422CHAPTER 9. PRACTICAL ANALOG SEMICONDUCTOR CIRCUITSputting a ESD bag on a grounded surface the same thing is accomplished. Faraday cages workby routing the electric charge around the contents and grounding them immediately. A carstruck by lightning is an extreme example of a Faraday cage.Static bags are by far the most common method of storing components and boards. Theyare made using extremely thin layers of metal, so thin as to be almost transparent. A bag witha hole, even small ones, or one that is not folded on top to seal the content from outside chargesis ineffective.Another method of protecting parts in storage is totes or tubes. In these cases the parts areput into conductive boxes, with a lid of the same material. This effectively forms a Faradaycage. A tube is meant for ICs and other devices with a lot of pins, and stores the parts in amolded conductive plastic tube that keeps the parts safe both mechanically and electrically.Figure 9.3:9.1.3ConclusionESD can be a minor unfelt event measuring a few volts, or a massive event presenting realdangers to operators. All ESD protections can be overwhelmed by circumstance, but this canbe circumvented by awareness of what it is and how to prevent it. Many projects have beenbuilt with no ESD protections at all and worked well. Given that protecting these projects is aminor inconvenience it is better to make the effort.Industry takes the problem very seriously, as both a potential life threatening issue and aquality issue. Someone who buys an expensive piece of electronics or high tech hardware is notgoing to be happy if they have to return it in 6 months. When a reputation is on the line it iseasier to do the right thing.9.2Power supply circuits – INCOMPLETEThere are three major kinds of power supplies: unregulated(also called brute force), linearregulated, and switching. A fourth type of power supply circuit called the ripple-regulated, is ahybrid between the ”brute force” and ”switching” designs, and merits a subsection to itself.