Source: https://guthlabs.ai/docs/instruments/op-amp-noise-estimator-input-referred/
instrument / verified-clean
# Op-Amp Noise Estimator (input-referred)
The current ledger marks this instrument verified clean within the source-bound verification corpus.
Status: **VERIFIED_CLEAN**Lifecycle: **verified-clean**
## Inspectable records
[01**Overview**Purpose and lifecycle]()[02**Mechanism**Method and assumptions]()[03**Implementation**Binding and validation]()[04**Qualification**Evidence and errata]()
## Ledger state
The current ledger marks this instrument verified clean within the source-bound verification corpus.
**Area**: Electrical & Electronics Engineering — Circuits, Power Systems, Electronics Lab
**Tranche**: tranche-5
**Evidence ID**: t5-203
**Ledger rows**: 1
No ledger note is attached.
## Review findings
The core white-noise formula is correct under the stated unit and spectral assumptions. Verdict is NEEDS_REVIEW because the specification advertises optional current-noise/source-resistance and 1/f-corner functionality without defining their formulas, required parameters, or integration model.
### Formula and scope findings
- Vn_rms = en × √BW is correct only for constant white voltage-noise density and a bandwidth expressed in Hz; it does not calculate total noise when 1/f noise is significant.
- The optional current-noise and source-resistance inputs have no stated formula. Their contribution would require at least (in)^2 × R_source^2 added to the mean-square voltage noise, with resistance in ohms and current-noise density in A/√Hz.
- The optional 1/f corner correction is unspecified: no 1/f noise model, integration limits, or formula are provided, so that feature cannot be verified.
- The specification says total input-referred noise while labeling the calculation a simplified white-noise-band estimate; this scope limitation must be explicit in the user-facing result.
### Unit assumptions
- en is a one-sided white voltage-noise density in V/√Hz, commonly entered in nV/√Hz and converted using 1 nV = 1e-9 V.
- BW is the integrated noise bandwidth in Hz, not merely a nominal -3 dB bandwidth unless those are explicitly treated as equivalent.
- The output Vn_rms is in volts RMS; outputs may also be displayed in µV RMS or nV RMS after conversion.
- BW must be finite and nonnegative; en must be finite and nonnegative.
- If current-noise and source-resistance contributions are later supported, current noise must be in A/√Hz, source resistance in Ω, and temperature-dependent resistor thermal noise requires an explicitly specified temperature in kelvin.
## Boundary hardening
**BREAK_CLAIMED** · SELF_FLAGGED
A negative bandwidth produces an undefined real-valued square root and must be rejected. The signed-density probe also exposes a convention hazard: literal signed arithmetic can produce a negative RMS result unless the instrument enforces or applies a nonnegative-magnitude convention.
## Errata and corrections
No applied erratum is attached to this unique-name record.
## Inspectable example
4 review vectors are recorded. One source-bound sample is shown below.
````
{
"inputs": {
"voltage_noise_density": 8,
"voltage_noise_density_unit": "nV/√Hz",
"bandwidth": 20000,
"bandwidth_unit": "Hz"
},
"expected_outputs": {
"total_rms_noise_voltage": 0.00000113137085,
"total_rms_noise_voltage_unit": "V RMS",
"display_value": 1.13137085,
"display_unit": "µV RMS"
},
"working": "Convert en: 8 nV/√Hz = 8 × 10^-9 V/√Hz. √BW = √20000 = 141.4213562 √Hz. Vn_rms = (8 × 10^-9) × 141.4213562 = 1.13137085 × 10^-6 V RMS = 1.13137085 µV RMS."
}
````
## Related workflows
No source-defined multi-instrument workflow membership is recorded.
## Sources and evidence
These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.
- `VERIFIED_LEDGER.json · VERIFIED_CLEAN`
- `evidence-tranche5/tranche5-results.json`
- `BOUNDARY_HAZARD_CATALOG.json`