How can I determine the input impedance of comparator

Hi Yee,

have a look at this simulation:

You can see, that there's no relevant voltage drop across the 100k resistor. So, the input of LM2903 is very high ohmic.

The Rin of comparator is dominated by C728. But the impedance of a 1nF cap only beomes relevant at very high frequencies. The impedance of a 1nF cap at 1kHz is 160kOhm and at 10kHz is 16kOhm.

yee.TSC

Kai

Yee
Since there has been no further question for a while, I am closing this post. If you have further questions, feel free to reply and the post will be re-opened.
Chuck

Thanks for your reply