it is so clear that a resistor never produces phase shift in signal and it's value is independent from the frequency unless special resistors like those in switched capacitor circuits that are freq dependent and not a real resistor but some switched caps that play the resistor role.
I meant what impedance would produce a phase shift of 90 degrees. So basically what I'm asking is what value of capacitor should i use. (sorry i didn't mention this before)
any value of capacitor can do that by it self only if we have just capacitor in our circuit but if the cap and res utilized together they never can produce precisely 90 ph.sh and if we have cap and inductor with together they also can do that unless their impedances be equal to each other.
