A Problem about LM2903

[KAKU]

Regarding the problem of different simulation results when the non-inverting input terminal and the inverting input terminal of the comparator LM2903 are different, as shown in the figure. And why can't the input be negative when it is powered by a single power supply?



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[Harald Kapp]

Regarding the problem of different simulation results when the non-inverting input terminal and the inverting input terminal of the comparator LM2903 are different, as shown in the figure.

Where's the question? What are the different results that you are worried about? What do you expect, what do you see instead?

And why can't the input be negative when it is powered by a single power supply?

The internal circuit of the LM2903 looks like this:

When you apply a negative input voltage to IN+ or IN-, the base-collector diodes (marked red) will become conductive and clamp the input to GND.

 

[KAKU]

Where's the question? What are the different results that you are worried about? What do you expect, what do you see instead?

The internal circuit of the LM2903 looks like this:
View attachment 52872
When you apply a negative input voltage to IN+ or IN-, the base-collector diodes (marked red) will become conductive and clamp the input to GND.

Sorry.
Maybe I do not express my question clearly.
My problem is why the simulation results are different when the non-inverting input terminal and the inverting input terminal of the comparator LM2903 are different.

 

[Harald Kapp]

why the simulation results are different

Different from what?
Please state clearly what your inputs to the comparator are, which output you expect and which output you get instead of the expected.

 

[Audioguru]

Your 15V RMS input voltage has peak voltages of +21.2V and -21.2V which are destroying the comparator's input that must be within the power supply voltage which is +15V and 0V.
Therefore you must attenuate the input voltages.