Tagged Questions

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

learn more… | top users | synonyms

1
vote
3answers
129 views

What is the drawback of a high-value resistor for positive comparator feedback / hysteresis?

I'm building a simple circuit which has an LM211 comparator at its heart. The positive input is connected to a 10k-10k resistor divider across the supplies, stabilized by a 1uF capacitor. Hysteresis ...
0
votes
1answer
19 views

Ambient Light Sensor + Comparator

So I've been looking at options to create a way of controlling whether a flash will fire based on the amount of light in the surrounding environment. Early note: Everything has to be surface mount ...
1
vote
1answer
32 views

Comparator input interfacing

I need to digitize a weak (-10 dBm) 1-20 MHz signal with a comparator. The output of the preceding stage is 50 ohm. The comparator I'm using is the LT1715. It's input trip point is ± 5 mV and the ...
1
vote
1answer
68 views

OP amp voltage comparator for an FET

I have a project requiring a switch (I supply 4.8V, the switch stays off. I supply 5V, it turns on.) After some testing and asking several questions, I realized that the MOSFET I was using would not ...
0
votes
2answers
74 views

Opamp comparator output interfacing with digital circuit

I want to use Op amp as a comparator to shape the 50Hz sine wave to square wave, then route it to the PLL reference signal input, the PLL chip is 74HC4046. And i use AC coupled method. Because the ...
3
votes
1answer
151 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. ...
0
votes
1answer
48 views

Using an H-Bridge like a comparator

I'm wondering if there's a way to use an H-bridge like a comparator- That is, if one input is greater voltage than the other, then the attached motor spins one way, and vice versa, and it doesn't spin ...
0
votes
0answers
50 views

LM2903 Comparator output oscillates

I am using an LM2903 Comparator on my design to measure sensor signal. Constant current source is provided to the sensor by means of resistors (connected to 2.5V). I have an RC input filter ...
2
votes
2answers
53 views

Protecting a comparator in a tension measurement device

I am building a device to measure the tension of a conducting wire using an Arduino. The basic circuit concept consists of two stages: The wire is placed in a strong magnetic field. Then the ...
0
votes
1answer
55 views

LC comparator based oscillator

I am trying to build a LC oscillator based on LM393 open-collector comparator, but am having some difficulties. This is the current circuit: I was expecting to get a nice square wave with one ...
0
votes
1answer
50 views

Voltage Comparator Circuit Output 0V or 5V

I'd like to build a very simple voltage comparator circuit with the following properties: Vs = 5V V- = Ground Vout = 5V if V+ >= 200mV Vout = 0V if V+ < 200mV I'm using this comparator: ...
0
votes
2answers
127 views

Thermocouple Simulation Test Circuit and Voltage Comparator Circuit

I have a challenge that I would like to share with you. (at least a challenge for me) The resistor R8 (10 turn potentiometer) can be adjusted from ~0 to 1K Ohm to output voltages from 3mv to 30mv. ...
0
votes
2answers
55 views

Comparator Output Swing Measurement

i wan't to measure the maximum and minimum output swing of a Comparator. I'm using the circuit which you can find attached. However, since the Output of the Comparator (TI LM2903) is open drain, I ...
2
votes
1answer
350 views

What's the purpose of the 1M resistor in this comparator circuit?

I find this circuit from ON Semiconductor's LM211 datasheet. There is a 1M resistor from negative power rail to the 'reference' input. ON doesn't describe the circuit's function. I think it's a ...
1
vote
3answers
120 views

What type of Op Amp or comparator has a schematic symbol with hysteresis like symbol

I already know it is not a schmitt trigger, it looks like it is used as an open loop amplifier taking a reference voltage on the (+) and the V0 is fed into a schmitt trigger. I have no other data. ...
1
vote
2answers
49 views

The direction of the bias current of LM311

I thought the conventional method to denote the direction of the bias current is to precede the IIB parameters with the '+' or '-' flag in the 'electrical characteristic' table, '+' indicate the bias ...
2
votes
4answers
141 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.)
2
votes
4answers
263 views

Is there a clever way to prevent a window comparator from oscillating?

Here is my schematic It's basically a crude battery level detector (I am very aware that this isn't the best way to guage battery life, I'm not here for that) it's not crucial that it is super ...
0
votes
3answers
118 views

Are there examples of chips where comparing 2 against zero would be slower than comparing 1 against zero?

This question on StackOverflow goes like this which is faster - while(1) or while(2)? Asking which of two infinite loops is ...
2
votes
4answers
291 views

Need help explaining this circuit and how it is dimensioned and designed

I'm working on a project to school where I'm designing a battery charger with battery status indicator, and I found this circuit online: but to include it in the project, I must explain how it ...
1
vote
2answers
82 views

High voltage input window comparator

I'm trying to find pieces (comparators or op amp) to make a window voltage comparator. My window range is 180VDC to 230VDC. Did you ever heard of high voltage input comparators? I don't need a high ...
1
vote
1answer
89 views

Why does my comparator not give an output?

I am new to doing electronical things, so I bought some components and I am just trying thing out. Now, I am using a LM 2901-comparator, whichs documents you can find here. Using a power supply of ...
0
votes
2answers
103 views

Handling high voltage input range to comparator

I'm using 3 comparators for sensorless back EMF commutation of a BLDC motor. This involves comparing the voltage of each motor phase to a neutral point to detect zero crossings. See Microchip AN970 ...
0
votes
1answer
74 views

Difference between LM339D and LM339N

Im trying to understand different comparators. What is the difference between different LM339 ICs, especially between LM339D and LM339N?
0
votes
4answers
171 views

op amp as comparator/switch - strange behaviour

I have the following schematic (extract): The purpose of this is to enable a pin (chip enable) and to disable the 5V supply ("5V consumer") if the threshold at the signal IN is above a certain ...
1
vote
2answers
139 views

Op-Amp comparator or amplifier?

My colleagues and I are having a discussion about the circuit below, specifically: Is the op-amp being used as a comparator, or as an amplifier, or something else entirely? The circuit is a negative ...
1
vote
1answer
84 views

Detect a keep-alive signal

Reason/Background I have a raspberry pi (garage) that's doing some security-related monitoring, and generates a "keep-alive" signal. I would like to have an alarm go off in a separate place (attic) ...
1
vote
1answer
48 views

Multisim producing very low comparator output voltage

In the images below I have the same schematic in multisim, one snapshot for each state of the comparator. I've got the VCC pin connected to 12VDC and the ground and VEE pins to ground. There is a ...
0
votes
2answers
137 views

Hysteresis not working properly

This question is related to my previous question about the battery charging and discharging. Here is the link to my previous question. I have made a small change in my previous schematic, which is ...
2
votes
2answers
179 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 ...
0
votes
2answers
483 views

Help with Piezo conditioning circuit schematic

I have the below schematic that uses a piezo sensor as input and relays that information to an Arduino board for processing. The schematic came from a few folks over at MIT that built a ping pong ...
2
votes
2answers
52 views

Flipping Output Logic

I have the following circuit: The diagram above has a pot between VCC, LM393 and Ground, on my board pictured below this is replaced by a voltage divider with two 10k pots. It looks like this: ...
-2
votes
3answers
205 views

A few OPAMP questions I have a hard time finding the answers to [closed]

I have a few questions, which, albeit, may seem pretty obvious to a lot of you, but I couldn't find the answers myself, so apologies in advance. Also, the pictures are pretty rough, I know, but that's ...
0
votes
0answers
50 views

BMS: Comparator using TLV1702

I was asked by my boss to develop a system to manage an automatic door battery system. The goal is for when, for example, the power goes out, you get home and want to open your garage door, with this ...
-1
votes
2answers
81 views

How to find exact low voltage and high voltage values?

How to find the Hysteresis comparator exact "V high and V low" values
0
votes
1answer
84 views

How to get the full Vcc output from comparator?

I am working on a circuit using a comparator for a school project, but in testing it is not acting as expected. Specifically, the output is not going all the way to the higher rail voltage attached ...
0
votes
2answers
101 views

Rail-To-Rail Comparator Design

I'm trying to detect small current pulses (~1.5mA). Currently I'm generating a ~20mV pulse on a sense resistor and feeding that to the input of an opAmp with some hysteresis. I'm having a bit of ...
1
vote
1answer
76 views

Comparator: What is appropriate for comparing ranges of about 50-100 mVs? Can I use an LM741 op amp?

I am attempting to create a high voltage signal when the voltage from a sensor I am using drops below a certain threshold, which will be between .05 and .1 Volts. I was trying to use an LM741 op amp ...
1
vote
3answers
230 views

How do you set the reference voltage for a comparator?

I know this is certainly a beginner's question but am a first year student so hopefully I can be forgiven. I was looking through a electronics booklet provided by IKES website, and it's talking about ...
0
votes
2answers
456 views

Solar cell powered supercapacitor charger with strange output voltage regulator problem

I have a strange problem in a low power circuit design. I designed a buck-boost converter as a maximum power point tracking circuit (control the output of solar cell within a small voltage range ...
3
votes
1answer
196 views

LM324 comparator IC getting burnt

I am using LM324N as a comparator which has Reference voltage of 1.2V to +ve terminal. It requires supply voltage VCC=24V & VEE=Gnd.When input is 0V Vout=24 and when input= above reference voltage ...
0
votes
2answers
51 views

Comparator won't flip to HIGH

I am learning to use a comparator (LM393N) and running into trouble. No matter what I do, the output is always LOW. I am running off of a 9V battery, and I've added a voltage divider to send half of ...
0
votes
1answer
58 views

LM393N with hysteresis and potentiometer

I am having a bit of a problem with this next circuit: The problem is, when there is 0V at the base of Q1 and when the potentiometer is set close to 100 kOhm. Because of the hysteresis set on LM393N, ...
2
votes
2answers
332 views

Maximum voltages of an op amp comparator

If I have an op amp setup as a comparator, e.g. like this one: I know that Vo represents the difference in the input voltages, but is there a maximum value these voltages can be? Is there a limit ...
1
vote
2answers
181 views

Detecting if one voltage is bigger than another without an operation amplifier (OP-AMP)

I can't get my hands on an OP-AMP chip right now so I'm wondering if there's any way to detect if one voltage is greater than another voltage without the use of an OP-AMP. I've heard differential ...
4
votes
2answers
169 views

Smallest Voltage that a comparator can detect

What is the smallest voltage a comparator can detect? Is it possible to set the reference voltage to a few millivolts, just above the noise margin for using a comparator circuit?
4
votes
2answers
387 views

Compare two voltages and output the lower of the two

I am working on a circuit that is connected to a 10V supply (can supply about 1-2mA). We have two signals, let's call them S1 and S2. We also have an input to the circuit called IN1. My goal here ...
3
votes
2answers
123 views

Checking whether two voltages are similar

I am pretty new to electronics so this may seem like a basic question, but how could I check whether two voltages are similar? For example, say I want to check whether | V1 - V2 | < 1.5V and output ...
1
vote
1answer
260 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 ...
2
votes
2answers
78 views

Use interrupt to determine a change in IR detector

I have build a schematic to read a counter. The counter has a white point at one of the digits, that I detect with a IR transmitter-receiver. The voltage at the receiver changes from 2.2 to 2.5 volts ...