Source: https://guthlabs.ai/docs/instruments/op-amp-bandwidth-gain-bandwidth-product-checker/mechanism/

instrument mechanism / verified-clean

# Op-Amp Bandwidth / Gain-Bandwidth Product Checker mechanism

The inspectable method record for Op-Amp Bandwidth / Gain-Bandwidth Product Checker, kept separate from implementation and qualification.

Status: **VERIFIED_CLEAN**Lifecycle: **verified-clean**

## Model scope

The arithmetic formula is acceptable as a first-order estimate only after the gain definition, units, and op-amp model are made explicit. The empty honest_label is a concern: the interface should state that this is an approximate GBW-based estimate, not a guaranteed usable bandwidth.

- BW=GBW/Av is a standard first-order approximation for a voltage-feedback op-amp with a single dominant pole, where Av is the positive closed-loop noise gain magnitude, not necessarily the signal gain magnitude.

- For an inverting amplifier, the relevant gain for bandwidth is the noise gain 1+Rf/Rin, not the magnitude of the signal gain Rf/Rin.

- The label 'maximum usable closed-loop bandwidth' is too strong: actual bandwidth also depends on compensation, additional poles, feedback network loading, capacitive loading, stability margin, slew rate, output amplitude, and the required accuracy.

- The requested 'feasibility warning' has no defined input target bandwidth or warning threshold, so the instrument cannot determine feasibility from the supplied inputs alone.

- The specification does not define valid gain constraints; zero gain causes division by zero, and negative or nonnumeric gain values are ambiguous.

## Units and conventions

- GBW and the resulting bandwidth must use the same frequency unit; the test outputs below normalize bandwidth to Hz.

- Av must be a dimensionless voltage gain magnitude expressed as V/V, not dB.

- The formula assumes a voltage-feedback op-amp with approximately constant gain-bandwidth product and a dominant-pole response.

- For an inverting configuration, Av must be interpreted as noise gain rather than signal gain.

- The formula estimates the approximate closed-loop -3 dB bandwidth, not a guaranteed usable bandwidth under all load, amplitude, accuracy, or stability conditions.

## Inspectable vector

One of 4 source-bound review vectors:

````
{
  "inputs": {
    "gbw": 1,
    "gbw_unit": "MHz",
    "desired_gain": 10
  },
  "expected_outputs": {
    "achievable_bandwidth": 100000,
    "bandwidth_unit": "Hz",
    "feasibility_warning": "Cannot be determined: no target bandwidth or feasibility criteria were supplied."
  },
  "working": "1 MHz = 1,000,000 Hz. BW = GBW / Av = 1,000,000 Hz / 10 = 100,000 Hz."
}
````

## Failure boundary

**BREAK_CLAIMED** · SELF_FLAGGED

The formula is undefined when desired gain is zero, so the instrument must reject Av = 0 or explicitly report an undefined result. The specification also does not define a formula branch, a feasibility-warning threshold, or whether gain should be signed or treated by magnitude.

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/op-amp-bandwidth-gain-bandwidth-product-checker/>)[03**Implementation**](<https://guthlabs.ai/docs/instruments/op-amp-bandwidth-gain-bandwidth-product-checker/implementation/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/op-amp-bandwidth-gain-bandwidth-product-checker/qualification/>)

## Sources and evidence

These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.

- `VERIFIED_LEDGER.json`

- `evidence-tranche4/tranche4-results.json`

- `BOUNDARY_HAZARD_CATALOG.json`