A comparator compares two voltages or currents and switches an output to indicate which is larger.
-1
votes
2answers
119 views
threshold problem on a Schmitt trigger op amp
I have the Schmitt trigger op amp on the below diagram. (channel A & B refers the oscilloscope probes on the following figures).
The resistor values are selected to set the trigger threshold as ...
1
vote
1answer
69 views
connection from an comparator to an optocoupler
I have the circuit below to decode a signal that is defined as Logic high >9.5 V and Logic low <6 V
To determine the ...
-1
votes
1answer
109 views
non-inverting schmitt trigger op amp - replacing a zener diode on the input
I wonder if it is possible to replace the second figure below with the first one? Would both Vo output be the same on the figures below? If they are different, ...
-5
votes
0answers
44 views
Design a circuit that [closed]
compares two -4-bir binary numbers, A = A3A2A1A0 and B = B3B2B1B0, to check if they are equal. The circuit has one output E, so E = 1 if A = B and E = 0 otherwise.
Thx.
0
votes
1answer
63 views
Low power IR detector for microcontroller wake-up
I am working on an ultra low power infrared wake-up circuit for a microcontroller (Atmel XMEGA). I have IRDA comms working but the receiver uses too much current to keep on all the time. I need to run ...
1
vote
1answer
81 views
Magnitude comparator implementation
I have stuck on implementing magnitude comparator for 2-bit numbers (three functions - greater, equal, less).
It is pretty easy to implement it with AND and OR gates, but the point is the task is to ...
4
votes
3answers
142 views
Help understanding BJT voltage comparator
I'm trying to understand how a transistor voltage comparator works. For example I've been studying this LM339:
My questions are:
What are the current sources for and how would those actually be ...
1
vote
1answer
98 views
Problem with microphone powering up a comparator circuit
The circuit below is supposed to turn on a LED when the microphone input reaches these levels:
1V, 3V, 5V, 7V.
What this circuit does in real life is when we turn on the power, all 4 LEDs light up.
...
0
votes
1answer
65 views
newbie: comparator adjustable level shift
I'm trying to build a simple fpga logic analyser and wondering how to best design the input circuit.
I would like to support 8 channels, voltage between 0-5V, with a adjustable threshold range (lets ...
1
vote
3answers
240 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 < ...
7
votes
1answer
118 views
Issue with TI comparator
I'm having trouble with a comparator from TI (LMH7322). I use it in the circuit shown in the attached image "Comparator_1".
Outputs go to an FPGA. The circuit is supposed to take a single ended input ...
2
votes
2answers
237 views
Techniques for analyzing Comparator circuits?
I'm looking for some general guidelines/equations I can use to analyze circuits which use comparators. In particular, I'm interested in hysteresis.
For example, take the following open ...
1
vote
1answer
561 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 ...
0
votes
1answer
185 views
USB ground on MSP430 Launchpad interfering with Comparator_A input voltage
I'm trying to read an audio signal from an Android phone as a serial input to an MSP430G2553, adapting this design to use the MSP430's onboard comparator module instead of an LM324. The Android code ...
1
vote
1answer
182 views
Op-Amp Comparator precision voltage
I need to trigger a speaker if my input voltage is higher than 0.6 V, otherwise the speaker must not be triggered. That's the reason I'm using an AMPOP Comparator:
and, as far as I know, the ...
3
votes
1answer
143 views
Role of current source in comparator
I have this schematic of a quarter of the internals of an LM339 from this site
I want to know what the purpose of the four current sources are in this circuit, and how might they be implemented?
I ...
0
votes
3answers
115 views
Comparators Dragging Each Other Down
I've assembled a circuit which uses RC timing compared to the voltage across a potentiometer. It is intended to run the motor in this fashion:
...
9
votes
4answers
438 views
Lengthening a 5 ns pulse
I have a 5 ns pulse width High coming out of a comparator that is asynchronous. I am attempting to count this pulse. My current microcontroller (dsPIC33FJ) has an asynchronous counter on board, ...
4
votes
1answer
350 views
Single supply op-amps in series
I have 2 op-amps in series, one is configured as an inverting AC amplifier and one as a voltage comparator.
The purpose of this circuit is to detect a 4mV AC signal and trigger a transistor at the ...
0
votes
1answer
253 views
Use port for comparator and analog input?
I'm trying to use Port F on the PIC18F65J11 as both analog inputs and a comparator. For example, there are 7 pins on Port F, and I'd use 3 pins for comparator (2 comparator inputs, 1 comparator ...
7
votes
2answers
734 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 ...
2
votes
1answer
104 views
Does this setup create time distortion?
You have an RC element. After the RC element there is a comparator. After a given time of X minutes(X * 60 = R * C), the comparator reacts. Does voltage drop lead to time distortion, provided that ...
4
votes
2answers
458 views
Will this ADC circuit work as intended?
Here is revision 6 of the circuit. Hows it look? :)
(This is an ohmmeter circuit. It measures resistances from 1 to 10M ohm with an accuracy of 1%. The resistor (not shown) is measured between J5 and ...
2
votes
2answers
1k views
What is the difference between a general comparator and a differential comparator?
I notice that the LM339 quad comparator comes in 2 different varietys: general-purpose and differential. Besides a big difference in price, what is the difference between the two?
Specifically, I ...
4
votes
3answers
662 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 ...
4
votes
2answers
3k 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 12V DC system so I filled that in already).
I have a ...
2
votes
1answer
261 views
Are there op amps or comparators that run on >100V?
I was using two op amps with inputs crossed as seen here:
to make inverters for stepping up voltage with high efficiency. The design works well, but op amps seem to be only built for low voltages. I ...
1
vote
2answers
433 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
vote
3answers
1k views
Need help driving N FET gate from LM393 comparator output
I am working on a charge controller circuit idea I had. The circuit
'works' meaning it achieved desired output voltage but the fet doesn't
seem to be turning all the way on so lots of heat is ...
3
votes
2answers
701 views
How does this voltage comparator work?
Can somebody explain to me, how the following voltage comparator works?
I believe to recognise U4A as an inverting Schmitt trigger, but how everything fits together escapes me...
Should the ...
1
vote
5answers
449 views
Would this button trigger alarm circuit work?
This is a dead easy question for most of you! But I'm relatively new to circuit design, so I'd just like to ask whether this circuit might work (at all!)
Here's a picture of the circuit
...
2
votes
2answers
154 views
OPAMP has voltage on its supply when it shouldn't
I was trying to design a circuit after seeing this question. I know I used too much components than I should designing a circuit with this purpose. And sorry about the messiness of the schematic.
...
1
vote
1answer
2k views
Comparator using Logic Gates only
How might a comparator with only logic gates look like? Isit like:
3
votes
1answer
331 views
Help breadboarding a circuit?
I've been building a light based alarm system, using an LDR, Op Amp, AND gate, some resistors, and an output of buzzers..
Here's my circuit so far... It beeps when it senses light as well as being ...
1
vote
1answer
180 views
A device which will detect a difference in voltage
A comparator can compare two voltages and output a signal indicating whether one is greater than the other. However, for balancing a lithium-polymer battery pack, I need to measure the difference ...
1
vote
2answers
217 views
Connecting a high-speed comparator into a computer
I need to store the output of a stand alone comparator (Hittite HMC875LC3C) in computer RAM drive. Currently, I'm using an 8bit 2GHz ADC (an Agilent PCIe - Acquiris U1071A) to bridge between the ...
2
votes
4answers
570 views
Compare negative with positive, ignoring sign
I need to compare a negative voltage with a positive one, each on the order of a few hundred millivolts each; I want to compare the magnitudes, ignoring the signs, although only for this particular ...
4
votes
1answer
161 views
Comparator with two noninverting inputs?
On page 7 of the LTC3631 datasheet, the diagram shows a comparator with two noninverting inputs. What does such a comparator do?
2
votes
1answer
334 views
Common mode input voltage range and comparators on an MCU
The comparators on my MCU, a dsPIC33FJ128GP802, give the common-mode input range as AVdd-1.15V. AVdd is 3.3V, so does this mean the comparators can't compare voltages in the range of 2.15V to 3.3V?
0
votes
3answers
409 views
Comparator over I2C with programmable reference
I'm looking for a programmable comparator which has a digital or open-drain output and a voltage reference which can be programmed over I2C. My searches at my favourite sites of Microchip and Farnell ...
