32 votes

Why does this comparator not output a square wave?

You should realize that a 4.43 MHz square wave has a much larger bandwidth than 10 MHz. A "proper" 4.43 MHz square wave will contain frequencies up to and beyond 50 MHz. That is because a square wave ...
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30 votes
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Is there any reason as to why the schematic symbol of comparators is almost equivalent to that of op amps?

They are not completely different. They are much more similar than you think. Technically, a comparator is just an op-amp optimized to operate in the saturation region (have the output saturate ...
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29 votes
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Why do comparators generally have higher offset voltages than opamps?

High speed with a small difference is difficult to get. Note that not only do comparators tend to have higher input offset voltages than opamps, but also much higher effective noise, as to get high ...
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22 votes
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Can someone explain how this transistor comparator works?

The circuit is a comparator and can be remarkably useful more or less as shown. I have used a circuit essentially the same as that in production equipment to meet a requirement which was difficult to ...
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20 votes
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Why is there a short between my VCC and GND in this circuit?

You have fallen into a classic XY problem1 trap. However, thanks for briefly mentioning the original issue, as that makes the overall situation easier to understand. You have a genuine problem ("X"): ...
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16 votes
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What is the AVR's analog comparator speed?

The datasheet link you provided was for the shorter summary datasheet. You need to look at the complete datasheet to get the comparator propagation delay. http://www.atmel.com/Images/Atmel-42734-8-...
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What's the purpose of a diode to Vcc at an LM339 output?

When power supplies turn off, the diode discharges the capacitor, so it's empty when power supplies turn on again the next time. I am guessing that this is a power on delay timer, because it reads &...
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15 votes

Can a comparator (LM393) be used as an amplifier?

Take a look at the basic schematics of the internals shown in the data sheets for the LM324 (regular op-amp) and LM393 (comparator) respectively: - The input stages are both pretty similar but the ...
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15 votes

Is there any reason as to why the schematic symbol of comparators is almost equivalent to that of op amps?

A comparator is often close to being a linear amplifier that is optimised to achieve rapid switching around the point where the voltage difference between two inputs are very close to zero. A ...
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Can LM339 comparator inputs go way above Vcc?

"Absolute maximum ratings" are about not destroying the device. "Electrical characteristics" or "Recommended operating conditions" are about proper functionality. For example, a supply voltage of zero ...
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13 votes
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Negative feedback capacitor in Op-Amp comparator circuit

This is a typical use of a conventional Operational Amplifier working as a Comparator. Lets's first describe it intuitively: If we left C1 out of the circuit (disconnected), we have an Op-Amp with ...
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13 votes

Simplifying many window comparators

I think Brian's non-SW answer is the best but here's a purely analogue solution. Use a circuit that inherently chooses the highest voltage input (from several) and puts that to the output. Ditto the ...
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13 votes

Very high precision zero crossing detection

You'll likely want to measure the total of many zero crossings (and divide by 'many' before taking the reciprocal).. or average many measurements.. otherwise noise in the signal will unduly affect ...
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12 votes

Is there any reason as to why the schematic symbol of comparators is almost equivalent to that of op amps?

Both op-amps and comparators are types of amplifiers. The triangle symbol is used for these and many other kinds of amplifiers. You will find that power amplifiers and digital NOT gates also have very ...
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11 votes

Can a comparator (LM393) be used as an amplifier?

The LM393 modules you see advertised on eBay aren't microphone amplifiers as such. They are advertised as sound detection modules, which deliver a (more or less) digital ouput. That module has an ...
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11 votes
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Simplifying many window comparators

One window comparator, a 3 bit counter, and an 8:1 analog mux to connect one thermistor to the comparator. If all you need to know is that they are all fine; that's 3 chips, job done. (74HC163, ...
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11 votes
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How can there even be an input voltage on a long-tailed pair?

This is a classic misconception: "VBE is constant, BJT transistors are current-controlled devices." Nope, wrong. So, your #1 above is wrong. Long-tailed pairs are based on changes to VBE. The VBE ...
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11 votes
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Operational amplifier as a comparator at high frequency

The recommendations for you are very simple. Use a comparator for this application instead of an opamp. Select a newer part that operates with orders of magnitude faster response time. It would be ...
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10 votes
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LM358 (as comparator) output voltage less than supply voltage

LM358 is not a rail-to-rail output op-amp, so you should not expect it to produce an output near the positive supply voltage. Unfortunately, the datasheet doesn't go out of its way to make this ...
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10 votes
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Why does the comparator burn in this oscillator circuit?

Based on your layout and text description, the pinout does not match the datasheet. The positive and negative supply pins are swapped.
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9 votes
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Why do they usually make comparators open collector?

The main reason for using open-collector is so that several comparators can have their output connected together in a wired OR gate. All the open collectors can be tied together to a single resistor ...
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9 votes

Why do comparators generally have higher offset voltages than opamps?

Those op-amps with very low offset (such as the TLC2652) have much too low a bandwidth for what you want (about 2 MHz) so, realistically you need to compare apples with apples. Also, not specified in ...
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9 votes
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Voltage Comparator IC's Output (LM339) Never Goes To VCC (But Can Go To Ground)

The LM339, like a great many other comparators, has an open-collector output - the output is an NPN transistor with the emitter grounded and the collector connected ONLY to the output pin (see Fig. 1 ...
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9 votes

Saturation problem of comparator

When selecting a comparator, it is always best to choose a part that is specifically designed for the job. Op amps can be used as comparators, but really, it is usually best to just buy a comparator! ...
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9 votes

Flyback diode is acting weird

The LM311 has an open-collector output. You need to connect the open emitter to ground, not VCC, and provide a pullup resistor on the open collector output. Don't try to use an LED as a flyback diode....
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9 votes
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Window Comparator

There is no issue if the output is an open collector type. I found the text in the article you where referring to: As a result the output stage of the voltage comparator is generally configured ...
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9 votes
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Why is the output not zero for zero differential input?

In an ideal world, your circuit would indeed not put out any differential voltage between points X and Y because it is fully symmetrical. There are no random offsets in SPICE, it does exactly what you ...
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8 votes
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Why does my comparator not give an output?

An LM339 needs a pull-up resistor on the output or you'll just get diddly-squat ZERO out of it.
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8 votes
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Controlling heater with PWM through MOSFET

It's probably not mostly from the inductance. More likely, pulling close to 8 Amps from the battery has a significant effect on the battery voltage, and this changes the switching thresholds around ...
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