmus for my chance I got electronics education, I have a project to complete I've made 9 of 10 exercises but I'm unable to understand what this question ...
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1answer
54 views
voltage drop - operating a solenoid after a logic gate and a LED
I have started meddling in circuitry, but I lack any sort of formal training.
Subsequently I apologise for my ignorance.
The circuit I have made (on paper) so far has a number of issues, but I want to ...
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0answers
44 views
Binary multiplyer by 8
How can I design a circuit that take 3 inputs lines and multiplies these inputs by 8 using only 4 bit full adder ?
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1answer
29 views
NAND Simplified with xy + !x z
I've been trying to work on a few problems, though I'm not sure how to rewrite this a few circuits using only NAND/NOR -->
an example is shown below;
How am I able to rewrite only using NAND + NOR ...
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1answer
72 views
What is the name of this logic circuit?
Sorry for dumb question, I'm really newbie in electronic.
As I wrote in topic, What's the name of this circuit? Dose the circuit has any specific name at all ?
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2answers
81 views
Better Transistor Inverter Using Ground Signal?
I'm getting close to finishing my brand spanking new gate control design. I sincerely appreciate all the help I've received out here.
My latest challenge is to extinguish an LED when a circuit is ...
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0answers
30 views
Dimensioning a “NOT” gate with a bipolar NPN transistor
With the schematic below I am to determine a "NOT" gate the value of Rb to which the circuit acts as such, knowing that the voltages given for the logic levels are:
$$0\to V\in[-0.3,0.9]$$
$$1\to V\in[...
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2answers
40 views
Logic Circuit Transistor Resistor Values?
Last week, I posted a problem with a logic circuit (Need Help With Transistor Logic Circuit Design), and Analogkid was kind enough to solve it. However, at the time, I didn't realize I still had a ...
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0answers
44 views
How to logically solve logic gates
Reading the Digital Multiplexers article on Wikipedia following is written:
A 2-to-1 multiplexer has a boolean equation where A and B are the two inputs, S is the selector input, and Z is the ...
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4answers
113 views
Need Help With Transistor Logic Circuit Design
Greetings all and Happy New Year!
I've been working on a logic circuit to control the main entrance gate at our ranch for some time now. I've been testing using Falstad's Circuit Simulator.
...
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3answers
106 views
How to build logic gates?
I'm thinking of ideas for a school project and one of the better ones was to build a calculator from scratch using only wire and basic electrical components. I've seen very many marble, Lego, domino, ...
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1answer
21 views
SNM (Static Noise Margin) and DNM (Dynamic Noise Margin) confusion in digital circuits
I've found in several sites that SNM is the min between NMH and NML where NMH=VOHmin-VIHmin and NML=VILmax -VOLmax
But this paper really confuses me, because it uses the same graphics and apparently ...
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1answer
81 views
Logic Design simple door security system with using MUX
I draw the cicuit without using any MUX. But my project says I need to use 4x1 MUXs
and I couldn't find where to use 4x1 MUXs. I tried put MUX of each output but this was very pointless, no need to ...
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5answers
182 views
Boolean circuit - 4 bits divisible by 3
I need to draw a circuit taking a number on 4 bits that will return 1 only if that number is divisible by 3.
My initial steps were to draw a truth table from which I got a Boolean expression that ...
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0answers
38 views
how to show a bunch of numbers one by one on a seven segment display
The question is on the title. I just need a starting point like should I draw first the state diagram? I need to show the 150707926 on one seven segment display one by one by using logic gates. Thanks ...
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1answer
157 views
How can I make the design simpler?
I have designed a circuit and it is working. However, I think it is too complicated and can be changed or simplified. I might be missing something. I am finding hard to create a 1 second delay.
A ...
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2answers
43 views
Converting expression to only use NAND gates
How would I go about converting this Boolean expression so that it would only use NAND gates in its circuit?
A ⋅ ¬B ⋅ ¬D + ¬A ⋅ B ⋅ ¬C ⋅ D
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2answers
33 views
Multiplexer diagram of \$C = A \cdot B\$
I'm having some trouble figuring out how to illustrate, as a diagram, a multiplexer. I realise that a multiplexer takes in a number of input signals and depending on the control sign, outputs the ...
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2answers
56 views
What do the product and sum symbols mean in digital systems?
I have some questions in a professor's material and in that questions there are the mathematical symbols for product and sum receiving numbers as parameters as following:
∑(0,3,4,6) =∏(1,2,5,7).
...
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1answer
66 views
There's Conflicts in the Definitions of XNOR? [duplicate]
XNOR has two definitions:
\$1^{st}:XNOR=NOT(XOR)\$
\$2^{nd}: XNOR(A,B)=\overline{A}\cdot\overline{B}+A\cdot B\$
The problem is that these definitions are not equal in Odd inputs, the second ...
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3answers
79 views
Why does a full adder need an OR gate?
I have read and I understand how the full adder works (or atleast I think I do :D). It combines two half adders and either one of them can have a carry over, hence the OR gate. But why do we need ...
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2answers
73 views
How do logic chips (74LS, HC, …) provide output=Vcc/0V when all standalone diodes and transistors suffer voltage drops?
If you use a transistor to pull signal to high from a Vcc of 5V, signal only goes to 4.5V or so because of voltage drop over the transistor.
Likewise if you use a transistor to pull signal to ground, ...
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1answer
59 views
Diodes needed (parts) for OR gate automotive relay circuit
I need to power up a make-or-break simple automotive relay (4pin, 40A 12V) via an OR gate.
OR gate as follows:
Source 1 is the cable that provides +12V to activate car dome light which I will tap ...
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1answer
29 views
Digital Circuits (GATE)
For two input AND gate what will be the output if one input is 3.3v and other input is 5v?
Ref: VCC=5v, GND=0v.
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1answer
39 views
Rise time different from fall time; relationship differs between AND and XOR gates
I'm looking over the results from a lab I did in an introductory electronics class, and found something I'm unable to explain.
We measured the rise and fall times for two logic gates in this absolute ...
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1answer
100 views
How do I make a double dabble circuit with logic gates
Im attempting to make a 8 bit binary calculator that displays on multiple seven segment displays. Can double dabble be done with logic gates. If so, how?
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2k views
AND Gate Stays Open
I have a very simple circuit on a breadboard with two push-button switches, an AND gate (74LS08), and an LED. I have the two switches hooked up to pins 1 and 2, while the LED goes from 3 to ground. ...
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1answer
69 views
Make a circuit that indicates an odd number of ones using a 3-8 Demux and two logic gates
Using 3-8 Demux and two logic gates, make a circuit that received 4 bits and returns 1 if the number of 1's is odd and else returns 0.
My try:
Using truth table, we get that the desired function is:
...
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1answer
96 views
How can I convert binary into multiple 7 segment displays [closed]
I've been trying to make a decimal calculator using binary adders that feed into 3 x 7 segment displays. I cant find an efficient way to do this. If someone could point me to the correct resources, or ...
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2answers
64 views
How to get the MSB into a logic gate which will check if a number is negative or not?
I need to create a logic gate which will find out whether a number is negative or not.
The input is 8 bits and the output is 1 bit, and if the input is 1 (i.e. negative number) then the output ...
