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Schmitt trigger detection problem

I am using Phillips LPC760 emulator(5V power supply) for Schmitt based sine detection.
There are two problems:

1) The Schmitt trigger output should follow the following rule as per the LPC760 datasheet:
Vil(Negative going threshold) = -0.5V to 1.5V
Vhl(Positive going threshold) = 3.5V to 5.5V.
However the Schmitt output doesn't follow the above rule at all. The positive going threshold is 2.76V and negative going is 1.64V when input sine signal is 2.44V p-p and 1.6V positive DC shift.

2) The Schmitt trigger levels should not change when input signal changes its p-p amplitude. However, When the input signal peak-peak amplitude changes, so does the Schmitt trigger levels. This is not explained.

Please let me know the solutions to these.








is not following the When i throw the Schmitt detector output for detecting Schmitt

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