Questions tagged [comparator]

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

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79 views

Comparator TLV3201 Output never goes high

I've put together the circuit from the TI document Comparator with Hysteresis Reference Design using the same reference voltage to the noninverting input (Vth 2.3V - 2.7V). The Inverting input is ...
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4answers
171 views

Why is the transistor in this dimming circuit getting very hot?

This is a fairly simple dimming circuit using a dual opamp (IC1) as a comparator to control the brightening and dimming of a light bulb. The switch (pin 2 IC1a) is a contact connection to ground. ...
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1answer
30 views

Can you use dynamic comparator in place of static comparator and vice versa?

According to the book, there are two types of comparators, static comparator and dynamic comparator. The dynamic comparator has clock. So can you use dynamic comparator in place of static comparator ...
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1answer
93 views

How does this circuit act as a half wave rectifier?

I'm having trouble to understand how this circuit operates exactly. The op amp is an LM339 from ST (datasheet link). The circuit in question is as follows: The op amp should be a comparator, but the ...
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1answer
46 views

333mV Current transducer - how to read it and protect the Atmega328p input

i have this CT current transducer: it outputs 333mV at 5A full scale. I'm planning to use it in my house/office in order to detect if a load is switched on or off, but i'm worried about how i can ...
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41 views

SCT-013-010 - Pulse on current threshold

I have this current sensor, it has a measuring range of 0-20A and outputs 0-1V. I need to create a circuit that uses this current sensor, and trimming a current threshold (using a trimmer) the circuit ...
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2answers
66 views

How do we justify small signal analysis of comparator while we know that the biasing condition for the input devices are different?

During the real operation of comparator, the input baseline is lower than the threshold voltage. How do we justify small signal analysis of comparator while we know that the biasing condition for the ...
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44 views

Photodiode pulse detect system

We have a laser signal detection system as shown in the figure below. In this system, we want to detect the incoming laser pulse. The MCU will detect the incoming pulse and perform its operations ...
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46 views

AC tachogenerator frequency sensing using LM393 comparator

I'm currently recycling an old washing machine brushed universal 230 V AC motor which has an attached tacho generator, and I'm building a closed loop controller board for it. I'm up to the point where ...
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2answers
50 views

Fixed-direction voltage translators (level shifters) input voltages

I have a circuit that outputs a digital signal to an FPGA on an XEM6310 board. To digitize the signal, a comparator is used with a reference/threshold voltage of +12 V, with its positive rail tied to +...
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1answer
76 views

How to understand the next values of a comparator inverting with hysteresis (Schmitt Trigger)?

I have my test graded and I'm curious about a question, since I think it's badly graded and I may need to request a revision. I have been told there is a comparator inverter with hysteresis so \$|V_{...
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1answer
165 views

Why does the comparator burn in this oscillator circuit?

I have the following circuit: Power filtering: The 330 μH chip inductor has about 10 Ω series resistance. I scoped the powerup to 5 V and the overshoot even with no load was minimal (maybe 300 mV). ...
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1answer
34 views

Finding Diff Eqs for Variable Square Wave Oscillator of Theremin

For a project, I built a theremin using an LM311N as the basis for my fixed and variable oscillators. I wanted to find the period of the variable oscillator by finding the systems of diff eqs ...
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1answer
114 views

LM339 LED voltage indicator behaving opposite of expected

I have built the attached circuit and am pretty confident it is correct with no short circuits. When it's powered up with a 9V battery, all 4 LEDs light up with no input voltage. As the input voltage ...
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1answer
84 views

How can I choose the values of comparator resistors?

I have a circuit that I use as a thermostat: My comparator is an LM393. I calculated the reference voltage and the R3/R4 ratio using the hysteresis calculation tool on this site: calculator So I ...
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1answer
60 views

Are comparators essential in a negative feedback model, cybernetic system?

Since there are no cybernetics.stackexchange, I thought it would be meaningful to ask this to people who would possibly understand systems theory and cybernetics. Can there be a system, a negative ...
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2answers
83 views

Trying to implement a comparator with hysteresis

So here's the circuit: I need to design the comparator with hysteresis. So i saw this video: I was thinking of doing the same on my circuit. Vin will be connected to R1 and RNTC where it will form a ...
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41 views

Measure dynamic comparator's offset voltage

I'm trying to characterize a comparator I built and I am wondering how I can plot offset voltage over time. I would like to eventually add a calibration block that will reduce the comparator offset ...
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2answers
54 views

I am planning to design comparator based on Opamp but I am not getting the exact pulse output in LTspice [closed]

I am trying to simulate this but I am not getting the exact "RECTANGULR" pulse output. Kindly help me to figure out where I am going wrong. I am going to use this circuit as pulse generator ...
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1answer
121 views

Zero-cross detector does not detect all the zeroes

I'm trying to do a zero-crossing detector but it is only able to mark half the number of zero passings. It seems to work fine with input voltages of 10-20V, but when using a +120VRMS it checks only on ...
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1answer
63 views

Suggestions to clarify comparator circuit

I'm confused with the next issue from school that I can't figure out and wasn't able to solve (this is homework already graded, but the teacher refused to explain me). I was asked to design and ...
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1answer
71 views

Sequential LED turn signal

I am trying to build a 4 LED sequential turn signal using the ne555 timer module and some comparators. I am having trouble with my next steps when trying to figure out what is wrong with my design. ...
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1answer
103 views

Why does my output get supercompensated?

I have almost finished a project that was supposed to output a square wave signal with a certain frequency but when I tried to make a small change to the circuit something weird happened to my output. ...
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1answer
49 views

Analog to 3 bit digital converter noise immunity problem

This task, which at first glance seemed simple enough, caused my left eyelid to twitch nervously. And despite the habit of sorting out my simple things on my own, here I have to turn to the community. ...
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1answer
51 views

Improve conceptual intervalometer for rotating potted plants

I'm trying to avoid having my plants tilting or otherwise looking bad after only getting sunlight from one direction. To solve it, I want to make the pots rotate. I'm trying to design a cheap, stand ...
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2answers
197 views

High voltage adjustable constant current source controlled by MCU

Background: I need a microcontroller adjustable high voltage (300V) constant current. Source: High voltage boost converter. Load: Gas discharge lamp (20mA max). Can only be switch from high side. ...
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2answers
64 views

LM339 window not switching

I made a pair of window comparators with a quad LM339, and LEDs on the outputs. The LEDs flickered near the switchover points. So I made a test setup on a plugboard. The LEDs didn't flicker (typical!),...
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48 views

PIR sensor amplifier with minimum component count

I'm new to opamps and I could use some help amplifying a PIR sensor and output to a microcontroller. Minimum component count without compromising performance (highly integrated solutions). Here is a ...
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3answers
238 views

Does it matter how big the pull up resistor is for a comparator?

Does it matter how big the pull up resistor is for a comparator? The datasheet of the LM339 mentions 5K1 for 5 V. The datasheet of the LM393 mentions 3K3 for 5 V. For a 12 V bi polar connected ...
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2answers
91 views

Lm393 output oscillation

So I have designed this circuit to operate a relay in an off grid circuit. When the solar panel charges the battery over 12.9 V the relay is supposed to kick in. But from 12.8 V to 13 V the relay ...
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2answers
160 views

Review my water sensor

Please review my water sensor circuit, let me know any problems, suggestions. I am not sure if it will work. Ref: https://www.homemade-circuits.com/anti-corrosion-probes-for-water-level/
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1answer
89 views

ACS712 over current switch

The circuit is from here. The output logic is LOW at over current. Is it correct? If U2B pin 5 is set to 2V, U2B pin 6 is 2.5V (zero current), OUT is low. Higher current –> Lower U2B pin 6 ...
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4answers
110 views

Switching on and off at different voltage while maintaining states

I am designing my own circuit to switch on / off a 9V motor via solar panel. I am connecting 2 sets of 3.7V 18650 batteries in series, that means the circuit runs on 7.4V. I am also using a generic ...
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2answers
83 views

Switching thresholds for a comparator

Is it possible to use a comparator to detect a negative signal? I have a negative signal that goes from 0V to -1V. I want the comparator to output a logic high when the signal goes below -0.6V and a ...
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0answers
83 views

What is meant by latched comparator?

What is meant by latched comparator? And how can we identify if the given comparator is latched?
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1answer
82 views

Comparator merge analog and digital grounds [closed]

My schematic looks like this: simulate this circuit – Schematic created using CircuitLab How should i connect ground and power supply to comparator? I have some signal which i want to convert ...
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2answers
80 views

How does a level shifter based on a comparator work?

What is the effect of grounding the power rails of an comparator? (I mean grounding V+ and V-) simulate this circuit – Schematic created using CircuitLab I understand this works like the ...
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2answers
101 views

Best way to create LED logic using differential op amp and comparator?

I got this project a month ago and I've been working on it but I just can't seem to figure this out and my professor won't help us. The project is to build a device to correct the patient's walk -in a ...
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3answers
169 views

Soft-start for MOSFET doesn't work as expected

I need a soft-start circuit for an electronic load to avoid sparks at the input terminals when a power source is connected (in this example when SW1 is closed). Below circuit diagram is working fine ...
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1answer
77 views

Comparator outputs negative voltage when Vcc- is grounded

EDIT: Clarified the output I’m seeing at the oscilloscope. EDIT 2: I've changed the input signal to be a different square wave with V_high = 2V and V_low = 0.5V. It seems that I may have a hidden ...
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2answers
106 views

How to scale (0-7V, 15-18V) to (0V, 3.3V) for OTGW project

Introduction There is an open source project for implementation of Opentherm protocol which defines the master and slave circuit for digital communication according to the protocol specification. ...
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3answers
113 views

Circuit to turn everything above 1V into logic level HIGH (5V)

I have a LED in a car and I want to hook up onto it to detect when its on. But voltage for that LED can depend on the intensity of the LED (depends if its night or day). I've measured voltages from 1....
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4answers
135 views

Please help me understand the reason for using this 5V battery and 2k resistor at the gate of this MOSFET

Please help me understand what that V3 source and 2k resistor are doing here. The output from the comparator U4 will form the gate voltage of MOSFET. Because of the 2k resistor, the voltage at the ...
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2answers
74 views

Unexpected voltage shift in zero-crossing detector circuit

I have designed following circuit of a zero-crossing detector, which is supposed to amplify small sine wave signal and convert it to (digital) square wave. It uses one single supply op amp for ...
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1answer
85 views

What is the device shown in the picture below?

Is this a dynamic comparator? I came across this circuit element while reading some IEEE papers. They looked like opamps/comparators but with 2 output lines. The question is pretty noob but I just ...
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1answer
110 views

BC639 16 exploding on custom design

On a board I designed, a transistor, BC639 16, is exploding. A pinball machine has one board that has some design flaws. Its schematics are these: This PCB has 8 optos (QVE11233.0086) that are ...
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25 views

Window comparator with transient detection

I need some advice with over range circuitry I my design. In summary, I need to probe two nodes in my circuit and raise an alarm if any of them raises above approx. 2V peak (in both polarities). The ...
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1answer
378 views

Why is the output not zero for zero differential input?

To start with, I am simulating a StrongARM latch. Surprisingly, the circuit is not giving a zero output for zero differential input. In the circuit, one clock cycle is 2 ns and VDD is 1.8 V. The ...
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1answer
117 views

How to design an offset cancellation circuit for strongARM latch? [closed]

I have been working on a strongARM latch and I wanted to add a subsystem for elimination of the offset. Circuit diagram is attached with this question. For simulation purpose I have added an external ...
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2answers
599 views

From sine wave to square wave

I want to make a square wave generator with an LM311. I have a variable sine wave source from 1Hz to 16kHz. The amplitude can vary between 0.5V to 11.4V. I tried to use the comparator circuit below ...

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