Table 2-1.—Typical Measured Static Charges (in volts)

2-13 Figure 2-5.—Warning symbols for ESDS devices. You commonly experience static build-up during the winter months when you walk across a vinyl or carpeted floor. (Synthetics, especially plastics, are excellent generators of static electricity.) If you then touch a doorknob or any other conductor, an electrical arc to ground may result, and you may receive a slight shock. For you to experience such a shock, the electrostatic potential created must be 3,500 to 4,000 volts. Lesser voltages, although present and similarly discharged, normally are not apparent to your nervous system. Some typical measured static charges caused by various actions are shown in table 2-1. Table 2-1.—Typical Measured Static Charges (in volts) RELATIVE HUMIDITY ITEM LOW (10 - 20%) HIGH (65 - 90%) WALKING ACROSS CARPET 35,000V 1,500V WALKING OVER VINYL FLOOR 12,000V 250V WORKER AT BENCH 6,000V 100V VINYL ENVELOPES FOR WORK INSTRUCT. 7,000V 600V POLY BAG PICKED UP FROM BENCH 20,000V 1,200V WORK CHAIR PADDED WITH URETHANE FORM 18,000 V 1,500 V Q-10. At approximately what minimum voltage potential should you be able to feel an electrostatic discharge? Metal oxide semiconductor (MOS) devices are the most susceptible to damage from ESD. For example, an MOS field-effect transistor (MOSFET) can be damaged by a static voltage potential of as little as 35 volts. Commonly used discrete bipolar transistors and diodes (often used in ESD-protective circuits), although less susceptible to ESD, can be damaged by voltage potentials of less than 3,000 electrostatic volts. Damage does not always result in sudden device failure but sometimes results in device degradation and early failure. Table 2-1 clearly shows that electrostatic voltages well in excess of