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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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29 views

Dual Comparators connection that affect the design

If we use a dual in package comparator Example LM2903 and do use only one comparator, what should be done with the other one. It is sure that paralleling the two comparator will cause instability and ...
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43 views

Solar power pump - Design critique and help

Okay so, I have a design that 'works' on the breadboard. But I feel like it could use some improvement. Here is my current design: simulate this circuit – Schematic created using CircuitLab ...
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2answers
56 views

window comparator with TLV3402

I made a simple window comparator like this: I'm using LM293, R1 and R2 sets a Vlow and Vhigh threshold, when input is inside Vlow and Vhigh, both leds are off, when input is above or below, one of ...
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1answer
60 views

Relaxation Oscillator Issue, comparator self-oscillating at 25 MHz (40ns propagation delay)

I have a relaxation oscillator circuit, which is supposed to oscillate around 6 MHz, and mostly it oscillates in a very stable manner around it. However sometimes it starts to oscillate at 25 MHz, ...
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2answers
57 views

Hysterisis - How do you choose a good value for R3?

simulate this circuit – Schematic created using CircuitLab Above is the basic schematic for a comparator with hysteresis. Determining the values of R1 and R2 is fairly straight forward. They ...
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2answers
58 views

Comparator as a current detector

I'm looking for a simple circuit that uses only a comparator (or an opamp) to detect the presence of a small current through a high-side current resistor. The idea is for a microcontroller input to go ...
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3answers
52 views

Coilgun - IR sensors interference

I´m working on my coilgun prototype, but I have troubles with IR sensors for projectile detection. When any of accelerating coils is switched off, all sensors report false detection. I´m using this ...
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1answer
51 views

diodes at the output of window comparator

Can anyone explain to me the function of those two diodes?
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11 views

How to simulate a comparator in Simetrix/SIMPLIS

I am trying to generate a square wave using a comparator and I am trying to simulate the whole circuit using the software Simetrix/SIMPLIS. This is the circuit I am using: The first part uses a ...
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64 views

wrong frequency of LC based generator with LM311

I have a problem with the frequency of LC meter based on comparator (a very popular solution, similar to this one: http://www.vk6fh.com/vk6fh/lc_meter_vk6fh.htm). I have recreated generator part in ...
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44 views

Spurious oscillation frequency of relaxation oscillator in between reboot

schematic:- c16 -> 0.1uf c17 -> 10uf R10 , R11 , R12 -> 4.7k R -> 20k c -> 47pf pcb layout:- on every reboot FREQ1 is either expected value of 600khz or its around 25mhz. If its 25mhz it stay ...
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54 views

How does the comparator set the motor speed at a fixed level?

How does the comparator below sets the motor speed at a fixed level? I can think that the comparator output will turn ON if the speed proportional generator output voltage is lower than the zener ...
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1answer
41 views

sine wave to square wave using LT1017

I am trying to convert sine wave of 50 Hz and 10 mV to square wave of 10 mV of positive side only. I used the following circuit. But the square wave has higher voltage compare to my requirement. ...
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1answer
58 views

How to detect low RTC battery with low extra battery load?

I want to detect low battery in typical DS1307 circuit with microcontroller. My first idea is to connect one of low cost comparator inputs to Vbat, another input to 2.0V from some voltage divider ...
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36 views

how to power up a subtractor using a window comparator?

I'm making a circuit that will detect whether a voltage(V1)is in between the range 1-2 V. If so I want to switch ON a subtractor and output V1 - 1 V. I initially thought of connecting the output of ...
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0answers
44 views

Comparing sine wave and triangular for spwm using comparator

i am trying to generate sinusoidal PWM by comparing sine and triangular wave. First i just tried to compare sine wave with reference voltage in order to check the working of op-amp. I get a problem ...
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5answers
2k views

Operational amplifier as a comparator at high frequency

I am trying to generate a sinusoidal PWM signal using analog circuits. I want to compare my sine wave and triangular wave using an operational amplifier (LM741) which has a rise time of 0.3 µs ...
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1answer
81 views

How to use a low current signal to activate my circuit

I'm building a small circuit that needs to be powered by another device. I will power my own circuit from the already existing devices battery. I need to be able to shutdown/power-up my circuit ...
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2answers
72 views

Design Considerations for comparator with ~1mV accuracy?

I am working on building an "exploded" analog to digital converter (ADC) (tracking type: up-down counting) for teaching purposes. I am working with a 0-5V reference, and 12-bits of precision (values ...
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3answers
109 views

UVLO for Energy Harvester circuit

A good background on the problem can be found in the document: (Under Voltage Lock-Out Design Rules for Proper Start-Up of Energy Autonomous Systems Powered by Supercapacitors). The above document ...
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2answers
544 views

How are such low op-amp input currents possible?

I understand that op-amps have low input currents; that's one of their defining characteristics. But looking at the datasheet for the LMC6001 (amusingly called an "Ultra, Ultra-Low Input Current ...
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1answer
66 views

window comparator understanding

I dont understand the output of the window comparator. How does the window comparator switch from HIGH to LOW. There is no transistor or anything else. Only two OPAMP which outputs are put together. ...
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0answers
38 views

Comparator resolving input voltages close to vdd

I have a design problem to solve. The problem statement goes as follows: "Design a clocked comparator resolving input voltages close to vdd dissipating less than 100 uA". What does "resolving input ...
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1answer
87 views

where to connect the offset nulls in a comparator circuit [closed]

I made this circuit but no matter what the input Voltage is, the output stays high and the led lights. Is it because of the offset voltage ? And where to connect the offset nulls to make the output ...
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1answer
74 views

Adjusting duty cycle without affecting frequency of a VCO

I've looked around the internet for a simple voltage controlled oscillator that is able to produce various waveforms in phase with one another. I asked about it in this site and was directed to a dual ...
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3answers
163 views

LM339N - Comparator #4 not working as expected (always low)

I've designed a circuit for a battery indicator for my 18V Li-ion battery pack, based off this example here: https://www.electroschematics.com/8347/24v-battery-level-indicator/ I have it laid out on ...
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1answer
70 views

Analog Comparator Design

I've been brushing up on my analog design, and have some questions regarding improving the design of a simple comparator. It's been a while since I got this deep into it. I'm trying to implement it ...
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2answers
65 views

Why the don't the theoretical and practical output of comparator match for small input?

I have been using TL084cn IC which is basically an amplifier IC. I was giving the input to it of amplitude around 450mv. This IC is capable of providing a slew rate of 13. The Vcc given to it ...
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5answers
134 views

Schmitt Trigger hysteresis

I am studying comparators and Schmitt triggers. And I did not find anywhere how to choose the value of hysteresis. I understand its purpose and I know how to calculate it. But what value is needed for ...
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1answer
44 views

Basic circuit to turn on LED when input detects signal (for guitar)

I'm looking for a basic circuit snipping which can either turn on an LED or give a positive voltage when input signal from a guitar is detected. Basically, I have an existing circuit where an effect (...
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1answer
49 views

How to interface a passive inductance sensor output (audio-level signal) with Arduino?

Would like to interface two passive magnetic-inductance sensors output (audio-level signal) with Arduino. The sensor circuit comprises of two wire-wound sensors and has no power. It generates it's ...
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4answers
59 views

Comparator with Alternate LEDs

I want a simple comparator circuit that lights one LED when voltage is above ~1V and lights the other when below. I'm sure I'm missing a basic concept, but it seems like this circuit should have that ...
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2answers
45 views

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
59 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
91 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
96 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
119 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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138 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
77 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
155 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
88 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
136 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
89 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
29 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
81 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
146 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
94 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
142 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 ...