caps are 1)everywhere due to parasitic structures and 2)added specifically (along with their parasitics) to add filtering functions. To understand where to place and how large is the function of design. This will be a major function in your future work. Enjoy.

This is an all encompassing question. Capacitors impede the flow of AC according to capacitance value, and are ideally transparent at DC. There are several major applications:1. Power supply bypassing: All leadwires exhibit inductance. Capacitors at the power pins provide low impedance for integrated circuit operation, offsetting the "floppy" power characteristics of leadwire distance from the power supply. Used in that way, capacitors are almost like a short term battery. 2. Frequency compensation: The reactance (or tendency to impede flow of AC) increases with frequency. So if you were to build an audio amplifier for example, you would use a series resistor with a capacitor to ground to roll off treble, and a series capacitor with a resistor to ground to roll off bass.3. Capacitors are used for interstage coupling in AC amplifiers, again like those for audio. They block DC, but conduct AC. The higher the microfarad value, the lower the frequency which can be transferred. This is a thumbnail view of what capacitors do. There are many other applications and purposes which cannot be covered in just a few minutes. You can consider a capacitor like an electronic equivalent of a mechanical dashpot, if you are familiar with the concept. One of the best references is the ARRL Amateur Radio Handbook, a library item. But you really need to experiment on your own to learn the rudiments of circuit design, and to get an intuitive feel for what components do. Hope this helps.Bernie Katz. www.technicaldevelop.com<a href="http://www.technicaldevelop.com">Technical Develop</a>