3. Varistors

3.1 General

In theory, a varistor is an electrical component whose resistance varies with an imposed external parameter. In practice, varistors are only those components whose resistance varies as an inverse function of the applied voltage. Standards NF C 03-204 and IEC 617-4 define a varistor as an intrinsically variable, non-linear, voltage-dependent resistor with the symbol shown in figure 30 a. However, it is customary internationally to use the symbol shown in figure