
505
reservoir capacitor (Sec. 18.6) this defect is removed and at the same
time the average is brought nearly up to the peak voltage.
The conditions are not quite the same as in a detector, because the
current drawn is usually much larger and the frequency much lower.
Unless the reservoir capacitance is enormous, therefore, it has time
to discharge appreciably between one cycle and the next, as in Fig.
27.2c.
This is described as d.c. with a ripple, or unsmoothed d.c,
which would cause a hum if used to feed a receiver. The next
requirement, then, is a smoothing circuit, which is a low-pass filter
(Sec.
18.10) designed to impede the a.c. rippl ...