Direct Energy, 2018a

2 CAPACITORS AND PIEZOELECTRIC DEVICES 29
Figure 2.2: Range of capacitance andmaximum voltage values for various
capacitor types, following [21] and[22].
be damagedif it is placedin a circuit where the voltage across it exceeds
the maximum ratedvalue. Approximate ranges for these parameters for
capacitors with dierent dielectric materials are shown in Fig. 2.2. Capacitance
ranges are on the vertical axis, andmaximum voltage ranges are on
the horizontal axis. For example, electrolytic capacitors often can be found
with capacitance values ranging from 10 −7 to 1 F andmaximum voltage
ratings in the range of 1 to 1000 V. Similarly, ceramic capacitors can often
be foundwith capacitance values ranging from 10 −13 to 5 · 10 −4 F and
maximum voltage ratings in the range of 1 to 50,000 V.
While capacitance andmaximum voltage rating are important parameters
to consider, they are not the only considerations. Another factor to
consider is temperature stability. Ideally, the capacitance will be independent
of temperature. However, all materials have a nonzero temperature
coecient. Ceramic andelectrolytic capacitors tendto be more sensitive to
temperature variation than polymer or vacuum capacitors [22]. Accuracy,
or precision, is also important. Just as resistors are labeledwith tolerances,
capacitors may have tolerances of, for example, ±5% or ±10%. Another
factor to consider is equivalent series resistance [23, ch. 1]. All materials
have some resistivity, so all capacitors have some nite resistance. To
account for the internal resistance, we can model any physical capacitor