The LM, LM, and LM devices are single high-speed voltage comparators. High-Reliability Automotive Applications; Configuration Control and Print. NOTE: Page numbers for previous revisions may differ from page numbers in .. A typical LMMIL application compares a single signal to a. Circuit Description. FIGURE 1. Simplified Schematic of the Comparator. National Semiconductor. Application Note Robert J. Widlar. October

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For a better experience, please enable JavaScript in your browser before proceeding. Problem with LM voltage comparator. Thread starter Strablan Start date Dec 16, Strablan New Member Dec 16, Dear all Can’t get an LM applicafion to work as it appears it should – probably something obvious but due to ignorance on my part but I cant see it.


Have hooked it up as follows: Cant get pin 7 to turn on though. Is there something obvious about this chip that I am not aware of that would be the problem? Many thanks for any help:? Comparator output Like many comparators, the LM has an open collector output.

Did you tie a pullup resistor try 10K to VCC on pin 7? Strablan New Member Dec 18, I have attached a diagram of what I am trying to do, hopefully you will be able to see where I am going wrong Again, many thanks.

LM output Your problem is that the LM has an open loop gain of approx. This means that the output will swing to one or the other supply rails with a miniscule input level approx.

In your case because of the resistor in the line for pin 3 it goes high turning of the LED. You need to reduce the gain of the circuit using Feedback.

Problem with LM311 voltage comparator

Have a look at any textbook on negative feedback or search the web. Hope this helps Sandyw. Note that many of the circuits in the app. Here are some other links for more info: Strablan New Member Dec 19, Please excuse my ignorance but I really am a complete newbie on all of this.


Just checking I understand your comments applicatkon, Does the voltage for the reference input pin pin 2 or 3 need to be approximately half that supplied to pin 8? And that the 47k resistor by led needs to be replaced by one of approx ohms? Thanks for your patience.

Does the voltage for the reference input pin pin 2 or 3 need to be approximately half that supplied to pin 8? Strablan New Applicatioh Dec 24, You must log in or register to reply here.

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