4-14
Figure 4-10B.—Capacitor filter. SLOW DISCHARGE
From your earlier studies in basic electricity, you may remember that one time constant is defined as
the time it takes a capacitor to charge to 63.2 percent of the applied voltage or to discharge to 36.8 percent
of its total charge. This action can be expressed by the following equation:
t = RC
Where: R represents the resistance of the charge or discharge path
And:
C represents the capacitance of the capacitor.
You should also recall that a capacitor is considered fully charged after five RC time constants. Refer
to figure 4-11. You can see that a steady dc output voltage is obtained when the capacitor charges rapidly
and discharges as slowly as possible.
