Questions tagged [comparator]

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

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18
votes
5answers
27k views

Difference between differential op amp and comparator

What is the difference between a differential op amp and a comparator? I know a comparator can only give me two values (the supply values). The differential op amp amplifies the difference between ...
9
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1answer
467 views

What is the difference between “opamp” and “comparator”?

In electronic part seller websites, I see that there are two separate categories for opamps and comparators. As far as I know, an opamp itself is already a comparator if you don't connect a negative ...
4
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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 ...
6
votes
1answer
13k views

Can someone explain how this transistor comparator works?

I am looking to make a comparator using transistors and I stumble across this circuit claiming to be one: Unfortunately, the description that came along with it leaves a lot to be desired, ...
3
votes
1answer
9k views

Generating sawtooth signal out of square/triangular signal

I want to create a sawtooth signal generator. I know, how to build op-amp comparator to create a square wave. I also know, how i can get triangular signal by integrating comparator output with op-amp ...
12
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2answers
5k views

comparator schematic symbol

This schematic appears in a recent question. The triangle may be an op-amp or a comparator, because they both have the same connections. (Why) isn't there a separate symbol for a comparator? The ...
5
votes
4answers
7k views

Why do they usually make comparators open collector?

I never see open collector opamps while I frequently see open collector comparators. What is reason for preferring open collector output in comparators? (Inside of LM193.)
3
votes
2answers
1k views

Dynamic Braking resistor chopper circuit

I want to design a standalone dynamic braking circuit for AC motor driver , because to deal with regenerative energy that the AC source cannot handle causing a DC bus voltage Rise . The concept is ...
5
votes
1answer
2k views

Hysteresis calculation for “open-collector output comparator” with a pull-up resistor

Standard comparators such as LM2903 and LM311 have open collector outputs. I see many times the output of these comparators are tied to Vcc by a pull-up resistor (e.g. in a Schmitt trigger case). ...
4
votes
3answers
3k views

Help with a simple comparator circuit

I'm trying to build a simple temperature controller by using a thermistor and a potentiometer attached to a Schmidt trigger to control a relay. I realize that I have some serious design flaws in ...
1
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2answers
1k views

How to make an h bridge using only comparators

I discovered I could easily make an H-bridge (or something that effectively behaved as one) by cross coupling the inputs of two op amps. So for op amps 1 and 2, 1+ is connected to 2- and 1- is ...
1
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2answers
2k views

How to make a digital comparator with multiple inputs?

I have been attempting to make a digital comparator but I am struggling to get in more than one input. The idea is that I have 2 sets of 2 numbers (4 inputs total) and I want to have the output take ...
0
votes
1answer
388 views

Low level sine to pulse converter with sharp rising-edges

I have two circuit simulations: Circuit1 and Circuit2 which are shown in above schematics. For the sake of simplicity I drew them in the same schematics. They share the same 12V voltage source and the ...
0
votes
0answers
56 views

Peak detection comparator simulation problem.(Process and no VSS version)

Here is a peak detection comparator schematic and simulation,i have three question about them. 1.Why is there a high signal in C point,but not in A and B point? 2.There is VSS in this peak detection ...
14
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 ...
13
votes
1answer
3k views

Can I use differential I/O pins of FPGA as high speed comparator?

High speed comparators are rather expensive and speed is what FPGAs are very good at. On the other hand, FPGAs (in my case: XC3S400) have paired differential pins in each bank that their voltages are ...
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 ...
6
votes
2answers
12k views

Comparator with hysteresis equations

I'm trying to be sure I'm computing the values for this circuit right. Here's an example of the circuit I'm trying to build (it's going in a 12 V DC system, so I filled that in already). I have ...
5
votes
1answer
7k views

Negative feedback capacitor in Op-Amp comparator circuit

This is a part of a circuit of a big device. I'm interesting why need for C1 capacitor? OA2 is a general purpose opamp. Power supply for the opamp is +15V/-15V, sorry for mistakes in the picture. ...
4
votes
4answers
13k views

Can you feed in a voltage higher than your supply to the input of an opamp?

I have a 28V digital signal. 28V being logic 1 and 0V being logic 0. Can I feed the 28V into an opamp (Vcc @5V) to level shift it ? Or will I have to create a voltage divider to bring the 28V < ...
0
votes
2answers
101 views

How can I modify this opamp circuit's logic

I need a system where it follows the input voltage below a set threshold voltage, and it outputs a set voltage above the threshold voltage. Below is my attempt: The circuit shown can output a set ...
1
vote
1answer
4k views

LM339 basic operation

simulate this circuit – Schematic created using CircuitLab What voltage needs to be applied at \$V_{\text{in}}\$ for the LED to turn on? My answer: \$V_{\text{in}} > 9\text{V}\$ Is this ...
1
vote
2answers
94 views

High side current indicator/

simulate this circuit – Schematic created using CircuitLab Hi! I am in need to make a high-side current monitor for detecting whether load (R1) is present or not. As currents running through my ...
6
votes
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 ...
5
votes
4answers
12k views

Detecting an open circuit by sensing current flow using a shunt and comparator

I need to detect if a load resistor is taken out of circuit. The load resistor is a photoresistor and can vary from 50k\$\Omega\$ up to 2M\$\Omega\$ and is driven by +5V to ground. The approach 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 ...
2
votes
2answers
847 views

Why does the ATTiny84 have both an analog comparator and an ADC?

I have been reading through the datasheet for the ATTiny84A, and noticed that it has both an analog comparator and the ability to use its ADC in unipolar or bipolar differential mode. From what I can ...
2
votes
2answers
712 views

How can there even be an input voltage on a long-tailed pair?

Assuming the following: The voltage across the base-emitter junction of a BJT is constant in forward-active and saturation mode The BJTs in a long-tailed pair are normally forward-active or saturated ...
2
votes
3answers
2k views

Window comparator using LM339 - invert output

I'm using the LM339 for an application with different voltage ranges. I am using the window comparator circuit since I want to test a specific range (4 - 8V). The circuit shown below actually ...
2
votes
1answer
448 views

MIC6270 comparator - input voltage higher than supply rail

I've read in various places (such as here) that you can't safely feed an input voltage to an op-amp / comparator that's above its supply voltage, even when within maximum ratings. However, the ...
2
votes
2answers
2k views

Battery charging and discharging problem

I have designed a battery charging and discharging circuit. The main purpose of this circuit is to charge the battery and then discharge, one operation at a time. I have also added a hysteresis of 3....
2
votes
3answers
4k views

Three Phase Input to Single Phase Output

We have three phase input and the voltages in the three input is not the same always. Sometimes, one or two or three phase will be off. I would like to connect the phase to output which lies within ...
1
vote
1answer
708 views

over voltage detection using comparator

I need to design a over voltage protection circuit. I intend to use a comparator for the said circuit. The reference will be from a standard voltage ref source. While the voltage at the non-inverting ...
1
vote
3answers
1k views

How to create a zero crossing detector using a full bridge wave rectified circuit

Currently 1) I have a full bridge wave rectified ac waveform of 10Vmax. 2) I also have a potentiometer adjustable DC waveform. 3) My rail voltages are +12V and -12V. 4) I currently supply my full ...
1
vote
1answer
5k views

How to check if a comparator is broken?

I have just started experimenting with electronics and am concerned that I may have destroyed my LM339 comparator circuit. As a basic test, I had a 3.0 volt power supply hooked up to the Vcc pin and ...
1
vote
3answers
851 views

Passing greater of 2 voltages using 5V signal

I need to output the larger of two voltages (Va, Vb) (both of which could be in a range 0-30V), but drive the circuit using a 5V supply. A simple solution (using op-amps, FETs) is needed. I have ...
1
vote
1answer
134 views

Questions on interfacing circuit for an NPN input

I have to use this sinewave outputting sensor with the NPN input of this converter. My previous question was related to the same issue but the question was about a totally different circuit design i.e....
1
vote
4answers
445 views

Comparator output not fully switching on MOSFET

First Question for me. I have benefited from other answers here but have not fully resolved my problem. Here's my problem... The LM311 Comparator output does not drive the N channel MOSFET fully on....
0
votes
0answers
692 views

LM311 comparator : strange output levels [duplicate]

I have the following circuit, where I put R52 = R53 = 2700 Ohms : Schematic http://free0.hiboox.com/images/5013/ac1bae22d71c2e3cc17b4ed3eda3090a.png Triggering levels are of 1V and 2V approximately ...
0
votes
1answer
215 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" ...
0
votes
2answers
275 views

Questions regarding a comparator circuit coupling to an analog switch

This is directly related to my previous question, so it requires to first have a look at that. And the below LTspice implementation is based on Andy Aka's answer. The following circuit works in ...
0
votes
1answer
225 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
1answer
173 views

Safety considerations when using LED and a comparator

I want to make a simple circuit, it uses two comparators to drive two LEDs, it should turn the LED (green) if the voltage is higher than let's say +2.5V. If is lower then turn the first one off and on ...
0
votes
3answers
133 views

inverting comp behaving strange

I am using an LT1716 comparator in the inverting mode. So, I am simulating it in LTSpice. I understand that the Vout is Vcc when Vin,at the inv terminal is less than Vref at the non inv terminal and ...
0
votes
2answers
89 views

What is the use of these resistors in the schematic?

I am trying to build a line-following robot with the schematics I found below. I understood that the comparator is used as the logic for the robot and there is no need for a feedback loop for the ...
0
votes
1answer
286 views

Setting maximum opamp input voltage by zener diodes with respect to supply voltage

When I was about to implement a circuit with a 24V supply voltage I noticed that the comparator's inverting input in the part below receiving 24V with respect to ground when the input signal goes high....
0
votes
2answers
946 views

How to tell when an LM334 is limiting the current?

I have an LM334 based constant current source configured to supply a max of 1 mA. The load has a variable impedance. My goal is to make an alarm of sorts when that impedance exceeds a threshold, and ...