Dear Anush,

Welcome,

Since your multiplexer is a transmission gate type, it inserts an effective resistance in the path of the signal to the comparator. If the input impedance of the comparator is relatively low, then the resistive divider network will be upset due to this loading.

There are two solutions;

You have to increase the input impedance of the comparator while decreasing the divider resistances.

or you add abuffer at the input of the comparator or even you can buffer the divider from the multiplexer by buffer amplifier.

Best wishes 

Hi,

The CMOS TG is NOT an ideal switch.In the ON state  TG exhibits a resistance - several kohms. So, you have designed more complicated resistor divider than you intended ;-)

The solution is very simple. Instead of  CMOS TG use so  called clocked inverter to  build your MUX. Like this one :

https://www.researchgate.net/figure/251832949_fig3_Figure-3-Current-waveforms-comparison-of-CDFF-and-proposed-MSDFF

Regards,

Zekry sir and jawaorski sir

Thank u so much for the replies

Let me try this technique