2-13Figure 2-5.—Warning symbols for ESDS devices.You commonly experience static build-up during the winter months when you walk across a vinyl orcarpeted floor. (Synthetics, especially plastics, are excellent generators of static electricity.) If you thentouch a doorknob or any other conductor, an electrical arc to ground may result, and you may receive aslight shock. For you to experience such a shock, the electrostatic potential created must be 3,500 to 4,000volts. Lesser voltages, although present and similarly discharged, normally are not apparent to yournervous 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 HUMIDITYITEMLOW (10 - 20%)HIGH (65 - 90%)WALKING ACROSS CARPET35,000V1,500VWALKING OVER VINYL FLOOR12,000V250VWORKER AT BENCH6,000V100VVINYL ENVELOPES FOR WORK INSTRUCT.7,000V600VPOLY BAG PICKED UP FROM BENCH20,000V1,200VWORK CHAIR PADDED WITH URETHANE FORM18,000 V1,500 VQ-10.At approximately what minimum voltage potential should you be able to feel an electrostaticdischarge?Metal oxide semiconductor (MOS) devices are the most susceptible to damage from ESD. Forexample, an MOS field-effect transistor (MOSFET) can be damaged by a static voltage potential of aslittle as 35 volts. Commonly used discrete bipolar transistors and diodes (often used in ESD-protectivecircuits), although less susceptible to ESD, can be damaged by voltage potentials of less than 3,000electrostatic volts. Damage does not always result in sudden device failure but sometimes results indevice degradation and early failure. Table 2-1 clearly shows that electrostatic voltages well in excess of
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