Practical Capacitor Tolerance Selection for Coupling, DC Blocking and Bypass Applications

Proper selection of suitable capacitor tolerances is governed to a great extent by the type of application under consideration. This point should always be taken into account when designing for the best balance between cost and performance. For example, DC blocking, coupling and bypassing applications are not very sensitive to the variations in capacitor value that are due to the choice of widespread tolerances. In contrast, applications such as filtering and matching will usually require narrow spread capacitance tolerances in order to meet the specific demands of those designs.

This discussion will examine the impact of capacitor tolerance on overall circuit performance and will focus on DC blocking, coupling and bypassing applications. Pertinent electrical parameters such as the equivalent series resistance (ESR), series resonant frequency (FSR),
magnitude of the impedance (ZC), capacitor RF current (IC), power dissipated by the capacitor (PCD) and reflection coefficient (ρ) will be considered.