Questions tagged [comparator]

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

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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 ...
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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
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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
88 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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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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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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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
101 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
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1 answer
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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
79 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
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3 votes
6 answers
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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
125 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
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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
506 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. ...
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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
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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
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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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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
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1 answer
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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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1 answer
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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
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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
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3 votes
2 answers
113 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 ...
George Guo's user avatar
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1 answer
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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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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
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0 answers
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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
156 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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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
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2 answers
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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
117 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
83 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
260 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
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2 votes
2 answers
160 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
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1 answer
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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
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0 answers
41 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
84 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
0 votes
2 answers
79 views

Comparator as a current detector with shunt resistor v2

I have a comparator with a shunt resistor that measures the voltage and when the voltage of 12 V from the source exceeds the Vref (1 V in my case) it switches to "high" output. I would like ...
Simplifier's user avatar
0 votes
2 answers
110 views

Frequency detector/comparator problem

I have recently learned about schmitt and comparator op amps, and I came up with an idea to build a "frequency comparator" (if it is called like this). The function of this circuit is to ...
David Ab's user avatar
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1 answer
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Comparator as a current detector with shunt resistor

I would like to design in OrCAD a comparator with a shunt resistor that will measure the voltage and when the voltage value is exceeded it will flip. I have designed the comparator but I don't know ...
Simplifier's user avatar
1 vote
2 answers
193 views

How does this zero crossing detector circuit work? How can I modify it to work at lower supply voltage?

I've been working on a zero crossing detector circuit for audio modulating a flyback transformer. So far it's working great, but I have a few questions regarding the circuit and its operation. Image ...
Mr. Infinite's user avatar
0 votes
1 answer
428 views

Simulating cmos comparator on cadence virtuoso

I am trying to simulate the following cmos comparator circuit using cadence virtuoso spectre. Here's my schematic on cadence: I am using the following test bench to simulate the circuit with Ibias = ...
ah286's user avatar
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4 votes
3 answers
335 views

LM311 - all the ones I bought seem to be shorted internally. Am I making a mistake?

This schematic was created for an FSAE prototype car, in order to be used to detect if HV is present. It's called the TSAL (Tractive System Active Light), and I based most of the design from YouTube. ...
BHU1 LORD's user avatar
  • 103
2 votes
1 answer
149 views

Where to add a potentiometer to vary input voltage to comparator?

The attached circuit and description was originally from another website. The circuit as it is keeps the buzzer off until the FSR reaches 26  kΩ (light force), then turns it on until it reaches 10 kΩ (...
Jim Kailey's user avatar
0 votes
1 answer
44 views

Lm358 external voltage to output

Consider Lm358 connected as comparator is single supplied with 10V. What happen if some external voltage like 15V appears on output during output high? Can a current through Q7 CB cause opening Q13 ...
Michal Podmanický's user avatar
14 votes
4 answers
1k views

Comparator doesn't compare inputs close to VCC

I made a dimmable light which turns on or off depending on the luminosity of the environment. The schematic is below: My problem is with the LM293 comparator. It compares low voltage levels ...
CaveScientist's user avatar
1 vote
1 answer
68 views

Passively switch power supply

I am planning on having a backup power supply for my ESP32 circuit and, since I am dealing with power supply, I thought that having an active circuit would be a downside (otherwise, who will feed the ...
Guilherme Raibolt's user avatar
1 vote
2 answers
52 views

Do Gate Drivers That Look Like Comparators Have Comparator Inputs?

I do mostly VHDL & signal processing for work, so please forgive if this question is dumb. Consider Texas Instruments' part number UCC27526DSDR. When I look up its datasheet on Digikey (1st page, ...
James Strieter's user avatar
3 votes
3 answers
493 views

Window comparator to drive LED

I’m struggling to build a window comparator circuit where the output is high when the voltage is in range. I do not have access to any kind of inverter. I have tried using an inverting op-amp, but ...
FluffyMuffin's user avatar
4 votes
2 answers
408 views

Generation of a high-resolution triangle wave [closed]

I am trying to generate a triangular wave of frequency ~ 100 kHz and V(p-p) = 4.5 V. Additionally, I also have a tight specification that the value of the peak of triangular wave generated in each ...
Debugger_Op's user avatar
2 votes
3 answers
392 views

Why AP331A comparator doesn't work without pullup?

I was designing a PCB and had to include some kind of analogue signal peak detector, so I used comparator to get +3.3V when signal is above 2V and 0 when signal is bellow 2 V. I chose AP331AWG ...
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