PDK Support Matrix

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CircuitOpt uses per-device model bindings. A circuit may bind different devices to different registered model types, although most practical circuits use one process consistently.

Capability Matrix

Process	Model keys	Device backend	DC / AC / Noise	Transient	PSS / PAC / PNoise	External prerequisites
AT4000TG	at4000tg.pmos	Built-in calibrated PMOS model	Yes	Native	Yes	None
SKY130	sky130.nmos, sky130.pmos	Bundled resolved cards + native Berkeley BSIM4.5	Yes	Compiled Rust core + native C BSIM4 BE/Gear2	Native terminal backend; validate each periodic topology	None for a released wheel; external tools only for new-card extraction
FreePDK45	freepdk45.nmos, freepdk45.pmos	Flat-card loader + native Berkeley BSIM4.5	Yes	Compiled Rust core + native C BSIM4 BE/Gear2	Native terminal backend; validate each periodic topology	FreePDK45 cards; none else for a released wheel
FreePDK45 oracle	freepdk45_ngspice.nmos, freepdk45_ngspice.pmos	Cached ngspice-C grid / complete-deck oracle	Oracle only	Oracle only	Not the default periodic backend	FreePDK45 cards and ngspice
TSMC28HPC+ core	tsmc28hpcp.nmos, tsmc28hpcp.pmos	Internal HSPICE frontend + native Berkeley BSIM4.5	Yes	Compiled Rust core + native C BSIM4 BE/Gear2	Yes	Licensed supported model file; none else for a released wheel
TSMC28HPC+ oracle	tsmc28hpcp_ngspice.nmos, tsmc28hpcp_ngspice.pmos	Explicit ngspice comparison path	Oracle only	Oracle only	Not the default periodic backend	Licensed model file and ngspice

Building circuitopt_core from a source checkout (instead of installing a released wheel) additionally needs a Rust toolchain (rustup) and a C compiler for the vendored BSIM4.5 sources (maturin develop --release -m rust/crates/co-py/Cargo.toml); see Getting Started.

Prebuilt circuitopt_core wheels are published on the GitHub Release for Linux, macOS, and — starting with this release, CI-built as the first Windows build — Windows (win_amd64, abi3-py310); installing one needs neither a Rust toolchain nor a C compiler.

“Supported” means the backend is connected to the analysis path. It does not mean foundry sign-off equivalence. Each topology still needs regression against an appropriate reference.

Process Details

AT4000TG

• Default process when a transistor is not listed in the JSON models block.
• PMOS-only.
• Calibrated against archived Cadence Spectre references for the included AFE and chopper cases.
• Corners: typical, slow, fast.
• The generic mc command currently targets this continuous mismatch model.

SKY130

• Loads bundled, geometry-resolved BSIM4.5 cards and evaluates them directly with the same in-process native C backend used by FreePDK45 and TSMC28HPC+.
• Normal DC, AC, noise, transient, PSS, PAC, and PNoise runs do not launch an external simulator.
• This is a useful local optimization model, not a bit-exact replacement for the official SKY130 simulator model.
• Corners accepted by the circuit flow: tt, ss, ff, sf, fs.
• The repository includes the resolved cards used by its examples. For a new geometry/corner that has no card, explicitly run circuitopt.sky130_model.extract_sky130_card() with a local SKY130/ngspice installation and point SKY130_CARD_DIR at the generated card directory.

FreePDK45

• Parses the flat level-54 VTG cards directly and evaluates them with the in-process Berkeley BSIM4.5 kernel.
• The cards declare BSIM4 version=4.0. In the bundled Berkeley source the version field is metadata rather than an equation switch; single-device Id/gm/gds, noise, and 5T OTA AC are regression-checked against ngspice.
• The native backend exposes full four-terminal current, conductance, charge, capacitance, and correlated noise for DC, AC, noise, transient, and periodic analyses.
• The fixed-grid transient hot path runs Newton iteration and matrix stamping inside the compiled Rust core (co-core calling co-bsim4 in-process); the Python-facing compact_models/bsim4/native.py module binds the same compiled ABI through ctypes (a void * function-pointer interface) for single-device op-point/AC/noise calls outside the transient loop. As of v2.0.0 rust is the sole engine; there is no runtime compiler step and no Python numeric fallback.
• freepdk45_ngspice.* and the full-circuit ngspice helpers remain available as independent regression oracles. Import circuitopt.freepdk45_model to register the oracle-only model keys. They are optional for normal simulation.
• Corners: nom, tt, ss, ff, sf, fs.
• tt aliases nom; sf selects NMOS slow plus PMOS fast, and fs the reverse.
• Generic silicon mismatch semantics are not yet implemented through circuit-opt mc.

TSMC28HPC+

• Supports the 0.9 V nch_mac and pch_mac core wrappers from the documented 1d8 HSPICE model file.
• The internal parser resolves .lib sections, parameters, subcircuits, macros, and geometry bins in memory.
• The native backend exposes four-terminal current, conductance, charge, capacitance, and correlated noise.
• Transient uses the same compiled Rust-to-C BSIM4 bridge as FreePDK45.
• Corners: tt, ss, ff, sf, fs; nom aliases tt.
• Temperature is passed in kelvin at the device binding API.
• The current adapter does not claim support for IO devices, RF devices, SRAM, eFuse, reliability models, statistical sections, layout extraction, or sign-off checks from the full iPDK.
• Import circuitopt.tsmc28_model only when the tsmc28hpcp_ngspice.* oracle model keys are required.
• See the TSMC28HPC+ Native Adapter.

JSON Binding

{
  "devices": [
    {
      "name": "MN",
      "drain": "OUT",
      "gate": "IN",
      "source": "GND",
      "W": 1.0,
      "L": 0.03
    },
    {
      "name": "MP",
      "drain": "OUT",
      "gate": "IN",
      "source": "VDD",
      "W": 2.0,
      "L": 0.03
    }
  ],
  "models": {
    "MN": {"pdk": "tsmc28hpcp", "model": "nmos",
           "section": "inherit", "bin": "auto"},
    "MP": {"pdk": "tsmc28hpcp", "model": "pmos",
           "section": "inherit", "bin": "auto", "vb": 0.9}
  }
}

Geometry is expressed in micrometres. Model-specific constructor options are documented under models in the Circuit JSON Format.

Path Resolution

Input	Resolution
General PDK root	PDK_ROOT, then active/project virtual-environment pdk/
Additional SKY130 resolved cards	SKY130_CARD_DIR, then bundled package cards
TSMC model directory	TSMC28_MODEL_DIR, TSMC28_PDK_ROOT, project-local ignored entry, then PDK_ROOT/tsmc28hpcp
ngspice	NGSPICE_BIN, virtual-environment locations, then PATH

What CircuitOpt Does Not Replace

CircuitOpt is a local simulation and optimization framework. It does not replace official PDK installation, schematic/layout libraries, DRC, LVS, parasitic extraction, EM/IR, aging, reliability, statistical sign-off, or foundry-approved tapeout flows.