Stack Exchange Network

Stack Exchange network consists of 175 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.

Visit Stack Exchange

Questions tagged [comparator]

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

1
vote
1answer
197 views

Why does my HV monitor circuit (sometimes) fry components?

simulate this circuit – Schematic created using CircuitLab I have a high-voltage monitor circuit that illuminates an LED when HV is present, shown above. A couple of these boards have worked ...
5
votes
1answer
616 views

Choosing Components for a Discrete Delta-Sigma ADC

I'm going to be designing a discrete delta-sigma ADC to be built on a PCB. I think I understand the basic concept, but I will need to order components fairly soon. Here's my problem: while I have ...
2
votes
3answers
152 views

Considerations when using Opamp as comparator

For cost reasons, I want to use an opamp as a comparator. So far in terms of making sure the opamp is suitable, I have: Making sure the output can slew fast enough Making sure it can handle large ...
0
votes
2answers
89 views

Why does a comparator changes its state when I touch any node at the input? [closed]

I'm connecting LM339 as a comparator and it works well but it becomes very sensitive when the input voltage(at the +ve input) is near to the reference voltage(at the -ve input), It changes its output ...
0
votes
1answer
119 views

Is this AN on comparator with hysteresis wrong?

Reading this datasheet of the LM94022, chapter 8.3, where is shown the following example: I don't know how they get the formulas. I more agree to achieve something like this: taken from this answer. ...
1
vote
2answers
456 views

Input circuit for GPIO of a 3.3v tolerant microcontroller

The micro controller I'm using detects Low for 0-1.8v and high from 1.9-3.3v. The level I need to check is if the input if from 0v-5v stay low, 5v-24v go high on the micro-controller pin( above 1.8v)....
2
votes
1answer
335 views

How to calculate hysteresis when the OPAMP supply voltage is changing

I have designed a GSM/GPS based tracker which is installed at my bike. But it is draining battery too quickly. So, I want to add a cutoff circuit when the bike is not running(battery not charging) ...
0
votes
1answer
164 views

Design of buck boost converter

I'm implementing a buck boost converter. I need a variabe duty cycle with constant frequency of 200kHz(without using a ardino board in which I suppose I would have to upload a program everytime to get ...
0
votes
2answers
134 views

Realize if(0) condition in analog circuit ?

I have a question that I think is really noob-like and I'm dead sure there's a pretty simple answer, but I couldn't figure it out myself and didn't really know what to put into google, so here we go. ...
1
vote
5answers
516 views

Implementing LM339 comparator to count analog peaks

Updates after applying Trevor's advice: I have attenuated the output of the CPS to between 2 and 2.5 volts, as shown in the scope pic: , channel 2 is the constant "high" output from the schmitt ...
0
votes
3answers
652 views

Open-collector comparator with hysteresis and LED indicator at output

I am trying to choose the correct resistor values to make Vout go high when Vbatt falls below 18V and go low when Vbatt rises above 20V. I've built the actual circuit and my measured values are 18.0V ...
-1
votes
1answer
342 views

Constant Voltage Load

Can someone tell me am i right? In constant voltage mode op amp compare voltage on noninverting input with voltage on inverting input and when U+ is larger than U- the load MOSFET turns on? If someone ...
0
votes
1answer
431 views

Design CMOS comparator

I made the circuit. like this paper, But It's not working. When you insert the AC input, a square waveform should appear. I can not interpret the circuit well. If you know anything, please answer ...
1
vote
2answers
350 views

LM139 Comparator question

I am new in the world of electronics and am having trouble understanding an example circuit found in the LM139 data sheet. I created the circuit on a breadboard and it does indeed work, but I am not ...
0
votes
1answer
215 views

Help for a comparator circuit immune to noise with an LED indicator [duplicate]

I have the following circuit which uses an LM2903 comparator. But Im not sure if it is designed well enough, and not sure about the open collector output is used correct: THIS CIRCUIT UPDATED AND ...
0
votes
2answers
407 views

Current sensing with Rdson?

I'm fooling around with a PMOS, a Fairchild FDD6637, and pondering whether it would be possible to use Rdson as a sort of shunt-resistance for measuring the voltage drop, to get the amount of current ...
1
vote
1answer
1k views

How to build a 3-bit comparator using a multiplexer?

I need to (in design) create a 3-bit comparator using an 8-bit multiplexer and/or up to four 4-bit multiplexers. There are plenty of examples of how comparators and multiplexers works on the web. ...
0
votes
1answer
501 views

Designing schmitt trigger having two positive thresholds

I have two supplies, V1 and V2. V1 is fix to a certain voltage. V2 is variable and I want to switch the external circuit ON when V2 < V1. For this case I have used OP-AMP as a comparator. But what ...
0
votes
3answers
3k views

Ideal Op Amp model in PSpice capture

I am trying to simulate a comparator in pspice capture student version. The problem that I am facing is that circuit is not working for higher frequencies because the opamp I am using is not ideal. I ...
0
votes
2answers
417 views

How can I create AND/OR logic gates using comparators?

I want to create AND/OR logic gates using comparators which do not consume a lot of currents. I tried to design the gates using transistors as shown below. But, this might draw a lot of currents. At ...
0
votes
1answer
112 views

Will UA741CN as a comparator work below 8V?

I wanted to create a comparator circuit with UA741CN which is only comparator/op-amp I have in my junk right now. I wanted to use it with 5V but no matter what is inverting ref voltage is giving any ...
2
votes
6answers
3k views

What am I doing wrong with this LM393?

I'm trying to learn how to use opamps as a comparator. uA741 was easy, but it's way too slow for an uncoming lab I'm going to do, so I switched it to LM393 instead which is rail-to-rail and very fast. ...
0
votes
3answers
163 views

Temperature Dependent Frequency of Relaxation Oscillator

I built a relaxation oscillator to convert a capacitance into a variable frequency square wave. The passive components have a very small temperature coefficient, but when we change the temperature of ...
0
votes
1answer
616 views

How to make the LM339 IC source current on its output pins instead of sinking current?

I know that the LM339 Comparator IC has a current sinking output. I made a small night lamp with the help of a LDR and an LM339 comparator IC. It worked properly. The LDR connected to the inverting ...
1
vote
1answer
123 views

How should I sense the presence of current in Solar-Supercapacitor circuit?

I am trying to measure the presence of sunlight through current sensor circuit. I don't want to use LDR as it may give a false alarm if something occludes the small LDR window. Will using the board ...
10
votes
6answers
2k views

Comparator: Noisy sine to square wave, how much phase noise?

In a circuit a comparator is used to convert a sinusoidal signal to a square wave. The input signal however is not a clean sine wave, but has some noise added to it. The comparator is supposed to be ...
2
votes
0answers
82 views

LPV7215 comparator misbehaving in simulation

I'm simulating the following comparator circuit using TINA-TI (Version 9.3.150.4 SF-TI). The behavior, however, is not as expected: Hopefully it is clear that V- remains constant, while V+ swings ...
4
votes
3answers
1k views

LM339 Comparator IC is not responding to any input

I came into Electronics through Arduino, so pardon me if my knowledge about non-Arduino circuits is somewhat silly. I am preparing a small electronics project for my school with LDRs to detect light ...
0
votes
3answers
1k views

How is this oscillator circuit supposed to work?

This answer shows a circuit including a LM311N voltage comparator. Its stated purpose is to be a oscillator, allowing identification of an unknown inductor L1. It has similarities to the Free-Running ...
13
votes
3answers
4k views

Why do comparators generally have higher offset voltages than opamps?

I need to compare a signal to a constant voltage; the signal ranges from 0 to 30mV, and I require a response time of 50ns at 250µV difference. The signal is a triangle wave with a slew rate in the ...
1
vote
1answer
178 views

BJT schmitt trigger has linear behavior on negative swings

I am currently building a VCO for an analog synthesizer. The circuit produces a triangle wave by taking a Schmitt trigger output and feeding it into an integrator. The constant output of the Schmitt ...
3
votes
3answers
553 views

Optimizing Resistor Values for Comparator Reference

Curious if there is a general rule for optimizing total resistance values in a voltage divider reference in a comparator circuit. Guessing it ultimately comes down to whether maximizing accuracy or ...
1
vote
5answers
143 views

Simple, low power way to buffer a 500mV threshold signal to an open collector output?

I have a signal that is 0-500mV when low and 600-900mV when high. I'd like to buffer this signal to an open collector output. The output must withstand a maximum of 3.3V be capable of sinking 60uA. ...
2
votes
2answers
397 views

How to chose the right decoupling/bypass capacitor variant for comparator power rails?

I would like to rephrase this previous question, but with regard to comparators. I can't decide if a comparator is a digital or analogue device, but I realise that digital devices might be bypassed ...
2
votes
2answers
641 views

Simulating a comparator circuit

I'm trying to simulate the circuit posted here, which looks like this: I'm running a transient analysis and have the following settings: I expected to get the output as a square wave, but I'm ...
0
votes
0answers
288 views

Latched comparator output higher than supply

I am trying to simulate the following latched comparator (the detail analysis of that circuit can be found here). At low clock frequency (200MHz), the circuit works perfectly well . However, when I ...
5
votes
1answer
2k views

Why is there a short between my VCC and GND in this circuit?

I am doing a project where I am using a FPGA board which connects to a circuit I designed. It has a quad Comparator (LM339N), a few resistors and an LDR; two distance sensors (GP2Y0A51SK0F) are ...
5
votes
1answer
2k views

Why is there a capacitor in the feedback path of a comparator, why is there a resistor on the input?

I am interested in charging a supercapacitor from a solar panel. I saw a circuit on this page by David Johnson. He doesn't let you copy the circuit, but the gist of it is this: simulate this circuit &...
1
vote
3answers
394 views

Do I need buffers prior to a comparator?

I have the following circuit which generates digital noise... The reason for the 2 diodes has to do with stochastic uniformity of the noise output and I don't really want address this aspect. The ...
1
vote
1answer
166 views

Understanding Working of LC Meter

I am trying to understand working principle of the circuit given in the link below : http://kripton2035.free.fr/Resources/lcmetersch.pdf I realized that the circuit is basically relaxation ...
4
votes
5answers
1k views

Is there a name for this kind of comparator?

I have two analog signals, and I need to generate digital signal (to use as an interrupt for an MCU) when the voltages differ more than a certain amount. It's going to be some sort of comparator ...
0
votes
1answer
215 views

Offset in a comparator's input

This is probably a basic question which i'm stuck with: Why should there be offset at the input signals? => We have offset voltage of 1V on both the signals, when i remove the offset i get very ...
2
votes
2answers
2k views

What is the purpose of the Vref in this opamp comparator circuit?

I am designing a simple circuit for a sensork, and this was an example circuit given by the manufacturer. The sensor is a magnetic sensor in a standard wheatstone bridge arrangement. I was wondering ...
7
votes
1answer
818 views

What is the AVR's analog comparator speed?

I need to detect a short pulse (~ 100nS) with the comparator. So I hope that the short zero-crossing pulse will trigger the comparator interrupt, but I wasn't able to find any information upon ...
0
votes
1answer
159 views

How to clip a portion of waveform and pull it to zero level?

I've generated a sawtooth waveform of 5v and i want to allow 1.5v to 2.5 v and rest of the voltage should be detected as zero. I tried using clipper but it didnt get desired result. Is there any ...
0
votes
2answers
339 views

Protecting a comparator's input from overvoltage during power up/down

I'm designing a board which uses a 15V supply for most of the circuitry but also includes a high voltage (HV) adjustable supply that can go as high as 140V. For safety reasons I'd like to detect when ...
0
votes
1answer
1k views

Comparator on an op-amp in a PT2399 delay pedal

I am building a guitar effects pedal from a schematic I found online. Unfortunately the schematic is poor quality and hand-drawn, but there is a diagram of it constructed on veroboard (this is ...
2
votes
2answers
948 views

Adding hysteresis to a window comparator

I have designed a window comparator and am finding it seemingly impossible to add hysteresis. Below is the basic circuit before attempting to add hysteresis. Now I add a feedback resistor to the ...
2
votes
1answer
243 views

Detecting presence of a voltage without drawing too much current

I am working on a microcontroller project for a garage door opener. Rather than supply additional magnet+reed switches or other kind of detectors for sensing whether the door is full-open or full-...
0
votes
1answer
273 views

Connect LM324 to L293D [closed]

I would like to control the motor direction using an LM324(as a window comparator) & an L293D. the two output pins of my LM324 go to the Logic input pins of the L293D. The output voltage of the ...