Pittsburgh Business Daily

How to calculate capacitor values in integrator and differentiator circuits?

If I'm replacing the resistor with 1K, 10K, and 100K resistors then how do I calculate the capacitor values for a time constant value tau = 1ns? What about for differentiator circuits? Is it the same thing?

Public Comments

1. T = RC = 1ns = 1x10^-9 s for R = 1Kohm = 1x10³ ohm C = T/R = 10^-9/10³ = 10^-12 F for R = 10 Kohm = 1x10^4 ohm C = T/R = 10^-9/10^4 = 10^-13 F Similarly, for R = 100 kohm
2. Time constant is tau=RC, so C = Tau/R (s/ohm), but your gain would depend on the resistance you choose.
3. time constant = RC An integrator with a 1 nS time constant is a bit unusual. 1 ns = 1k* C C = 1 pf 1 ns = 10k* C C = 0.1 pf .
4. I am not sure you are asking you question right. A time constant of 1 nanosecond implies you are talking about frequencies in the100's Megahertz range. As you have seen the capacitor values are 1 picofarad, 0.1 picofarad, and 0.01 picofarad. I have never seen capacitors so small. Needless to say with these extremely small capacitance, capacitor lead length will add an appreciably amount to the capacitance.