Questions tagged [comparator]

A comparator compares two voltages or currents and switches an output to indicate which is larger.

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Voltage appears on comparator input

I have made a pcb . A part of the circuit is the Schmitt trigger comparator seen above . The positive feedback resistors are chosen to give the noniverting input values from zero to 0.5 volts . ...
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2answers
62 views

Op Amp Output Voltage

I have a question about an LM741 op amp IC. I am using the op amp as an comparator (open loop with no feedback), as seen below: When the op amp output is low, the output voltage is still around 1.2v....
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1answer
104 views

Extremely simple OpAmp comparator circuit not working

I decided to make my own ADC and I tried to use the following circuit to do it. According to my knowledge, when a 5V signal is applied to the mosfet gate and then pulled to ground, the capacitor ...
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1answer
118 views

Confused about this simple Comparator Circuit Output Waveform

Below is my Circuit and Voltage Waveforms for the Comparator Circuit. My question is -- In the Highlighted area in the waveform - why is the V(CMP_OUT) not high since inp_u2 (blue) is higher than ...
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1answer
150 views

LTSpice - Voltage Comparator not working

My question is - why is CMP_OUT not going to HIGH (i.e. to 12V, P12V_IN) when INP_U1 is greater in voltage than INP_U2. I think I haven't wired the LT1011 right. Do I have to do anything with the "B" ...
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3answers
58 views

Is there a circuit that outputs high indefinitely once one high is received by the circuit? [duplicate]

Apologies if the question is worded oddly/weirdly, but specifically I have a comparator with an unstable output which I know could be fixed with hysteresis, but I would rather just have some circuit ...
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0answers
139 views

Why does my LM393N (dual comparator) ignore its inputs completely when used with an LED?

I have made the following circuit: Viusalisation (not working): https://i.stack.imgur.com/tDA85.png Circuit (working): simulate this circuit – Schematic created using CircuitLab Left to ...
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2answers
91 views

Use ADC as Analog Comparator (AttinyAVR)?

I have recently been trying to transition from Atmel's Atmega 328p avr to the newer (and much smaller) attiny416. The trouble is, the 416 only allows you to choose between two positive inputs and two ...
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2answers
182 views

How does this precision full wave rectifier work?

I am making a VU meter, and I need to rectify the audio signal for the IC comparator chip. I found this circuit in the datasheet, but I am unsure of how it works. I understand that the LF351 op amp ...
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1answer
97 views

OP amp Comparator not working any tips?

I´m running out of ideas here. I have a device that should always output a 5v signal, with a maximum tolerance of 100 mV (4.95 to 5.05 V). I´m building a "tester" device. My tester will compare the ...
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4answers
160 views

Clamping negative voltage on comparator input (LM393)

I need to compare a AC voltage against a reference voltage. I'm only interested in the positive part of the cycle so I need to clamp the negative part of the cycle to protect the comparator input. I ...
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1answer
101 views

How does this Current Comparator Circuit Work?

I have a quick couple of questions about this circuit: The schottky diodes are obviously for minimizing slew delay but how exactly do they do this? If the non inverting input is tied to ground and ...
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1answer
33 views

Voltage alarm with LT1017

With help of this site, I have redeveloped my voltage alarm circuit (see my previous question for the history). I started off with an 741 Opamp and it did not work as I wanted it to work (Thanks for ...
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1answer
96 views

How do I make a discrete voltage detector?

I would like to design a circuit which has outputs LOW when the voltage it is connected to is below a threshold, like 3.3V. There are some ic's you can buy to do this, but I would like to make my ...
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1answer
156 views

Inverting, single-supply comparator not working as expected

I am trying to convert an input sine wave to a square wave. The sine wave is centered at 2.5V and has an amplitude of 2V, with a frequency of 100kHz. I am looking for a hysteresis of 100mV centered ...
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1answer
108 views

How to use comparator functions of 74LS181?

I'm experimenting with the 74LS181 ALU (see here if you like), and it is going well, but I am unable to figure out how to use the A=B, A>B, and A<B comparator functions. The datasheet states, "...
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1answer
41 views

comparator isn't behaving as it should

simulate this circuit – Schematic created using CircuitLab The output is always outputting 5V, and I have no idea why. I have checked the inputs to the comp, I even switch them around its never ...
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1answer
156 views

COMP2 to trigger One-Pulse mode on STM32L1

I am trying to use the output of COMP2 to trigger the One-Pulse mode of a timer (in my example TIM4, but it's quite flexible if it needs to change to another timer) on the STM32L1 series. In the ...
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1answer
163 views

Need a circuit to convert 230V sine wave into 5V square wave

We have already obtained our result using transformer for our college project ,but can't find circuit to convert 230V sine wave into 5V square wave which is supplied to microcontroller. Edit: Our ...
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1answer
84 views

PWM Comparator types for Class D

I've started simulating a Class D amp, but it seems the MAX999 (I saw recommended elsewhere on this site) isn't working. Could anyone point me in the direction of why? I swapped in an LM311 which ...
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2answers
59 views

High resistance op amp

I'm making a simple op amp circuit to use it as a compactor. I connect the non-inverting point to a simple circuit and the inverting to a 3 volt dc supply. the circuit should compare the voltage at ...
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1answer
137 views

74ls148 to 7447 to 7-segment connection. Why is it showing output 0-7 only

We have a project that requires the use of comparators, 74LS148(For Flash ADC), 74LS47 and a 7-segment digit display to show numbers 0-9. The problem is that it only shows an output of 0-7 in the ...
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3answers
135 views

Common-mode voltage outside the specified range

I'm reading the datasheet of TL331. Here a summary of the relevant specification for my question: ...
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0answers
40 views

How do I draw the truth table of an adder/subtractor that sets flags, and those flags are the inputs of a comparator?

How do I draw a truth table of a circuit that : starts off with a full adder/subtractor outputs the result F based on the two inputs (add if opcode is 0, subtract if opcode is 1) then output three ...
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2answers
129 views

CMRR of Comparators

I have been looking around for the Common mode rejection ratio value on the datasheets for comparators but there don't have one. Why is this? This ratio is crucial in terms of choosing a particular ...
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3answers
125 views

Photodiode gate circuit noise

I'm building a chronometer for high speed projectile speed measurement. Currently i'm in the process of designing the projectile detection gate. It needs to be able to detect obstructions in light for ...
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4answers
148 views

How can I modify this circuit for some hysteresis and better design?

I need to make a circuit even when the push button pushed and released very fast, the final output will stay ON at 12V for roughly a second. %10 accuracy for the timing is fine. An LED will indicate ...
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1answer
109 views

How can I use a comparator in a circuit?

I am learning about how to use Operational Amplifiers as comparators. I understand that comparators are used to compare an input signal to a reference voltage. However, I am having a hard time ...
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1answer
41 views

-Ve feedback comparator and its threshold values?

I was trying to analyse and understand the following circuit. My intention was to calculate the hysteresis of the comparator. Circuit working: For both compartor input, there will be voltage inputs ...
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2answers
38 views

Should analogue multivibrator and comparator pullup circuit have separate supplies?

I have managed to produce a design within the falstad circuit simulator for an analogue "LED chaser" using an analogue multivibrator and 3 comparators inspecting the voltage of one side of the ...
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1answer
155 views

How to pick a voltage comparator switch for a low power circuit

I am finishing up an embedded project for my vehicle and the last step is to make it automatically power off with the car. The way I detect whether the vehicle is on or not is via a battery pin, which ...
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1answer
188 views

op-amp comparator 0 or 12V output

I am trying to understand how the circuit shown below works. More specifically, I am trying to understand how the comparator outputs only 0 or 12V. (the circuit is from this paper. Without the 2.2K ...
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0answers
45 views

Voltage Divider for Comparator Threshold

I am trying to understand how the voltage on the negative pin of U2A of the below circuit is 1V/2.4V. From the author: "Threshold signal is 0V/5V but it changes ...
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1answer
62 views

How to use two USB power banks

I want to use two USB power banks for a camera to get longer battery life. Was thinking when the first one is drained, I would have a relay switching over to the other bank, using a comparator for ...
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1answer
89 views

LM339 Incorrect Behaviour for Two Elements

I am designing a monitoring circuit for a battery powered device that is charged from a solar panel. The circuit uses an LM339 to indicate the input voltages via two dual colour LEDs, one for the ...
2
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2answers
307 views

High-speed Infrared UART link with photodiode

I need short-distance (about few centimeters) wireless IR UART link with 250k+ baud. I tried to use phototransistor (assume Q1 is phototransistor). Q3 is used to prevent inverting signal. simulate ...
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3answers
106 views

How to turn on/off a converter using OpAmps

I am designing a controller board for turning a DC/DC Converter on when the voltage level is below 24, and turn it off when it's above 29. With this circuitry I'll be turning it off above 29V. I can ...
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4answers
442 views

Pick largest of several voltages with analogue comparators

This is not an XY problem. I have already decided that the best way to handle the actual application is to use a multiplexer and ADC/MCU to measure all the voltages. However, I am always keen to find ...
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2answers
94 views

OpAmp Comparator Circuit Design for High/Low voltage measurement

I am new to this. I want to make a circuit to measure the voltage from (0 ~12 V), which can have 2 op-amps as comparator to give the output positive, when the voltage goes from 8 V to 12 V and give ...
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1answer
139 views

Autopilot gradual failure--help me guess what might be going on

Executive summary: Old autopilot for a boat, now drifts constantly to the right; I'd like suggestions on what might be wrong, and what some of the parts might be. Details: I've got an Autohelm 3000 ...
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3answers
95 views

Using Comparator

I have a comparator: AD8651 that I am trying to use to switch on my relay (relay is rated at 5V). I have a 5V supply that I am using and I am just using a function generator to see the response. For ...
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2answers
207 views

VCO from a rectangular and triangular signal generator

I need to create the simplest rectangular and triangular signal VCO I can using op amps. The output frequency should be changeable between 1k and 15k. I should also be able to change the amplitude of ...
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1answer
77 views

Window comparator design using LTC1040

I am trying to use LTC1040 as a window comparator(Since I have it) with upper limit of 39.2V and lower limit as 24V. The problem is it has two op amps with 4 inputs each and I can't understand whether ...
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1answer
73 views

Setting Over voltage and Under voltage limits for LTC4364

I am trying to set under voltage, over voltage and over voltage clamping limits in a circuit for Overvoltage Output Regulator with Reverse Current Protection using LTC4364 device. The LTC4364 uses an ...
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3answers
146 views

What builds up a comparator?

I'm trying to understand how comparator (used in 555 timer) able to compare two voltages. I'm searching for comparator schemantics but all I get is the triangle symbol. AND gate has a symbol "D", ...
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1answer
61 views

Arduino VIN and usb toggle circuitry

Link to the schematic on arduino's website.From my understanding there is a comparator circuit in the arduino Uno schematic which turn off USB supply when there is a Vin present of greater than 7V by ...
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1answer
107 views

MCP6548 comparator circuit isn't working

Hey guys back at it again, sorry. I am using a standard MCP6548 Comparator to finish the first stage of my project. simulate this circuit – Schematic created using CircuitLab OP's schematic....
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2answers
125 views

What should be the voltage divider resisor values in units?

I'm trying to build a circuit that lights up a LED when a battery connected to it is full charged. I found LM358 lying around so I plan to use it as a comparator. I want a 3.7v using a voltage divider,...
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1answer
412 views

How to compare an AC signal with a DC reference using a comparator?

To answer the title question, the only way I could think of is this but they don't seem to be working. The AC RMS voltage at the input is 33 V and the reference voltage at pin 3 is 2.6 V. Voltage at ...
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3answers
206 views

Battery Tester Circuit with 3 LEDS

I'm designing a small system that uses an ATMEGA328P and a LoRa module that runs on 3.3V using a AAA 1.5V battery. The battery is connected to a Boost Converter which steps up the 1.5V to 3.3V to ...