Op-Amp Bandwidth / Gain-Bandwidth Product Checker mechanism

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

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