When making analog op-amp or 555 timers, many times RC time constant is employed. Lets say we want 1 sec time constant: We could chose for instance the combination R=100k and C=10uF. Or we could choose R=100Meg and C=10nF. We have zillions of possibilities here.
If possible I was always choosing the combination such that I can avoid using electrolytic capacitor type. For example in my last circuit, to obtain a 10 sec RC time constant I used R=1Meg C=10uF. I would like to use nF level capacitors to avoid using electrolytic capacitor. But in this case then I have to increase R to very high resistances.
Here my question is:
1-) Is keeping the cap value low in nF level and increasing the R to hundreds of mega-ohms problematic? I thought we might be avoiding the use of electrolytic capacitor but then the very high resistor value could introduce more error?
2-) If I keep the resistor in kOhm level I should use then uF level cap. In this case what is the best alternative to electrolytic caps in uF level to obtain better accuracy and repeatability.
edit: Capacitors I use should not be surface mount.