18 th Dec 2004 Capacitors Application Edward Chen

18 th Dec 2004 Electrode Plates Dielectric The value of a capacitor is measured in farads. For 1 farad of capacitance, 1 coulomb of charge is stored on the plates, when 1 volt of force is applied. 1 farad = 1 coulomb / 1 volt 1 coulomb represents ~ 6 x electrons All capacitors utilize the same basic mechanism in their structure 2

18 th Dec 2004 ESL - Inductive Reactance (X L ) opposes Capacitive Reactance X Z ESR XCXC X L X 0 Impedance is now a factor of resultant Z = (X C -X L ) + ESR 2 2 3

18 th Dec

Self-Resonance Reactance Frequency X C decreasing The frequency at which X C = X L is the self-resonant frequency. At this frequency, X C =-X L, or zero, and the impedance is equal to the ESR. Prior to this frequency, component behaves as capacitor; after this frequency, component behaves as inductor. X L increasing self-resonant frequency. 5

18 th Dec 2004 Capacitor Application Decoupling Coupling Filtering Timing/Wave-shaping

18 th Dec 2004 Decoupling Power Supply Load (ex.IC) VinVout Vin Vout Function: Absorb the voltage change (noise). Suitable Cap: Tan Cap, KO Cap, MLCC, Al E Cap

18 th Dec 2004 Coupling Function: Remove the DC voltage of A circuit and Transmit the exchange voltage to B circuit. (Allow an AC signal pass, but stop DC.) Suitable Capacitors: Tan Cap, MLCC Ex. Horn.

18 th Dec 2004 Filtering Function: Rectified AC smoothing Frequency selective filtering Suitable Cap: KO, Tan Cap, Hi C/V MLCC, Al E Cap

18 th Dec 2004 Timing / Wave-shaping Function: Timer Circuit (RC Timer). Suitable Cap: MLCC, KO Cap.