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Questions tagged [comparator]

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

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What's the deal with this comparator's hysteresis?

I have here a circuit designed by someone else to create a 50% duty cycle square wave that leads a current transformer in phase. The CT maxes out at about 1 amp, and the output of the phase-leading ...
theseventhsu's user avatar
3 votes
4 answers
287 views

I need help to identify the negative feedback loop in a hysteresis comparator

Can anyone help me identify where the negative feedback path is? I want to determine the feedback factors for both negative and positive feedback, but it's not clear to me where the negative feedback ...
hana's user avatar
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2 answers
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Solar emergency LED Night light control design: Solar panel, 5 V : 3.7 V 18650 Li-ion or similar as Vref. No negative voltage. Only GND. Which Op-Amp?

Solar charging daytime with 0 V battery output to micro LED chain. At nightfall, solar voltage drops to 0, activating Vout: 3.7 V or alternative Lithium chemistry to power 30 ft (100×) white LED rope ...
Tikun's user avatar
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1 answer
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3.3V regulator and Comparator not working as anticipated

This is my first time designing something like this so excuse my inexperience. My objective here is to create a simple circuit for checking if a particular component is good or has been damaged. From ...
John Lapinski's user avatar
2 votes
3 answers
117 views

How to make minimum propagation delay pulse stretcher?

I want to stretch a pulse of 100mV and 1ns width to 3.3V and 10ns width with minimum propagation delay. I found a pulse stretcher in Linear's Application Note 87 document(https://www.analog.com/media/...
MCav's user avatar
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2 answers
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The problem with hysteresis is in the comparator circuit with a mosfet. Oscillations during switching

In one of the design guides, I came across a circuit of a comparator with hysteresis. I modeled it in LTspice and built the circuit as shown in the figure. However, when I tested it with real ...
Typeof undefined's user avatar
0 votes
1 answer
39 views

Offset of a comparator

I'm confused about the offset of the comparator. Consider a comparator consisting of a pre-amp and an inverter. Does the offset come from the misalignment of the preamplifier's Vocm and the threshold ...
Jack Black's user avatar
1 vote
2 answers
106 views

The internal transistor of LM311 seems to be conducting when it shouldn't

I have the following circuit, which compares two voltages, one of which is the reference voltage. I've simulated it in LTSpice using the model given by TI on their website and it works fine. After ...
ganymede's user avatar
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2 votes
1 answer
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Clock feedthrough in 5T OTAs?

I'm using a 5T OTA as a comparator, and the reference voltage is applied to the gate of M2 by another circuit - I modelled it with a capacitor (100fF) charged to Vref, just for describing my question. ...
Jack Black's user avatar
3 votes
4 answers
180 views

Using a Potentiometer to consecutively turn on 4 LEDs one at a time, while turning off the all LEDs before it

I'm not quite sure the simplest way to describe this and I'm only using LEDs as my example because it's the easiest way to simplify my circuit. I need to use 1 potentiometer to turn on 1 LED, then as ...
ajbubba's user avatar
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1 answer
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Input ranges exceeding rails in opamps & comparators

With opamps & comparators datasheets I've seen, it was typical to show in absolute maximum ratings values such as: $$V_{SUPPLY} (V_{DD} \; to \; V_{SS}): \quad 12V$$ $$V_{DIF\_IN} (V_{-IN} \; to \;...
Tempus Nomen's user avatar
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0 answers
40 views

Flame Sensor Supply Voltage Range

I have this flame sensor module which I am going to use for a project. Upon closer inspection, I can see that the maximum supply voltage of the LM393 comparator IC used is 30V according to this ...
Kailash Kumaravel's user avatar
1 vote
1 answer
70 views

I am trying to detect pulses from an inductive coil

I have a rotating flywheel with an inductive pickup and a magnet passing in front of it a couple of times per rotation. The signal looks like this for low speed inputs of the rotor: Apologies for the ...
bvongunten's user avatar
1 vote
2 answers
197 views

Why is this not working as a Schmitt trigger?

I've been trying to implement a Schmitt trigger using comparators in LTspice. Needless to say, even though I can work with opamps and comparators, I'm totally at lost with using them to make Schmitt ...
Tempus Nomen's user avatar
2 votes
4 answers
554 views

Why doesn't my OP Amp comparator work in LTSpice? (AD8665)

When V2 > V1, Vout should output approx. 5.3V. When V2 < V1, Vout should be approx. 0V. But this op amp seems to always output 5.3V regardless what V2 is. What could be going on here? Is this ...
BobaJFET's user avatar
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1 answer
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LM393 Window Comparator driving LED using 2N2222

I have a circuit im trying to design utilizing the LM393 as a window comparator. I have them in wired or (outputs tied together) but im strugging in figuring out where I need resistors. Looking at the ...
user3182474's user avatar
1 vote
1 answer
154 views

Why use a voltage reference chip rather than a known VCC and resistor? [closed]

To elaborate, I'm making a circuit that converts an analogue sensor output into an on/off state using a comparator. Is there any reason that I should use a voltage reference chip as the low comparison ...
Steam Ranger's user avatar
2 votes
2 answers
94 views

Unpowered LM393 Comparators

I'm working on a battery powered device and would like an LED to come on when the battery is getting low. In the given schematic, the LED is a red LED having a forward voltage of 2V, Lite-On product ...
Chris's user avatar
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2 answers
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Learning electronics on Tinkercad, need help with understanding how a comparator works

I have set up a circuit as in the picture: I do not understand why output 2 of the comparator is 0V, when the input2 + is clearly higer voltage than input2 -. Shouldn't output2 give a high voltage? ...
Corentin Salomon's user avatar
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0 answers
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Zero crossing circuit with phase control

Beginner here. I am trying to make a "zero crossing" circuit with phase control. This is probably not the right name for the circuit. Basically, I have a sine wave (from the power outlet) at ...
DarkBulle's user avatar
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0 answers
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Debugging the triangle wave generation using ISL7044

I am trying to simulate an Analog PWM circuit as shown in this TI application note. Link attached here => Analog PWM TI Report However, I have a requirement to achieve the same using ISL70444 OP-...
Debugger_Op's user avatar
3 votes
1 answer
107 views

Interfacing an LM2903B output to a microcontroller

I would like to connect the output of a LM2903B comparator to my controller to read the output signal. Both the comparator supply voltage +13V and the controller supply 3.3V are referenced to the same ...
Embedded Enthusiast's user avatar
0 votes
1 answer
78 views

Why is a variable resistor (R101) used in this circuit?

This is from a brake system plausibility device for a Formula Student race car. I'm confused why a variable resistor is used in this case and why couldn't there be a regular resistor instead like the ...
Friezer's user avatar
1 vote
2 answers
114 views

LM393 - comparing variable AC voltage (rectified)

I have a variable AC voltage coming from the motor of a scooter, appropriately rectified with a bridge rectifier and large capacity capacitor. The circuit I want to create will be powered by 12v DC, ...
Anasten's user avatar
  • 13
3 votes
6 answers
1k views

Simplify one-time switch made using a flip flop

I'm trying to make a one-time, "turn-on-once" switch. I've made a simpler design before, but I seem to have lost it.  So basically, when the comparator is pulled to high, the switch turns on ...
Zipho Lunika's user avatar
2 votes
3 answers
173 views

Comparator Latch Initial state

I am working on a latching current limiter circuit and as part of it I'm using multiple LM139 comparators to implement a simple SR latch. This specific comparator has an open-drain output. A latching ...
Malte's user avatar
  • 155
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0 answers
30 views

Current Limiting Circuit with Comparator/ Threshold Comparator (current limit) switch Simulation

I am driving a stepper motor with an H-bridge and hex inverter and need to create a circuit that limits the current. I need help designing a circuit with a comparator that detects a current greater ...
Jay's user avatar
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5 votes
4 answers
527 views

When to have a pathway to ground in op-amp/comparator input?

When having a comparator IC, when should I put a resistor in series, to ground, or neither? I have three examples below: I understand ex1 may be useful to reduce offset voltage due to offset current. ...
ludicrous's user avatar
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1 vote
1 answer
213 views

Simple comparator circuit w/ LM311 doesn't work

I'm implementing the comparator circuit below, with the LM311P IC. I changed V_in's voltage from 0 to 9, making it above and below the 10/2 = 5V threshold at the V+ input. I was expecting that ...
ludicrous's user avatar
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2 votes
1 answer
128 views

High value resistor on comparator input

I have a comparator(LM393B) on a preterminated transmission line(50 ohm) which is intended to detect low and high voltages, i.e. off and active levels. Would it be a good idea to attach a high-value ...
lemon's user avatar
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3 votes
1 answer
121 views

Comparator not giving H when sine wave is positive

I have an LM311 with a single supply and an amplified signal which has AC 8Vpp and is centered at around 8V. In the schematic below, I represented the signal as a composition of 8V + 4sin(wt). I want ...
ludicrous's user avatar
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0 answers
30 views

Detecting OLED display refresh frequency using phototransistor

I am trying to detect the refresh frequency of an OLED display driven by an SSD1309 display controller. During the refresh cycle, each row of a frame is charged and driven for 65 DCLKS in a sequential ...
Joshua Dotson's user avatar
0 votes
1 answer
71 views

How does this particular operational amplifier as a comparator work?

The op-amp is super weird and not similar to any other op-amps I have seen. I don't understand how R2 is connected to the 12 V instead of the V out, or where the voltage is coming from, if the sensor ...
Pol Recasens's user avatar
2 votes
3 answers
1k views

How does the resistor on the LM311 comparator output work?

This is the circuit of a GND detection probe that is a part of a PCB under production so it's supposed to be tested and it works: The PINPROBE line is a track connected to the pin of a STM32F103xx ...
Suvi_Eu's user avatar
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0 votes
1 answer
85 views

Resetting and advancing counter using same line [closed]

For a project, I need to use one analog signal to control a binary counter -- to both advance and reset, e.g. +1 V square pulse goes to clock and -1 V pulse resets the counter, or 1 V goes to clock ...
Nikd0's user avatar
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1 vote
1 answer
95 views

LM393 dual comparator outputs are not the same

I applied the same signals to both inputs of the LM393P double comparator. The number 2 comparator output gave the expected result (first photo). However, when I apply the same signal to comparator 1,...
Baris's user avatar
  • 13
3 votes
2 answers
130 views

How to boost the gain of this comparator?

I'm trying to implement a comparator for ADC. The schematic is shown as follows. Image source: S. Lan, C. Yuan, Y. Y. H. Lam and L. Siek, "An ultra low-power rail-to-rail comparator for ADC ...
Jack Black's user avatar
0 votes
1 answer
104 views

Strange comparator behavior

I am testing the following comparator schematic: simulate this circuit – Schematic created using CircuitLab I've replaced the original 280 kΩ resistor with R1 and trimpot R3. The hysteresis ...
Maple's user avatar
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0 votes
2 answers
94 views

Reduce component count for BCD input error detection

I made this circuit that reads the input of the DIP switches and detects if the input is an error or not a BCD value. The problem is I have 4 inputs for my circuit. The LED indicate if the input is ...
Noobielectrix's user avatar
0 votes
0 answers
57 views

DC analysis of a CMOS comparator

I'm designing a strongarm latch comparator in virtuoso using gpdk90 and I'm not seeing what I'm doing wrong while doing DC simulations. I want to extract the comparator's offset but the output is ...
Scully's user avatar
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1 vote
2 answers
159 views

Voltage comparator approach

I am building a self biased tube amp. It has an adjustable negative bias of about -32 to -67 Vdc for various tubes. The power supply side has some bult in safeties to make sure there's always a ...
Hoops's user avatar
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0 votes
1 answer
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Convert NIM logic levels to LVDS

For my application, I need to convert a negative voltage pulse which is in NIM logic ('1' is -0.8V, '0' is 0V) into LVDS signals. The other part of the problem is that a pulse width is approximately 0....
Murfoll __'s user avatar
0 votes
2 answers
37 views

How can I use a microphone with integrated PA for a level detection purpose?

I have a MEMS microphone with an integrated PA. I'm going to use it as a trigger in a low-power device so I wanted to know if that internal PA is enough and I can connect it directly to the analog ...
Tirdad Sadri Nejad's user avatar
1 vote
2 answers
132 views

Comparison of two numbers of different length

I want to design a circuit at block level using IC 7485 to compare one 6 bit number with another 5 bit number. My approach is: Put the most significant bits into the four 7485 comparator inputs. The ...
Arinjoy Pramanik's user avatar
1 vote
1 answer
88 views

Can an output voltage of a simple comparator be higher than the input voltage?

This is a simple comparator circuit that I have built for a school project. However, for some reason, the output voltage tends to be higher than the input voltage of 12 volts(accidentally cut out in ...
Hyuntaek Woo's user avatar
0 votes
1 answer
439 views

Sizing an CMOS StrongArm Latch comparator on Virtuoso from scratch

I'm currently designing an CMOS comparator and I'm a little bit lost regarding sizing the transistors. I was taught to use the Id formula, but for that to work I need to have muCox, and I do not. Can'...
Scully's user avatar
  • 3
2 votes
2 answers
170 views

LM393’s LOW shows high Ohm to GND

In LM393 datasheet it’s connected to GND on LOW, and disconnected of everything on HIGH. But on my tester I see on LOW: 100 Ohm when no load’s GND connected to Out pin. (No load at all). 850 Ohm when ...
juanmf's user avatar
  • 135
0 votes
1 answer
55 views

Comparator connection with SR latch v2

I designed a comparator that sets 12 V on the output whenever there is overvoltage on the input of the comparator (13 V from AC sin source). In my schematic, the output value of the SR latch reacts to ...
Simplifier's user avatar
0 votes
0 answers
43 views

How do I make a gate with only one condition?

I need a simple gate with one condition only but with two ends, if its given 10V it will deliver a square wave from an oscillator I've built, if not then it will deliver a wave from a signal generator,...
ricsrdo.casro's user avatar
0 votes
2 answers
191 views

What is this comparator in the Arduino Uno Revision 3 doing?

I was looking into the schematic of the Arduino Uno Rev3 particularly the built-in on board LED (connected to pin 13) and was curious about what was happening. Here you can see pin 5 of port B being ...
First User's user avatar

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