> A diode blocks AC and allows DC to pass.  By using the 
> correct combination of diodes you can convert an AC current 
> into a DC current.  (Pages 45-46 of The Art of Electronics, 
> 2nd Ed., Page 47 of Forrest Mimms' Getting Started in 
> Electronics.)  This diode circuit is called a full-wave 
> rectifier.  The output of this looks like a bunch of speed 
> bumps next to each other.  Forrest calls this a "pulsating 
> voltage" (page 36) while Horowitz & Hill call it a "ripple" 
> (Page 46).  

Each is correct from the authors point of view. Ripple is the word most
often used when people are talking about power supplies or other
applications where the desired voltage does not change. Pulsating is just a
general (and pretty accurate) description of that wave. 


> How to fix this?  This gets confusing.  Forrest Mimms shows 
> on page 36 that a capacitor connected to + and - will smooth 
> out (filter) the output voltage.  But on page 45 of The Art, 
> Figure 1.72, they show a resistor on the + side with the 
> capacitor crossing + and -.  However on page 37, Mimms calls 
> this particular RC circuit an Integrator which would turn a 
> square wave into a sawtooth wave.

The resistor helps to "disconnect" the capacitor, and therefore the output
of the circuit, from the input. It allows the capacitor to have more effect
with a smaller farad rating. 

Again, the terms are correct from the authors point of view. A ripple filter
is an integrator. Hopefully, the output is integrated so much that it
approaches DC. With the right components, the sawtooth will be almost flat.
With other components, the sawtooth will reach almost the full range of the
square wave.

In each case, the VALUES of the components in the circuit probably mean as
much as the connections of the components. An integrator will have a larger
resistor and a smaller capacitor for less integration. A ripple filter will
have a much smaller resistor (probably none aka a resistor of 0 ohms) and a
larger capacitor for more integration.

Hope that helps.

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