Capacitor ripple and droop calculator

Constant discharge between ideal recharge events; ESR omitted.

circuits-capacitor-ripple.napkin / editable

SCENARIO COMPARISON

Compare the numbers.

This source describes an analytical model. Its quantities and checks are the view.

Scenario	rippleV
	2.12766
	1.70213

All calculated quantities are listed with the inputs. Switch to Source to inspect the equations.

SCENARIOS / CALCULATED VALUESSAME SOURCE

Change an input to see the consequences.

ripple budget2.13 V✓ passes

BASELINE INPUTS

current1 Afrequency100 Hzcapacitance4700 uF

CALCULATED

ripple2.1277 V

Edits change the baseline source.

THE SOURCE

Edits below update the same model.

# Capacitor ripple and droop
# Scope: Constant discharge between ideal recharge events; ESR omitted.
# Status: illustrative worked example; engineering review pending.
# Inputs are example values. Checks are editable example requirements, not standards.

current = 1 A
frequency = 100 Hz
capacitance = 4700 uF

ripple := current/(frequency*capacitance) [V]

check ripple budget: ripple <= 3 V

scenario alternative: current = 0.8 A

Calculated from your source · not saved

Baseline · Baseline

ripple budget2.13 V ✓ passes

alternative · alternative

ripple budget1.70 V ✓ passes

Illustrative first-order example. Checks are editable requirements, not design standards. The broader topic may require additional equations, data, and validation.

Formula and units

This example uses the following equations. Input names and units match the editable source above.

ripple: ripple = current/(frequency*capacitance) [V]

Original worked example

These are the baseline values in the downloadable source. Edits above let you test your own values.

Given

current: 1 A
frequency: 100 Hz
capacitance: 4700 uF

Calculated

ripple: 2.12766 V

Assumptions and limits

Constant discharge between ideal recharge events; ESR omitted.

The requirement checks use the limits written in this example. Passing a check does not establish that the model covers every load, material behavior, or operating condition in a real design.

Download this .napkin example ↓

Take it further with your agent

Napkin keeps the inputs, equations, checks and assumptions together in one study. Your agent sets it up; you change the numbers.

Try with Claude ↗

codex 'Use Napkin (https://napkin.engineering/mcp, or the local Napkin plugin) to build a study: Capacitor ripple and droop. Inputs: current waveform; capacitance; ESR; frequency. Outputs: voltage ripple; RMS current; ESR heating. Model scope: Ideal or parameterized lumped components. Read napkin_capabilities and the current snapshot. Ask me for the values that matter, label assumptions with units, author .napkin source, validate it and apply it with napkin_source using the current revision, then open the study. Add checks for the limits I supply. Keep unsupported analyses explicit.'

Claude needs the Napkin connector; Codex needs the Napkin plugin. Set up your agent ↗

The broader study

The topic brief below describes the broader scope. The worked example above states the particular calculation it implements.

Inputs: current waveform, capacitance, ESR, frequency
Outputs: voltage ripple, RMS current, ESR heating
Modes: calculate, compare, sweep
Drawing: Schematic and waveform

EXECUTABLE WORKED EXAMPLE · FIRST-ORDER MODEL · CHECK THE SCOPE & ASSUMPTIONS