Questions tagged [logic-gates]
Symbolic representation of ideal devices implementing boolean functions
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2answers
33 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
30 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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0answers
39 views
Explain in detail how this configuration can realize the NOT logic operation between those two inputs [on hold]
Assume that input V1 and V2 inputs can take high (5V) and low voltages (0V). Sorry if my circuit may not be entirely correct. I am a new contributor and only just started to learn how to use ...
0
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2answers
51 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
63 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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votes
3answers
71 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 ...
0
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2answers
69 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
37 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 car dome light which I will tap into and
source 2 is engine-on port ...
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0answers
33 views
Simplifiying a boolean expression with only XOR gates
I have a boolean expression which I simplified with a K-MAP. I just want to implement it with only XOR gates, I tried many ways but couldn't manage it. Is that possible to turn this expression into "...
0
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1answer
26 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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0answers
38 views
4bit multiplier combination circuit logisim [duplicate]
The question asked for multiplier 4-bit systems
I'm new in this topic so i don know is this correct or not....
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1answer
34 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
66 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?
7
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4answers
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. ...
1
vote
1answer
45 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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votes
1answer
48 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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0answers
26 views
How do I draw a gate diagram using minimal number of NOR gates for a 7 segment display that outputs CHOP?
My teacher has given us the chance to pull up our grade with this take home question. However he did not cover this in class and I cannot find any good material to solve. Any help would be appreciated!...
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2answers
47 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 ...
0
votes
1answer
72 views
How to find out if the input of a logic gate is negative in two's complement?
I'm trying to create something which will output whether the input of the logic gate is a negative number or not in two's complement. I understand how twos complement works etc, but i'm not entirely ...
0
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3answers
57 views
How to find out if a binary number is zero or not using logic gates?
I'm trying to put some logic gates together which would perform a task of finding out whether a number is zero or not. I came across a thread like this on here already (How to find out if a binary ...
0
votes
1answer
75 views
How do we decide which circuit is a latch?
Will A and B always be the complement of one another regardless of
what logic gates we use in the latch-like circuit? For instance (the
two circuits shown as examples):
How do we decide whether A and ...
0
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1answer
18 views
Help with demonstrating the meaning of this information
Regarding the following information about open drain and push pull configurations:
The advantage of the push-pull output is the higher speed, because the
line is driven both ways. With the pull ...
0
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2answers
48 views
Question on output of an FPGA
I have been trying to solve this basic FPGA problem with multiplexers, but I cannot garner the meaning of the notation 0/1. Can someone throw some light in this regard? What do notations like 0/1 mean?...
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1answer
35 views
Analog logic circuit with adjustable threshold
I have a logic circuit currently consisting a few few AND gates and it's working fine (simulating) with if i use logic levels as the inputs. However my input levels might change in amplitude and I'd ...
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0answers
44 views
signed adder and subtractor
I need to create a circuit that accepts 2 numbers that consist of 4 bits (the first bit is their sign and the 3 rest the number).then with an input S I will choose whether i want to subtract them or ...
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votes
1answer
42 views
Not gate that differentiates between 0V and GND
A not gate typically just inverts the signal, so that V would turn into GND, and GND into V. Is there a not gate using transistors that would switch GND into V, but not switch 0V into V? (preferably ...
0
votes
1answer
64 views
Diode OR circuit drive current
Why is there no drive current available from the circuit below when R is connected to 0V?
The last sentance in this extract from wikipedia states that
If R is connected to 0 volts it will have no ...
0
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0answers
57 views
Logic-based light system
I need to develop a system that turns on the red light when all three switches are off, and turns on the orange light when any two out of three switches are off. The red light part is already sorted ...
0
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3answers
34 views
Low voltage form a NAND logic gate then the state is high
I've been trying to learn how to use logic gates. I wanted to use logic gate to bump digital signal from 3.3V MCU to a 5V. I took a T74LS38D1 and mocked the solution using two switches connected to 3....
0
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1answer
59 views
Pull-down resistors on logic gate and decoder inputs?
I'm designing a very basic circuit for testing a switch sequence. I'm using a CMOS decoder CD4028B (link to datasheet) and XOR gate (CD74HC86E - link to datasheet). Reading the switch sequence is ...
0
votes
1answer
62 views
Reimplement circuit using 1 2x4 decoder and 2 logic gates
I am a Computer Science undergraduate taking a module on Computer Organisation. There is this typical circuit design question that always appear in my assignment and I'm not sure what is the standard ...
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1answer
58 views
XOR complement simplification
What is (A⊕B)' simplification?
i know that :
> (A⊕B)=A'B+AB'
but what is the complement of that expression?
2
votes
2answers
178 views
Implementing a function using decoder, encoder and some gates
Implement the function F(A,B,C,D,E) = A’B’C’DE’+ABCD’E using only the components required from the ones given below:
One 3:8 decoder with active high outputs and an active high enable input
One 8:3 ...
0
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4answers
199 views
Replacing a diode-OR gate by a circuit that behaves the same way (also in the presence of feedback loops) without accumulating voltage loss
Consider the following circuit with two OR gates:
simulate this circuit – Schematic created using CircuitLab
and the Time Simulation:
The OR gates with both inputs 0 generate 0, and after ...
1
vote
0answers
197 views
Is it possible to build memoryless logic gates? [duplicate]
I would like to build a memoryless (possibly cyclic) logic circuit.
Perhaps this is not the best name, so let me illustrate what I would like to have with an example.
Consider a state machine with ...
1
vote
2answers
1k views
Circuit to Breadboard [duplicate]
I'm currently working on a project which requires me to test the functionality of TTL logic gates by making use of diodes and resistors. To do so I must first place them on the breadboard and then ...
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1answer
36 views
Understanding connection of inputs and outputs of digital circuits - voltage and currents requirements
I looked for resources to find solutions to these kinds of problems online, but I couldn't find them. Please, feel free to recommend resources to study from. This is a homework question. I can't find ...
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1answer
136 views
H-bridge MOSFET NAND gate driver suffered from logic voltage drop
I've tried to reproduce the NAND Schmitt triggers circuit to drive my H-bridge MOSFET as per following source:
http://axotron.se/index_en.php?page=34&chapter=0
All my design files are at this ...
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2answers
73 views
how to control power within a triangle automatically
I have two mains powered extract fans with sensor operated controllers.
I need to add a third extract fan that will run if either or both of the other two are on.
How do I wire this so to prevent ...
0
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2answers
56 views
Converting this logic condition possible without programming?
I've been busy trying to make a relay print which has 8 inputs of around 6V-24V that powers the relay. However, I want to add a dipswitch which is able reverse the input-relay relation behavior. ...
0
votes
2answers
41 views
Indicator light for circuit powered off
The background is
Off road motorcycle Radiator fan, temp controlled circuit is powered when key on power is present.
User wants a manual switch to kill the circuit...thats easy enough.
A Power on ...
2
votes
2answers
130 views
Prevent NPN Transistor Base-Emitter Current
I'm making a simple AND gate array out of 2n2222 transistors. Here is one cell:
simulate this circuit – Schematic created using CircuitLab
When Input "A", is disabled, and "B" is still on:
...
40
votes
8answers
8k views
Why are NAND gates used to make AND gates in computers?
Why is this a standard for AND gates
when it could be made with two FETs and a resistor instead?
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vote
0answers
49 views
Jellybean Radio Button logic Chip
Below is an LTSpice simulation of a 'radio button' circuilt.
Ignore the bottom button, I am working on a 'reset' mechanism to unlatch any of the other buttons.
The idea is that the button you push, ...
2
votes
2answers
112 views
Old-school pseudorandom pulse generator (requesting assistance with hardware design)
I would like to design an old-school pseudorandom pulse generator to trigger various types of events (hardware suggestions only please - no programmable ICs). The events that I want to control need to ...
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0answers
62 views
Replacing two corresponding switches as one with logic gates, to supply power, around a DPDT relay
This is one section of a project I'm working on. A user can choose between DPDT functionality (so having "DeviceI" be a motor that goes forward and reverse) or the alternative option to add another ...
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0answers
71 views
Trick/insight to I implement given boolean function with minimum numbers of given gate
I solved bunch of questions which give some function and then ask to implement it with minimum number of gates of specific type, each having specific number inputs. I was making mistakes in all those ...
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1answer
31 views
Finding drain voltage for a resistor loaded CMOS inverter with 0V at input terminal
Introduction:
The following example is from the textbook Sedra/Smith Microelectronic Circuits. It is stated in the solution to this example that since both \$Q_n\$ and \$Q_p\$ are both matched and \$|...
0
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1answer
97 views
I don't understand why this open collector not gate needs diodes
I'm trying to understand why the following circuit, which corresponds to an open collector not gate, needs to use two diodes. The circuit I'm taking about is below:
I think I understand the one just ...
5
votes
6answers
2k views
Logic: Output a 1 when a = 1 and b = 0
I'm a hobbyist just discovering logic gates and would like to know, is there a logic gate that will only output a 1 when a is a 1 and ...
