Comparator circuit with +/-5v saturates to +4v and -2v.

Papabravo

Joined Feb 24, 2006
19,284
Without looking at your schematic or knowing the type of comparator you are using; I can tell you the following

  1. Most comparators do not operate from rail-to-rail, so having a wider supply range is one solution.
  2. Some comparators have an open collector (open drain) output. You need to understand what that means
  3. Some comparators have an analog output, and you need to understand the implications for that choice.
 

BobaMosfet

Joined Jul 1, 2009
2,028
Comparator circuit with +/-5v saturates to +4v and -2v. How can I make this -2v at least -4v.
What you are describing sounds like it has more to do with what comparator IC you are using- which you also didn't tell us. Read the datasheet and UNDERSTAND it. We can't answer anything without more details.
 

Papabravo

Joined Feb 24, 2006
19,284
Provide a link to the datasheet for your comparator and perhaps some kind soul will guide you towards the information you seek.
 

Thread Starter

Shakespeare

Joined Sep 12, 2022
16
I am trying to use lm741 IC as a comparator.
+/- 10V is my supply to the rails. It's output saturation voltages are 9 and -7 Instead of 9 and -9. How do I fix this problem?

I know the lm741 is not a great IC but I want to use it.
 

BobTPH

Joined Jun 5, 2013
5,759
What are you using it for? Generally, we use a comparator to get a logic output, which is not usually bipolar.
 

dl324

Joined Mar 30, 2015
15,112
It's output saturation voltages are 9 and -7 Instead of 9 and -9. How do I fix this problem?

I know the lm741 is not a great IC but I want to use it.
You can't. LM741 can't swing that close to the rails. For lightly loaded outputs, guaranteed output voltage swing is 4V from the rails.
 

Papabravo

Joined Feb 24, 2006
19,284
I am trying to use lm741 IC as a comparator.
+/- 10V is my supply to the rails. It's output saturation voltages are 9 and -7 Instead of 9 and -9. How do I fix this problem?

I know the lm741 is not a great IC but I want to use it.
Can you find any justification from any source that suggests that what you want to do is even possible? You can try looking at a modern part if you want to get closer to the supply rails but getting all the way there may still be out of reach. The datasheet will tell how close to perfection you can get. Learn to read them instead of assuming you can do whatever you want.
 

Thread Starter

Shakespeare

Joined Sep 12, 2022
16
Can you find any justification from any source that suggests that what you want to do is even possible? You can try looking at a modern part if you want to get closer to the supply rails but getting all the way there may still be out of reach. The datasheet will tell how close to perfection you can get. Learn to read them instead of assuming you can do whatever you want.
Very bold of you to assume I'm ignorant.
I did read the datasheet and run tests on the IC. If you have nothing to say it won't hurt you to say nothing.
 

Papabravo

Joined Feb 24, 2006
19,284
Very bold of you to assume I'm ignorant.
I did read the datasheet and run tests on the IC. If you have nothing to say it won't hurt you to say nothing.
Ignorance was not my assumption at all. You asked a question that has an answer you don't want to hear. I'm assuming that you had some justification for your expectations, and I wanted to know what they were. I tried to offer some helpful suggestions to get you closer to your goal which you appear to have dismissed out of hand.

Copping an attitude when you don't get what you want is unlikely to produce the results you seek.
 

DickCappels

Joined Aug 21, 2008
9,317
Do you mind adding two transistors to your circuit? You can the saturation chactaristics you desire with an LM741 but it will need help from additional parts.
 

Papabravo

Joined Feb 24, 2006
19,284
Then you apparently didn't understand it, since nothing in there suggests the output would be ±9 volts with ±10V supplies.
So if that's not ignorance (lack of knowledge or information), then what do you call it?
Shocked Picachu face, that the world does not work according to a particular set of expectations.
 

Papabravo

Joined Feb 24, 2006
19,284
In his other thread he is using a 54 years old lousy LM741 opamp, not a comparator.
I suspect the threads are related because he is NOT getting the answer that he wants, and maybe he thinks asking the question differently will produce a different result. This is not an infrequent occurrence among those with double digit post counts.
 
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