Phase shift a square wave
took a crack at it. this isn't it, goes from 0 to less than 90 deg shift.
principle along the lines of @hacktastical's comment.
pot makes two symmetrical control currents, and diode bridge steers, steering controlled by input clock. output of steered current bridge makes variable slope ramps out of the input clock's rising and falling edges. then comparator vs mid supply produces output.

falstad original here ... note &quot;resistance&quot; slider on the right that controls the pot. changes take a few cycles to settle (in case it is not ramping rail to rail, because of action of the 20k resistor to center it. but at that point the phase shift is maxed out anyway)