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I just went to Google and typed in --- without quotes around it ---

charge capacitor analog wave

One thing that differentiates analog from the digital is that capacitors take time to charge and discharge current to produce a desired waveform whereas a digital signal can produce a perfect waveform. Analog methods always have a bit of a bump or a curve while the circuitry charges and discharges.

Here's some of the better examples I found during the search.
The bottom link is really cool. Be sure to check out the triangle and sine wave circuitry, too.

http://www.allaboutcircuits.com/ --- all about circuits, electronics, etc.

http://users.telenet.be/educypedia/e...javaanalog.htm -- interactive

http://www.greenandwhite.net/~chbut/rc_cir.htm -- good example

http://www.play-hookey.com/analog/sq...generator.html --- shows circuitry required to make a square wave.