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comparator not comparing

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root2hell

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i dont understand why this comparator not going in saturation region, even i am using High speed comparator.
 

jiripolivka

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i dont understand why this comparator not going in saturation region, even i am using High speed comparator.

I can see that your comparator does function, only the output amplitude is lower than expected.
Overshoots indicate something wrong with the DC power supply. I would suggest to add DC to ground blocking capacitors to the DC power supply, and check signal source impedances. You can reduce comparator gain by a feedback resistor like in an opamp circuit, sometimes it helps.
 

THINKER_KAM_MAN

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I can see that your comparator does function, only the output amplitude is lower than expected.
Overshoots indicate something wrong with the DC power supply. I would suggest to add DC to ground blocking capacitors to the DC power supply, and check signal source impedances. You can reduce comparator gain by a feedback resistor like in an opamp circuit, sometimes it helps.

just a suggestion


reduce the pulse to 2V hight
the sine wave is 5VPK-PK it seems = 2.5v PK
therefore the PK value is all ways less than the pulse
 

root2hell

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still not getting expected output...
:(
and i dont know why i am getting inverted output.
comp_sche_op.JPGcomp_sche.JPG
 

FvM

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There are both general and specicfic circuit faults involved

Generally, don't AC-couple a signal to an OP, comparator, transistor etc. without DC bias. In this case, simply omit the series capacitor.

Specifically, LM319 can't work without a pull-up resistor because the output is open collector type. Review the datasheet!
 

godfreyl

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...i am using High speed comparator.
The LM319 needs a pull-up resistor at the outut. Try connecting the right side of R24 to +12V instead of ground.

edit - Oops, cross-post with FvM
 

Audioguru

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The output of this comparator and EVERY OTHER IC with an open collector output needs an output pullup resistor. A pullup is a resistor connected from its output to its positive supply voltage, not connected to ground as you have.
Then the output will be a squarewave and can be used for PWM.
 

root2hell

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Thanks FvM. Today i get to learn what Open collector type output mean very basic but what can i do if i was not knowing that . :p
 

Audioguru

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Why do you want an integrator?
If the comparator has a pullup output resistor then its output is PWM when it has the 50kHz sinewave and 500kHz triangle wave input signals in your first post.
An integrator is a lowpass filter which is slow. If you integrate the PWM output then you will have a signal the same as the 50kHz sinewave input.
 

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