Source: https://guthlabs.ai/docs/instruments/class-a-b-ab-amplifier-efficiency-dissipation-estimator/mechanism/

instrument mechanism / verified-clean

# Class A/B/AB Amplifier Efficiency & Dissipation Estimator mechanism

The inspectable method record for Class A/B/AB Amplifier Efficiency & Dissipation Estimator, kept separate from implementation and qualification.

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

## Model scope

The honest-label text is directionally correct but should explicitly state the assumptions behind 25%, 50%, and 78.54%, distinguish theoretical maximum efficiency from actual operating efficiency, and identify the selected Class A topology. The exact ambiguity requiring resolution is: whether Class A means transformerless 25% or transformer-coupled 50%, and what ideal conduction-angle model defines Class AB.

- Class A efficiency is topology-dependent: approximately 25% applies to a transformerless resistive-load stage, while approximately 50% applies to an ideal transformer-coupled stage; the specification does not identify which one is used.

- Class AB has no separate stated formula. Its ideal maximum is commonly treated as approaching the Class B limit of pi/4 (78.54%), but the result depends on the assumed conduction angle and bias.

- Pdiss = Psupply - Pout is a correct power-balance formula only when Psupply means total DC input power. Supply voltage alone or per-rail voltage is insufficient.

- The claimed theoretical efficiency is not necessarily the actual efficiency at a specified operating point. Actual efficiency requires eta_actual = Pout/Psupply.

## Units and conventions

- Supply voltage is total DC voltage across the amplifier supply, not one rail of a split supply; if using split rails, Psupply must be computed from the sum of each rail's V times its corresponding current.

- Supply current is total DC input current in amperes, so Psupply = Vsupply x Isupply in watts.

- Pout is real load power in watts, normally RMS sinusoidal power for the ideal Class B limit.

- Load is in ohms and is relevant to output-voltage/current feasibility; it does not by itself determine efficiency.

- Class B and ideal Class AB use eta_max = pi/4 = 0.785398, or 78.54%, under ideal push-pull, resistive-load, sinusoidal, maximum-undistorted-swing assumptions.

- Class A test cases explicitly distinguish transformerless 25% operation from transformer-coupled 50% operation.

## Inspectable vector

One of 4 source-bound review vectors:

````
{
  "inputs": {
    "class": "B",
    "supply_voltage_V": 24,
    "supply_current_A": 1,
    "output_power_W": 12,
    "load_ohm": 8
  },
  "expected_outputs": {
    "theoretical_max_efficiency_percent": 78.54,
    "actual_efficiency_percent": 50,
    "supply_power_W": 24,
    "dissipation_W": 12
  },
  "working": "Theoretical efficiency = (pi/4) x 100 = 0.785398 x 100 = 78.54%. Supply power = 24 V x 1 A = 24 W. Actual efficiency = 12 W / 24 W x 100 = 50%. Dissipation = 24 W - 12 W = 12 W."
}
````

## Failure boundary

**BREAK_CLAIMED** · SELF_FLAGGED

A zero-load input produces an undefined output-power calculation and must be rejected. The Class A efficiency branch is also underspecified because the specification permits both 25% and 50% maxima, while signed versus magnitude output-power conventions produce materially different results.

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/class-a-b-ab-amplifier-efficiency-dissipation-estimator/>)[03**Implementation**](<https://guthlabs.ai/docs/instruments/class-a-b-ab-amplifier-efficiency-dissipation-estimator/implementation/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/class-a-b-ab-amplifier-efficiency-dissipation-estimator/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-tranche5/tranche5-results.json`

- `BOUNDARY_HAZARD_CATALOG.json`