Wolfram|Alpha Tips

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tip #8. RC low pass filter step response

The famous RC low pass filter response can be easily computed, as a solution of the following differential equation :

solve x'+x = Heavyside

Please note that the Heavyside function refers to the unit step function, and that the time constant is 1s in this example.

tip #7. Open Loop Integrator : why not ?

Just looh at the unit step response !

transfer function 1/s

tip #1. Cutoff frequency of a first order low pass filter

How to find the right value for the capacitor used in a low pass filter having a cutoff frequency of fc=1/(2pi.R1.C) where resistor R1 and frequency fc values are known ?

use solve ( 1/(2.pi.r1.C.1e-9) = fc) with r1=1100, fc=24000.

NB: don't forget the 1E-9 factor in order to get the result in nanofarads.