calculate_effective_capacitance
Effective capacitance of a Class II MLCC at real operating conditions — the marked value is not the value in circuit. Multiplies the four loss mechanisms that compound: DC bias (the dominant one, typically 35-65% loss at rated voltage and…
Instructions
Effective capacitance of a Class II MLCC at real operating conditions — the marked value is not the value in circuit. Multiplies the four loss mechanisms that compound: DC bias (the dominant one, typically 35-65% loss at rated voltage and worse in small cases), AC signal level, temperature coefficient, and logarithmic dielectric ageing, then applies the part tolerance. Returns the full factor stack so you can see which mechanism hurt most. Class I (C0G/NP0) parts correctly short-circuit to tolerance-only. Pass measured_retention_at_bias from a datasheet curve (Murata SimSurfing, TDK SEAT) to replace the band estimate and get confidence='measured'.
Input Schema
| Name | Required | Description | Default |
|---|---|---|---|
| rated_v | Yes | The part's rated DC voltage. | |
| ac_level | No | Signal magnitude class: small_signal (<50 mVrms), moderate (50-500 mVrms), or large (>500 mVrms). Small signals see less capacitance. | small_signal |
| ambient_c | No | Operating ambient temperature in °C. | |
| applied_v | Yes | DC bias actually across the part in this circuit, in volts. | |
| case_size | No | EIA case code: 0402, 0603, 0805, 1206 or 1210. Larger cases retain more capacitance under bias. | 0805 |
| dielectric | No | EIA Class II dielectric: X5R, X7R, X8R, Y5V, Z5U, or Class I C0G/NP0. | X5R |
| tolerance_pct | No | The part's capacitance tolerance in percent (e.g. 10 for ±10%). Applied at the pessimistic end. | |
| hours_in_service | No | Expected service life in hours, used for the log-time ageing term. | |
| marked_capacitance_uf | Yes | The capacitance printed on the reel, in µF. | |
| measured_retention_at_bias | No | Retention fraction (0-1] read from the real datasheet DC-bias curve at applied_v. Replaces the band estimate. |
Output Schema
| Name | Required | Description | Default |
|---|---|---|---|
| notes | Yes | Human-readable findings: which term dominates, what to change, and any caveat. | |
| source | Yes | The measurements and standards the model is calibrated against. | |
| rated_v | Yes | The part's rated DC voltage. | |
| loss_pct | Yes | Percentage of the marked value that is lost. | |
| ambient_c | Yes | Operating ambient used. | |
| applied_v | Yes | DC bias across the part that was analysed. | |
| case_size | Yes | EIA case code analysed. | |
| confidence | Yes | How trustworthy the number is: 'measured' from a datasheet curve, 'band' from a published retention range, 'physical' for Class I parts where the loss is zero by physics. | |
| dielectric | Yes | EIA dielectric class analysed. | |
| ageing_factor | Yes | Retention after the service life, log-time law. | |
| dc_bias_factor | Yes | Retention from DC bias alone — usually the dominant term. | |
| ac_level_factor | Yes | Retention from AC signal magnitude (ferroelectric hysteresis). | |
| hours_in_service | Yes | Service life used for the ageing term. | |
| tolerance_factor | Yes | Retention at the pessimistic end of the part tolerance. | |
| retention_fraction | Yes | effective / marked, after every loss mechanism. | |
| temperature_factor | Yes | Retention at the operating temperature, worst-case end of the TCC band. | |
| marked_capacitance_uf | Yes | The value printed on the reel. | |
| effective_capacitance_uf | Yes | The capacitance the circuit actually gets. |