Schmitt Trigger Threshold Calculator

Inspectable records

Ledger state

The current ledger marks this instrument verified with errata that must be applied at binding time.

Area

Electrical & Electronics Engineering — Circuits, Power Systems, Electronics Lab

Tranche

tranche-5

Evidence ID

t5-189

Ledger rows

1

No ledger note is attached.

Review findings

The instrument cannot honestly claim to compute general op-amp Schmitt-trigger upper and lower trip points until the topology, resistor placement, reference voltage, and positive/negative saturation definitions are specified. The provided vectors use the additional symmetric zero-reference assumption. The original second-vector value was corrected in the working and expected outputs to maintain arithmetic accuracy.

Formula and scope findings

• VTH=Vsat×R1/(R1+R2) is valid only for a specific zero-reference Schmitt-trigger topology and resistor placement; it is not a universal op-amp Schmitt-trigger threshold formula.
• The specification does not define the reference configuration, so VTH+ and VTH− cannot be uniquely determined. A nonzero reference voltage changes both thresholds.
• Only one Vsat is provided, but real circuits may have unequal positive and negative saturation levels. The formula must specify whether Vsat is a positive magnitude, a signed rail, or separate Vsat+ and Vsat− values.
• hysteresis=VTH_high−VTH_low is standard, but VTH_high and VTH_low are not independently defined by the supplied formula. For a symmetric zero-reference circuit, the result would be 2×Vsat×R1/(R1+R2).

Unit assumptions

• Vsat is treated as a positive voltage magnitude in volts.
• R1 and R2 must use the same resistance unit; only their ratio matters.
• The test-vector calculations assume a zero-reference, symmetric Schmitt-trigger configuration in which VTH+=+Vsat×R1/(R1+R2) and VTH−=−Vsat×R1/(R1+R2).
• Positive resistance values are assumed unless explicitly testing a boundary case.

Boundary hardening

BREAK_CLAIMED · SELF_FLAGGED

The denominator can be forced to zero with R1+R2=0, producing an undefined threshold that must be rejected. In addition, the specification provides only one threshold formula and does not explicitly define how VTH_plus and VTH_minus, reference polarity, or signed hysteresis are derived.

Errata and corrections

Tranche errata

Inspectable example

4 review vectors are recorded. One source-bound sample is shown below.

{
  "inputs": {
    "Vsat": 5,
    "R1": 10000,
    "R2": 20000,
    "reference_config": "zero reference; symmetric rails; R1 and R2 in ohms"
  },
  "expected_outputs": {
    "VTH_plus": 1.6666666667,
    "VTH_minus": -1.6666666667,
    "hysteresis": 3.3333333333
  },
  "working": "R1+R2=10000+20000=30000 ohms. VTH magnitude=5×10000/30000=50000/30000=1.6666666667 V. VTH+=+1.6666666667 V. VTH−=−1.6666666667 V. Hysteresis=VTH+−VTH−=1.6666666667−(−1.6666666667)=3.3333333333 V."
}

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_WITH_ERRATA
• evidence-tranche5/tranche5-results.json
• BOUNDARY_HAZARD_CATALOG.json