ECEN 1400 - Introduction to Digital and Analog Electronics

Peter Mathys, Spring 2014


Capacitors

The figure below shows the schematic symbols for regular capacitors (left) and electrolytic capacitors (right). Note that electrolytic capacitors are polarized. Applying a dc voltage in reverse will damage and eventually destroy them. Regular capacitors are generally used for signal processing and high frequency applications. Electrolytic capacitors are mostly used for short term energy storage in power supplies or for low frequency audio applications. Capacitance is measured in farad (picofarad, microfarad, etc.). In addition, capacitors are also characterized by the maximum voltage that can be applied across the terminals without permanent damage.

Symbols for Capacitor and Electrolytic Capacitor

Capacitors are made from many different materials and come in a wide variety of styles. A small sample of real capacitors is shown in the photograph below (click to enlarge). Some capacitors use the same color code as the resistors. An example is the 4th capacitor from the left. The three capacitors on the right are electrolytic capacitors.

Different Examples of Capacitors

The capacitors that you have in your lab kit are shown in the next picture (click to enlarge).

Capacitors in the Lab Kit

The six capacitors on the left are regular ceramic capacitors which use a ceramic material as dielectric between the two plates of the capacitor. These capacitors are labeled with their capacitance in pF in the same way as the resistor corde works. For example, 102 stands for 10x102 = 1000 pF = 1 nF. The five capacitors on the right are electrolytic capacitors in the range from 1 uF to 470 uF with voltage ranges from 35 V to 50 V. Be sure to observe the polarity when using these capacitors. Reverse polarity will destroy them.