Page 48 - Op Amps Design, Applications, and Troubleshooting

Electrostatic Discharge 31

FIGURE 1.21 Wires that carry both digital and analog currents can intro-
duce noise to the analog circuits.

1.6 ELECTROSTATIC DISCHARGE

Anyone who has been in a cold, dry climate has probably walked across a carpet
or slid across a car seat and then witnessed a sizable high-voltage arc lumping
between his or her body and a nearby metal object. This discharge of static elec-
tricity is called electrostatic discharge or simply BSD, and can pose a serious threat
to op amps and other integrated electronic components. The sensitivity of an op
amp (or other component) to BSD is largely a function of the technology used to
build the device. In general, integrated circuits using MOSFET transistors are
more susceptible to damage by ESD than circuits employing bipolar transistors.
But, even bipolar circuits can be destroyed, or at least weakened, by ESD currents.
When handling integrated circuits—particularly in a cold, dry climate—you
should be sure that your body is not allowed to accumulate static charge. This can
be accomplished in several ways:

1. Attach a conductive strap to your wrist with the other end connected to a
ground potential. Many manufacturers offer straps of this type that provide
a discharge path for the static electricity, but do not present a safety hazard
to the wearer.
2. Always touch ground (e.g., a metal chassis) before contacting the integrated
circuit.
3. Condition the environment by either ionizing the air or using an effective
humidifier.