Table of Contents
Parallel Capacitors
When capacitors are connected in parallel, their capacitances add together to give the total capacitance. This is because each capacitor independently stores charge from the same voltage source. The total charge stored is the sum of charges on all capacitors, and since Q = CV, the total capacitance is the sum of individual capacitances.
Parallel capacitors are used to increase total capacitance, reduce equivalent series resistance (ESR), improve frequency response, and provide bulk energy storage. In power supply decoupling, multiple small capacitors in parallel are preferred over one large capacitor for better high-frequency performance.
Formula
Series vs Parallel Comparison
| Property | Parallel | Series |
|---|---|---|
| Total C | Sum of all C | Less than smallest C |
| Voltage | Same across all | Divides across each |
| Charge | Divides among caps | Same on all caps |
| Use case | Increase capacitance | Increase voltage rating |
Frequently Asked Questions
What is the voltage rating of parallel capacitors?
The voltage rating of parallel capacitors is the LOWEST rating among them. Since they all see the same voltage, the weakest link determines the maximum safe voltage. Always use capacitors with the same or higher voltage rating than your supply.
Why use multiple small capacitors instead of one large one?
Multiple smaller capacitors in parallel have lower total ESR and ESL (parasitic inductance), giving better high-frequency decoupling performance. This is why PCB designs place several 0.1µF capacitors near ICs rather than one large electrolytic capacitor far away.