# Questions tagged [comparator]

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

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466 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 ...
101 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 ...
140 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 ...
100 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 ...
239 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 ...
80 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 ...
86 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 ...
147 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", ...
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 ...
116 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....
126 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,...
438 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 ...
222 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 ...
45 views

### LP311 collector remains at ~11V when “low”

Okay, I'm trying to monitor current going to a device, and in case current is drawn, light a led and provide a low signal (<5V) to a microcontroller. The current goes through a half-ohm resistor ...
640 views

### Window Comparator

I am reading this website and don't understand why this circuit doesn't blow up. If Vin = Vcc then seems to me top opamp A1 would drive low (Vcc > 2/3Vcc and inverting comparator) and the bottom one ...
892 views

### Flyback diode is acting weird

I have the following schematic: Vcc can vary from 12 to 15 volts, so the design was intended to switch on the relay through a MOSFET when the input voltage is over 13.4 volts. The actual Zener I've ...
208 views

### LM311P op-amp strange behavior in comparator mode

I'm trying to build a schematic which will turn on a relay in case motorbike battery voltage will reach some level. I've ended up with the following schematic. simulate this circuit – Schematic ...
284 views

### Arduino inductance meter using op-amp as comparator?

I want to create an Inductance meter with an arduino nano, for that I follow that link whose theory convinced me : tutorial (The Diode on schematic remove analog negative voltage, Edit: I have ...
75 views

### Why does this LTC1440 Comparator switch so slowly?

I am trying to build an undervoltage protector for a 6S LIPO battery. My idea was to use a comparator to switch off an NMOSFET when the battery fell below a preset voltage, 20V: R20, R21 and C20 ...
388 views

### Problem with output swing in LM358

simulate this circuit – Schematic created using CircuitLab I am working on a battery charger with indicator. I am using a LM358 to compare the voltage of my battery with a reference voltage of ...
281 views

### How to deal with strobe and balance pins of this comparator for single supply operation?

I want to use this LM311 comparator with a single supply. But these are pins called balance and strobe which confuses me. What are these for? In a forum I read someone suggests pin 5 and pin 6 ...
176 views

### Draw a circuit with a voltage divider, two comparator ICs, LDR sensors

I got this last question to practice for my exam and I got stuck. The question is draw a circuit with a voltage divider circuit, two Comparator ICs, LDR(Light Dependent Resistor) sensor Outputs: ...
274 views

### Questions regarding a comparator circuit coupling to an analog switch

This is directly related to my previous question, so it requires to first have a look at that. And the below LTspice implementation is based on Andy Aka's answer. The following circuit works in ...
101 views

### How can I modify this opamp circuit's logic

I need a system where it follows the input voltage below a set threshold voltage, and it outputs a set voltage above the threshold voltage. Below is my attempt: The circuit shown can output a set ...
291 views

### Problems while using op-amp as a comparator on a single supply

Here's my circuit: . Application: The circuit is for ground fault detection. When a fault current of 20mA flows through the primary of the current transformer (1:660), it generates a current of ~30uA ...
201 views

### Comparing two variable voltages with hysteresis

All of the designs I have seen for adding hysteresis to a comparator (Schmitt triggers) assume that one of the two inputs to the comparator is set at a fixed reference voltage (typically with a ...
732 views

### Saturation problem of comparator [duplicate]

I am trying to design a comparator using a 741 IC, with a single supply of 12V. I have set the reference to 2V and I require the output to toggle between 12V to 0V. but the problem I am facing is the ...
306 views

### Capacitor weird behavior

I have hooked up the following circuit: Also, is there any possibility to create a link for the schematic? After posting it I realized it´s too small to be seen but I don´t know how to fix it. ...
56 views

### Peak detection comparator simulation problem.(Process and no VSS version)

Here is a peak detection comparator schematic and simulation,i have three question about them. 1.Why is there a high signal in C point,but not in A and B point? 2.There is VSS in this peak detection ...
708 views

### How can there even be an input voltage on a long-tailed pair?

Assuming the following: The voltage across the base-emitter junction of a BJT is constant in forward-active and saturation mode The BJTs in a long-tailed pair are normally forward-active or saturated ...
80 views

### What is the best way to design voltage monitor with tri-colour LED?

I've built a power supply with regulated +15v, +12v, +5v, -12v and -15v outputs and I'd like to build a voltage monitor to let me know if any of the rails are above or below their stated voltage. I ...
88 views

### Indicator LED pulling up line

I have a simple circuit: (Note: RN4 is currently 180 ohms. The label got left off the image.) When the 339 is setting an output low, the output is only dropping to about 2.3v, and not 0. Not low ...
46 views

### How does Shift+Turn off disable the circuit of the calculator?

How does it electronically work that in a basic Casio calculator, shift+ ac turns off calculator, is it a comparator that compares these two button states then triggers a transistor?
471 views

### will this timer/delay circuit works as intended with almost equal opamp inputs?

I just saw this video about a so called delay circuit using opamp in comparator configuration. The author mentions to use a pot as a voltage divider to feed the (+) input and the node between a series ...
295 views

### Driving solenoid valve using LM358 as comparator and ULN2003

I'm trying to drive a 12V DC solenoid Valve with following diagram. In 1st block the PC input is compared with 2.2V and its output goes to block2 and ULN2003 for driving the valve. The 2nd block is a ...
88 views

### Voltage Detection via Analog Comparator

I'm currently designing a PCB at which I have an lithium ion battery (4.3V max) attached. The battery is charged via USB (5V). The charging controller is enabled by a microcontroller which should ...
371 views

### A simple circuit to toggle between LEDs based upon input voltage

I’m trying to design a circuit to test a certain component, so I want to have different pairs of red/green LEDs for indicating whether various parts of the component are working. Indication as to ...
59 views

### Why can the offset voltage of the comparator let the transition time be longer or shorter?

When$V_{FB}>V_{REF}$,then the battery enter the CV mode,otherwise,battery enter CC mode,and because inherent offset voltage of the comparator, the transition from the CC stage to the CV stage ...
131 views

### Comparator doesn't swing, is there problem with circuit?

I made this circuit to switch signals based on the 3V regulator sourcing current out VDD (out connector J2), or seeing 3V on VDD coming in on J2. I put the diode to prevent back current into the ...
119 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. ...
93 views

### Fast modulation based on analog signal

I would like to open and close a shutter (acousto-optic modulator) really fast. Really fast in this case means 2 MHz. However, the shutter should not be modulated periodically, e.g. with constant ...
597 views

### Why such analog comparator input setup?

My understanding of an analog comparator is that you have a fixed reference voltage applied to one input and an AC signal to the other input, when the signal's voltage > reference voltage, the output ...
79 views

### Drawing TL094 Quad Comparator in Schematic

Quick question on drawing schematics, when you are drawing a quad comparator into a schematic (such as the TL094), do you use the comparator symbol four times with the IC label by it or do you use the ...
70 views

### IC for magnetic environments

I am working on a comparator circuit for converting a small AC signal to a digital (square) signal. The circuit is meant to be used in a strong magnetic environment, so the casing should not have ...
191 views

### Digital Comparator from LSB to MSB using Lookahead

This is homework to be upfront, but I'm really stuck on it and just need some kind of direction. I've been assigned to create a 16-bit lookahead comparator going from LSB to MSB using no more than 4-...
46 views

### Truncating negative results of Op amp by rail limiting

I have a signal that will swing from -5v to 5v. I am interested in the 0 to 5v part only. I will set a reference voltage and give it and the signal into a comparator. The comparator's rails are 0, and ...
227 views

### Band-pass and LM358 based rhythmic light

I was asked by a friend to build a simple circuit to have a light flash depending on the bass of a song (mainly techno music). This is my idea: The circuit works on 9V to be powered either by ...
1k views

### Simplifying many window comparators

I have 8 thermistors and I must make sure that each of them is inside a temperature window. They all have the same window and I don't care which or how many are inside the valid range, I just need to ...