Analog and Op-Amps
Model class: Standard approximation
Peak detector and hold-time designer
Estimate peak-detector droop from hold capacitance, total leakage current, and hold time.
Interactive engine
Start with the stated conditions.
Values stay in this browser. Choose a representative scenario, then calculate deliberately.
Example ready
Calculate to inspect the result.
The result will identify the direct answer, assumptions, and any warning that changes the next decision.
How much does each input matter?
Each row holds every other input fixed at its current value and moves one input by ±10%, using the same model as the main result. It identifies which input is the binding lever, not a full tolerance stack.
Assumptions to check
- The entered peak-detector values represent the stated operating condition.
- This standard approximation is evaluated in the declared lumped or first-pass model.
- A peak-detector calculation is not a component qualification or safety approval.
What this peak-detector calculation establishes
Estimate peak-detector droop from hold capacitance, total leakage current, and hold time. The useful result is the stated electrical quantity and the decision it supports, not an unstated claim about a finished product. This engine keeps the governing relationship visible so an input, unit, condition, or model boundary can be reviewed before a value becomes a component or layout choice.
Constant-current droop equals total leakage current times hold time, divided by hold capacitance. Treat the number as a first-pass result for the declared operating point. When a source, load, temperature, frequency, waveform, component tolerance, or measurement condition changes, repeat the calculation at the relevant corner rather than assuming the nominal answer persists.
Worked decision context
A 1 µF hold capacitor with 1 µA total leakage droops 10 mV in 10 ms under the constant-current approximation. That example verifies the equation and illustrates the scale of the result, but it does not select a part by itself. Compare the result with available values, ratings, tolerance bands, and the receiving circuit or physical environment before implementation.
Use the primary output to identify the binding constraint. If it leaves little margin, document which input dominates and use selected-part data, a higher-fidelity model, simulation, or measurement. This is especially important when a small numerical difference changes a thermal, timing, noise, or reliability decision.
Limits and validation handoff
It omits diode and switch leakage variation, following-stage bias current, dielectric absorption, and acquisition-time tradeoffs. The calculation does not silently include omitted parasitics, installation conditions, manufacturing variation, or product policy. Those conditions can be decisive even when the arithmetic is exact for the selected model.
Record inputs, units, model assumptions, and the intended decision with the result. Verify the leading risk against the selected component data sheet and a representative measurement when the circuit has consequential energy, high voltage, safety, compliance, or reliability requirements.
Common mistakes
- Treating the peak-detector result as a guaranteed operating limit rather than a first-pass standard approximation estimate.
- Mixing a data-sheet value measured under one condition with this peak-detector calculation performed at another.
- Selecting a component before checking the boundary this calculation names: it omits diode and switch leakage variation, following-stage bias current, dielectric absorption, and acquisition-time tradeoffs.
Model limit and handoff
Keep the entered peak-detector conditions with the calculation, then validate the binding limit using the selected component, physical implementation, and representative operating corner.
FAQs
Is this peak-detector result sufficient to approve a design?
No. It applies standard approximation reasoning to the entered peak-detector values and names the checks that still need selected-part data, a higher-fidelity model, or measurement. It omits diode and switch leakage variation, following-stage bias current, dielectric absorption, and acquisition-time tradeoffs.
What does this peak-detector calculator assume that could make the result wrong?
Constant-current droop equals total leakage current times hold time, divided by hold capacitance. If the entered values do not match the real operating condition, the result no longer describes the actual circuit.
Where should this peak-detector result go next?
Compare this peak-detector result with Building an analog error budget, then use the stated next decision below the calculator to move from this first-pass number toward an implementation.