I am trying to build a high frequency (~ 5MHz) level shifter circuit. For this purpose, I designed a comparator circuit based on TI's THS3491.
The circuit schematic is shown below:
The D, D_bar voltage levels are 3.3V.
The circuit is working well until the ground of the square waveform generator and the power supply circuit is kept different. As soon as I connect both the grounds, high frequency signals gets pulled up to a digital 1 (24V), at lower frequencies, i.e. below 500KHz, I am still able to receive a waveform (though not perfect).
I am not able to figure out the reason for the same. Any help would be appreciated.