Kevin Weddle Posted April 26, 2005 Report Share Posted April 26, 2005 Perhaps the most overlooked by most enthusiasts is the RC time constant. The best way to determine if your circuit is good is to compare the time of the RC with the time of the signal. If the time of the signal is short, such a ramp of a square wave, the RC time looks very long to it. If the time of the signal is long, such as the DC of a square wave, the RC time looks very short to it.So, is it good to have a long RC or a short RC compared to the signal. Well a long RC of course. A long RC means that it takes a long time to charge or discharge.So what happens if the RC looks short compared to the time of the signal. Well a short RC means the charge and discharge time is short. If the 5RC is 1 second, it means the capacitor will charge completely to the applied voltage in 1 second. If the 5RC is 5 seconds, it will take 5 seconds to completely charge to the applied voltage. That being established, it is not difficult to see that when your signal goes DC, the signal time is long, the RC looks short, you get quick charge and discharge, and the voltage is indicated by the quickly charging and discharging capacitor. If the capacitor were not allowed to charge and discharge, the voltage would remain pretty much the same. Quote Link to comment Share on other sites More sharing options...
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