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Questions tagged [logic-gates]

Symbolic representation of ideal devices implementing boolean functions

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boolean algebra question regarding how to simplify a 5 input circuit

Background: I'm teaching myself computer architecture because I do not have a technical degree and want to learn this even though my finances won't ever allow me to have a formal education. I am doing ...
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4answers
628 views

Truth table with logical gates for a traffic light

I want to create this truth table: So I tried this but I was not able to get the last row, which is: While a =1 and b =1 ,yellow = 1 red = 0 and green = 0. This is my design for it, but I could ...
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3answers
73 views

Why is my Gated Latch not a Gated Latch?

After watching the excellent Carrie Anne's Crash Course Computer Science #6 (https://www.youtube.com/watch?v=fpnE6UAfbtU), I tried to design a Gated Latch in Logicly. I played with it a little, and ...
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60 views

Stable states in Flip Flop

I had seen that flip flop have two stable states 1,0 and 0,1 as output. Why are 1, 1 or 0,0 is not a stable state? Or what do you mean by a stable state here?
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Logic behind this automatic gate light

I was doing this circuit which I found on the Internet. My question is what is the logic behind the functioning of this circuit? Thanks!
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54 views

Implementing logic expression and the truth table of logic function

(a) Expression for \$Z\$ \$Z=(B+\overline{C})A+B(C+\overline{D})+BD\$ \$Z=AB+A\overline{C}+BC+B\overline{D}+BD\$ \$Z=AB+\overline{A}C+B\$ \$Z=B+A\overline{C}\$ (b) Truth table ...
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45 views

Can not get the IC version of some gates to show up in KiCad

I don't know if this is a problem with the software i am running, or the way i am trying to go about doing this. But every time i try to place the 74LS04 IC in Eschema it only shows the option to ...
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4answers
73 views

Driving a 74HC series chip with a 74LS series

I made a mistake and accidentally bought a 74LS AND gate: this one. My other chips are 74HCs. I need the output of one of the AND gates to drive the clock signal on a JK flip-flop: this one. ...
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1answer
80 views

Having trouble determining circuit purpose

My apologies if this is the wrong section. I am having trouble trying to determine the purpose of circuit. As in, what would this circuit be useful for, if it was installed in a logic board. The ...
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2answers
62 views

Can CML differential signal lines be flipped to act as a NOT gate?

If I want to invert a CML differential D-Flip Flop (Ex: hmc747lc3c) output before entering into a CML Counter(Ex: MC10EP016), is it as simple as flipping the signal lines before entering the counter? ...
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1answer
65 views

Identifying this logic gate

Could somebody please explain the two logic gates with only the one input, A and B, respectively?? It is a NAND gate, with a box just before it. What is this box? Why only one input?
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Creating coder of MFM linear code (Miller) using logic gates

I have a problem with the implementation of my MFM encoder using logic gates (in the CEDAR program). It's not working correctly, and I don't know if this is software problem, or if I'm doing something ...
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2answers
94 views

MOSFET logic gates: Putting the pieces together

So I got this problem. And I know MOSFETs...Sort of. So the area in red is a NAND gate and the area in blue is an Inverter...I think? So I know what those two pieces are, now how do those connect? ...
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3answers
82 views

7432 behaves like an AND gate & 7408 behaves like an OR gate

Ok. First of all, I'm an absolute beginner about IC and circuits. If you will view the pictures, you will notice that the 7432 behaves like an AND gate and the 7408 behaves like an OR gate. PS. I ...
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41 views

4 bit to 4 bit subtractor logic gates problem

I'm trying to create a 4 bit by 4 bit subtractor here but I get wrong output. In the picture it shows that 0000-1111=10001 which should be 0000-1111=11111. Please help me. By the way the rightmost IC ...
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1answer
48 views

Latching switch to single pulse circuit? (monostable multivibrator with 555?)

I am looking at using a latching switch (SPDT) to momentarily connect two pins. This is for a power button for a raspberry pi, so to power the machine from a hold state you have to momentarily short ...
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1answer
72 views

BCD code Detector

So basically I'm trying to design the circuit for a BCD code detector which should have 4 inputs and gives an output of 1 if the equivalent decimal is 0<=input<=9. Else, it should give zero. ...
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4answers
92 views

TTL Logic for displaying large 7-segment values [closed]

For fun, I was trying to imagine how I might implement large values in 74 series logic (or any commonly available discrete logic from the 1970s). An example might be displaying prime numbers up to ...
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51 views

Building a 6-inputs XOR gate with only 12 AND/OR gates

I would like to compute a 6-input XOR gate with only 12 AND/OR gates, any number of inverters can be used. I failed to find any optimization with the K-map and so far I can only decompose it with 13 ...
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35 views

1-bit maximum selector (iterative design)

I'm trying to create a 1-bit maximum value selector with an iterative design that can solve larger problems. I understand that I go from the most significant bit (MSB) to the least significant (LSB), ...
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2answers
53 views

percision timing ratio of multiple lights blinking with different durations and intervals

I'm learning a lot of this as I go, my background is mostly in programming. I'm trying to setup a timing circuit for two sets of lights going into a model, and am trying to determine the best way to ...
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3answers
48 views

TTL square wave inverter adjustable duty cycle

I am an amateur and I don't have experience with logic circuits so please forgive me if this is very simple. I have a 5V TTL crystal oscillator (4-pin). I need to create a second square wave from it ...
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37 views

Performance issues when using CMOS SR Latch with 180nm transistor models in circuit simulator

I am trying to incorporate a CMOS SR latch made with 180nm Level +49 transistors into a larger circuit but am running into issues. I am hoping this community can point me in the right direction of ...
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5answers
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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 AND ...
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1answer
47 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
36 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 \$...
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1answer
87 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
38 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
44 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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41 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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1answer
56 views

Simplifying logic circuit [closed]

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
70 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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102 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
58 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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68 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
85 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
48 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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92 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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1answer
59 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
81 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
132 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
58 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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45 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
31 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
76 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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88 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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33 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
43 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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68 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 ...