Verified calculation capability

MOSFET junction temperature Calculation Capability

Steady-state Tj = Ta + P·Rth. Effective RθJA, or case/heatsink-dominant RθJC+RθCA (not equivalent models). Mixing both paths is CONFLICTING_INPUTS. · Electrical · Mosfet

Capability ID electrical.mosfet.tj · version 1.1.2

Open calculator REST API MCP Evidence Evidence JSON CVP Manifest Review policy

Model

Junction

Junction: Tj = Ta + P · Rθ
Temperature rise: ΔT = P · Rθ
Thermal margin: Margin = Tj,max − Tj

Inputs / Outputs

Canonical symbols for this capability. Agent schemas remain the contract.

Symbol	Quantity	Unit	Role
`Ta`	—	°C	input / output
`P`	—	W	input / output
`Rth_JA`	Effective / application junction-to-ambient thermal resistance (°C/W). Datasheet JEDEC RθJA is primarily a comparison metric.	—	input / output
`Rth_JC`	Junction-to-case thermal resistance (°C/W) for a case/heatsink-dominant path.	—	input / output
`Rth_CA`	Lumped case-to-ambient (°C/W): interface + heatsink-to-ambient. Parallel PCB/package paths ignored.	—	input / output
`Tj_max`	—	°C	input / output
`Rth_C_per`	—	W	output
`path`	JA = effective junction-to-ambient; JC+CA = case/heatsink-dominant lumped single path. Not interchangeable models.	—	output
`dT`	—	°C	output
`Tj`	—	°C	output
`margin`	—	°C	output

Assumptions / Validity

Declared scope for this capability. Do not use it outside this domain.

Assumptions

Steady-state lumped thermal resistance
Rθ constant (not Zth(t))
RθJA is an effective / application value for the user's thermal environment, not a JEDEC-board package constant
JC+CA is a case/heatsink-dominant lumped single-path approximation; it does not model parallel heat-flow through PCB, leads, or package surfaces

Example

One numerical check. The calculator page holds worked steps and FAQ.

Ta=25, P=2, RthJA=40 → Tj=105, ΔT=80, margin=45 if max=150

Open this example in the calculator

Trust

CVP VERIFIED · CVP protocol 1.0.0-proposed · Engineering assurance. Computational verification is defined by CVP. Supplemental domain review (internal) and named expert review are defined by the Review policy and do not by themselves determine CVP conformance.

CVP: CVP VERIFIED · CVP protocol 1.0.0-proposed · Engineering assurance· View Manifest · CVP overview · Specification
Assurance: Engineering
Declared partition coverage: PASS · 3/3 declared partitions (ja, jc-ca, invalid-domain)
Calculation version: 1.1.2
Verification: 18/18 calculation tests · 3/3 legacy golden · 8/8 legacy boundary · 5/5 legacy property
Production surface contract: 14/14
Versions: Calculation 1.1.2 · CVP protocol 1.0.0-proposed
CVP identity: 5/5 property · digest 950f87c6bdab
Reference: O1 model · O2 expected_values · O2 numerical_behavior
Interfaces: PASS · UI (SSR) / REST / MCP
ui-ssr is query-result HTML, not a live browser session.
CVP suite: 3/3 golden · 8/8 CVP boundary · 6/6 invalid · 5/5 property · 1/1 cross-interface · 14/14 CVP contract
Supplemental domain review: Internal · Pass · electrical-engineer · CalculatorX electrical review (EE-001) · 2026-08-16
Named expert review: Not performed
Version lock: Supported (409 VERSION_MISMATCH)
Artifact consistency: Build verified · 1.1.2 (workspace artifacts agree)
Review-policy tier: Internally reviewed — catalog token internally_reviewed; supplemental; not CVP status

This calculator CURRENT · Public schema 1.1.2 matches · Semantic contract ✓ · Production attested · Public/cache ✓ · Origin ✓

Call this capability

Human page, REST, and MCP share the same engine and calculation_version. Build verified hashes workspace artifacts only. After deploy, attest:production GETs canonical URLs twice — the public/cached view an Agent actually hits, and origin — including every /capabilities/{id} HTML page. Public Capability HTML version must match catalog before production attestation passes. Live Trust rows above fetch /.well-known/calculatorx-production-attestation.json and the output schema const. Build hashes: release integrity. That proves currently published page / engine / schema / evidence / MCP agree — not that a historical version is independently immutable. Reference Calculation Standard — Production surface contract 14/14.

Tool id: mosfet-tj
Engine: mosfet-tj
REST: POST /api/v1/calc/mosfet-tj
MCP: execute_calculation with capability_id: "electrical.mosfet.tj"
Agent input schema: Canonical (MCP / Agent)
Output schema: JSON Schema (latest)
Versioned input schema: Immutable pin (1.1.2)
Versioned output schema: Immutable pin (1.1.2)

References

Human-readable sources plus CVP reference evidence classes.

Sources

Texas Instruments SPRA953D — Semiconductor and IC Package Thermal Metrics — RθJA, RθJC, and application dependence of junction-to-ambient metrics
onsemi AND9016 — MOSFET Thermal Resistance — Junction-to-case / case-to-ambient thermal path
JEDEC JESD51 series — Integrated circuit thermal measurement — Methodology for package thermal metrics

Reference evidence classes: O1 model · O2 expected_values · O2 numerical_behavior

Try with an agent

Inspect this capability via same-origin MCP, then call execute_calculation.

curl -sS -X POST 'https://www.calculatorx.com/mcp' \
  -H 'Content-Type: application/json' \
  -H 'MCP-Protocol-Version: 2026-07-28' \
  -H 'Mcp-Method: tools/call' \
  -H 'Mcp-Name: inspect_capability' \
  -d '{"jsonrpc":"2.0","id":1,"method":"tools/call","params":{"name":"inspect_capability","arguments":{"capability_id":"electrical.mosfet.tj"}}}'

Inspect the trust tier and required assurance level before execution. Pin calculation_version (1.1.2) when reproducibility matters. Full protocol notes: MCP docs.