Zener shunt-regulator screening calculator

Shunt regulator at supplied zener voltage; ideal clamp.

circuits-zener.napkin / editable

SCENARIO COMPARISON

Compare the numbers.

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

Scenario	seriesCurrentA	zenerCurrentA	zenerPowerW
	0.0209091	0.0109091	0.0556364
	0.0136364	0.00363636	0.0185455

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.

regulation current positive0.01 A✓ passes

BASELINE INPUTS

supply12 Vzener5.1 VseriesResistance330 ohmload10 mA

CALCULATED

seriesCurrent0.020909 A

zenerCurrent0.010909 A

zenerPower0.055636 W

Edits change the baseline source.

THE SOURCE

Edits below update the same model.

# Zener shunt-regulator screening
# Scope: Shunt regulator at supplied zener voltage; ideal clamp.
# Status: illustrative worked example; engineering review pending.
# Inputs are example values. Checks are editable example requirements, not standards.

supply = 12 V
zener = 5.1 V
seriesResistance = 330 ohm
load = 10 mA

seriesCurrent := (supply-zener)/seriesResistance [A]
zenerCurrent := seriesCurrent-load [A]
zenerPower := zener*zenerCurrent [W]

check regulation current positive: zenerCurrent > 0 A

scenario alternative: supply = 9.6 V

Calculated from your source · not saved

Baseline · Baseline

regulation current positive0.01 A ✓ passes

alternative · alternative

regulation current positive0.00 A ✓ 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.

series current: seriesCurrent = (supply-zener)/seriesResistance [A]
zener current: zenerCurrent = seriesCurrent-load [A]
zener power: zenerPower = zener*zenerCurrent [W]

Original worked example

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

Given

supply: 12 V
zener: 5.1 V
series resistance: 330 ohm
load: 10 mA

Calculated

series current: 0.0209091 A
zener current: 0.0109091 A
zener power: 0.0556364 W

Assumptions and limits

Shunt regulator at supplied zener voltage; ideal clamp.

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: Zener shunt-regulator screening. Inputs: input range; load; zener voltage/current bounds. Outputs: series resistor; zener and resistor dissipation. 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: input range, load, zener voltage/current bounds
Outputs: series resistor, zener and resistor dissipation
Modes: calculate, compare, sweep
Drawing: Schematic and waveform

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