Questions tagged [latch]

A latch or flip-flop is a circuit that has two stable states and can be used to store state information. However latch is normally used to describe a simple storage device while flip-flop is normally reserved for clocked devices.

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SR Latch internal conflicts

it is known that "11" are invalid inputs for a SR Latch. But I do not understand the reason of that. I cannot see the electrical conflict in this structure: If R = 1, its NOR gate will give 0, for ...
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202 views

Can anyone help me to understand what these capacitors do in this design?

I have a circuit design makes a button latch on-off and drive a mosfet. When I energize the circuit Vout that drives thr mosfet is initially low. After pressing the button, the button state changes ...
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BJT Latching Circuit Help

I have build a latching circuit using both a NPN & PNP BJT to turn on and off an LED, as shown below: simulate this circuit – Schematic created using CircuitLab When I built the circuit ...
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47 views

How does this RS-latch with open switches power the lightbulb?

So I'm trying to learn some of the basics in electrical engineering such that I can better understand how computers work and I'm currently reading about circuits with switches, relays, different gates ...
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158 views

How to analyze S-R latch circuits?

I'm trying to understand the circuit below (from the Apollo Guidance Computer), which is two S-R latches connected together. The top input resets the output and the bottom input sets the output. But ...
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57 views

How soft latch power switch in this specific circuit is possible?

I am trying to understand the soft power switch operation of a LED lamp I dissembled. The circuit of the lamp is depicted below. The switch S1 can be considered as a momentary on switch (SPST). The ...
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132 views

Circuit to randomly light one LED or another

I am attempting to make a cheap and simple "quantum-ish" coin flip circuit. My idea is to use something like an SR latch driving two LEDs, and have the initialization be driven by some random event. ...
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51 views

Power Failure Detection Circuit via Flip-Flop

I'm trying to create a circuit that will detect complete power failure. I think I understand what major components I need, but I'm unsure as to how to go about connecting them. My plan is to take 3....
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47 views

How latches are used to implement High-speed VLSI Designs?

I read a article saying "Latch-based designs, however, have smaller dice and are more successful in high-speed designs in which the clock frequency is in the gigahertz" but I am unable to understand ...
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49 views

Finding out the values in a truth table for a SR-Latch [closed]

My task is to fill in this table the output Q by analysing following circuit My suggestion would be: Would that idea be right? in the digital electronics means: S=1 => Q=1 and R=1 => Q=0 Edit: My ...
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104 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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61 views

What is the meaning of a “soft” latch?

Googling for "soft latch" brings up many results, and on this site 12 out of 232 questions tagged latch contain the phrase "soft latch". However, there seem to be ...
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133 views

What's happening to this 3906?

I'm creating a soft-latching circuit for my project, using a 3906PNP transistor and a N-Channel IRLZ44N MOSFET. The circuit is fairly simple; Once switch one is pressed, it brings the gate of the ...
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57 views

Latch-based sense amplifier design using CADENCE Virtuoso 65 nm technology

I am trying to design a latch-based sense amplifier to sense about 55mV voltage difference using 65nm technolgy, it takes differential input, and should get from it differential output too where it ...
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73 views

Feedback signal consumed in VHDL

Hello I'm new with VHDL and I'm trying to implement a JK latch in VHDL using this RTL schema: Where the "latch_rs" is written as follow: ...
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85 views

What's the difference between a hardware register and a shift register?

There are two different wikipedia articles but they don't articulate the difference very clearly. Is the main difference that the shift registry uses a clock?
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237 views

Why are latches level triggered and flip flops edge triggered?

I know what it means to be edge or level triggered but considering the block diagram or logic diagram of inside of latches and flip flops I cannot see what inside them specifies this property of each, ...
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Can 8051's ALE pin be equivalent to ground?

I want to add another port to the 8051 and I plan to do so by connecting port 2 (pins 21 - 28 of the 8051) to the Q inputs (pins 2 - 9) of an edge-triggered latch (74HC574). I will also connect the ...
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Capacitor life hours

Working on an existing product which has had field failures. Design is a short (60ms) pulse is sent via microcontroller to activate / deactivate a latching switch. I have determined failure is due to ...
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262 views

Metastable state when S = R = 1 in SR Latch?

According to wikibooks, under the section SR Latch, S = R = 1 is a metastable state. The following things are mentioned under the heading When both inputs are high at once, however, there is a ...
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55 views

Rising Edge-Triggered Truth Tables

I'm trying to debug some issues in an old (early-90's is old now, isn't it?) circuit, and noticed something in at least two different chip's truth-tables, and thought I'd ask here.. In the 74LS74 (...
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64 views

Question about SR latch timing

I have a question about how SR latches work: To my understanding the real-world implication is that one of the two gates will receive power first and produce an output signal, and they aren't going ...
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46 views

Difference between low signal and no signal for a SR latch?

I am struggling to understand how the SR latch works. When an input has designation 0, this means "low signal" correct? Is this completely different than "no signal"? Doesn't a logic gate need some ...
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81 views

Some questions about a transistor latch?

Below is a latch made up of two transistors: When the base current of Q2 is increaased this increases also the base current of Q1 which in turn increases the base current of Q2 more. So by such ...
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Problem based on Latches (Sequential Circuits)

I am trying to solve the following question: I want to know: If the truth table for \$ Q_{n+1}\$ and \$\bar Q_{n+1}\$ is correct. I have found out the Reset and \$Q_{n}\$ conditions. However, I see ...
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153 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 ...
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72 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, ...
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485 views

Convert a toggle switch into a momentary response

I'm working on a project and I need to use a toggle switch to control a device that expects a momentary signal. What I want is send a momentary pulse when turning it on and off. Ie: swith off to on: ...
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511 views

New to circuits: Creating a toggle button in Logisim using Latch

I have just started doing logic and circuits and I am trying to make a toggle button using a button and a latch. I can't seem to figure out how to make the light toggle instead of turning on when the ...
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174 views

Is it possible to estimate the execution time of an FPGA design?

Is it possible to evaluate the "execution" time of an FPGA design? I think that if you have a design where you only have And, Or, Not, etc. gates, the result only depends on the inputs. But now with ...
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161 views

Momentary Switch NAND Latching IC Burning and (Possibly) Faulty Logic

Problem: My issue is that the momentary switch with NAND latching logic that I have designed is not functioning consistently. It does work as intended at first, but then fails to work after repeated ...
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What is the difference between the circuits?

I found the trigger (latch) circuit: When no button is pressed, the LED does not light, if you press SW1, the LED will light up, and will light until you press SW2. This can work for different values ...
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61 views

Which kind of logic latch for an over-current H-Bridge disable?

I have a simple logic circuit requirement, but can't seem to match any standard flip-flop or latch to my needs (SR, JK, D, MS, level-sensitive or clocked, etc). The circuit is to disable a H-bridge ...
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419 views

Designing an Over-Current Protection Circuit with Delayed Reset

As part of a larger design I am trying to monitor current through a wire and cut it off if it exceeds a threshold. After the current has been turned off it should remain off for a minimum time period ...
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146 views

SR latch conventions

consider this rule: In SR latches using NOR gates the S should be connected to Q and the R should be connected to Q' and for the SR latches using NAND gates vice versa. is this a convention ? or a ...
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361 views

positive edged and negative edged D flip-flops

I want to know that my understanding about D flip-flops is right or not. We have different types of D flip-flops: Some of them are positive edged (0->1) and some of them are negative edged (1->0) ...
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34 views

Set latch and Or gates

I'm really new to Electrical circuits so please bear with me. I studied how set latch works :firstly, input 0 then Q(let's say output and it's 0 i this case) feedback another input resulting output ...
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1answer
475 views

how to make a latching circuit with ground

I have a pump, represented by a lamp in my schematic, i want this pump to be running once i switch the Activate switch, and when ever an alarm(i have 2 different) is triggered (Alarms are ground) the ...
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1answer
168 views

Latching power circuit with short-to-ground switch

I'm trying to build a circuit around an existing switch that allows another component to override the switch state. (Our component is a computer and the feature we're trying to build is remote-...
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100 views

High frequency clock from clocked RS latch

We were taught that this circuit is not of much use as when CLK=1, J=1 & K=1, Q toggles at a very high rate. So suppose I want to make a high-frequency clock, can I use this? Of course, the ...
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Latch with no Vout

I'm working with the WiPy expansion board at https://github.com/wipy/wipy/blob/master/hardware/ExpansionBoard-v1.2/ExpansionBoard-v1.2_Schematics.pdf On sheet 3, there is what appears to be a latch ...
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Transistor latch circuit - what's the capacitor for?

I've been studying this transistor "latch" circuit over the past couple of days and I think I've grasped most of it, but I'm not sure about the purpose of capacitor C1. https://circuitdigest.com/...
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398 views

Latch edge and Launch edge of a clock [closed]

Why does a Destination register starts taking input from a latch edge and not a launch edge
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193 views

How to correct voltage overshoot in clock divider output?

I am trying to make a quadrature phase divide-by-6 clock divider circuit in cadence. I managed to complete the circuit and obtained the correct waveform; however, due to some reason I am getting a ...
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1answer
121 views

Can Latch be used to store voltages? [closed]

What if we put S=5v , R=0v and then detach the latch IC from the circuit what will happen at Q end ?
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122 views

Strange output from latch connected to comparator

I'm trying to make a latch (in ltspice), so if the comparator output (A) goes low, the latch will trigger and C will go high. C should stay high, irrespective of whether A goes high or low after that. ...
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365 views

Soft-latch auto-reset OFF (hold) / ON (press) button, is the schematic correct?

I'm looking to make a soft-latching interface with a single momentary push button. Required features for my build are (edited, sorry for bad description) : Circuit should always start in OFF ...
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4k views

One pulse to ON/OFF bistable latching relay

I've been trying to design a latching relay driver circuit, with using a push-button switch. Basically when the circuit is powered on, first press in push-button switch make the relay SET, then the ...
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518 views

Power circuit with a push button

In my current project, I try to connect a load rated at 5V/2A with a 5V power supply. To avoid plugging and unplugging the supply over and over again, I decided to add a push button. To turn the ...
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589 views

How do I avoid a race condition in SR latch?

I have designed an SR latch using Cd4001 NOR gate IC. When both S and R are low the circuit refuses to stay in previous state even though I am using appropriate dropping resistors. Is there any way to ...