of discharge of the capacitor quickly reaches the rate of decrease of
the applied voltage causing the current and the negative output
voltage across R to level off at a low value.
d. At 60 usec, the applied voltage is equal to zero and Ec is
equal to ER. The capacitor continues to discharge at the same rate;
and after 61 usec, Ec is considered to be zero. The current and
output voltage are also zero at this time.
20.
LONGTIME CONSTANT.
a. When the time constant is long compared with the pulse rise,
duration, and decay times, the capacitor charges to only a small
fraction of the total applied voltage. Most of the applied voltage
appears across R, and the output waveform closely resembles the input
b. The pulse shown in Figure 34B is applied to the highpass RC
filter in Figure 34A. The time constant of the circuit is equal to
100 usec. Since the rise time of the pulse (10 usec) represents only
10 percent of 1 time constant, the capacitor charges only slightly,
and the resistor voltage closely follows the rise of the input pulse.
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