Stack Exchange Network

Stack Exchange network consists of 174 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.

Visit Stack Exchange

Questions tagged [logic-gates]

Symbolic representation of ideal devices implementing boolean functions

0
votes
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
0
votes
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 ...
-2
votes
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
votes
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). ...
0
votes
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 ...
-2
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
votes
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, ...
0
votes
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 ...
0
votes
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
votes
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.
0
votes
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....
0
votes
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 ...
0
votes
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
votes
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: ...
0
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 ...
0
votes
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!...
0
votes
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
votes
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
votes
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
votes
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?...
0
votes
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 ...
0
votes
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 ...
0
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
votes
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
votes
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
votes
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 ...
-1
votes
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
votes
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 ...
0
votes
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 ...
0
votes
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 ...
0
votes
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
votes
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?
1
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 ...
0
votes
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 ...
0
votes
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 ...
0
votes
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
votes
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 ...