GUI-based OTA sizing tool. Automates transistor-level design of CMOS Operational Transconductance Amplifiers using the gm/ID methodology. Delivers a ready-to-simulate design in minutes.
14 industry-standard OTA topologies — from Differential Amplifier to Class AB Folded Cascode. Both NMOS and PMOS input stage configurations supported across all topologies.
Uses MOS characteristic data files extracted from foundry SPICE models to estimate transistor sizes and DC current — no hand calculations, no guesswork.
Auto-generates ready-to-simulate SPICE subcircuit netlists with transistor instances, biasing, and PDK compatibility notes included.
Auto Mode autonomously explores the complete transistor sizing space and simultaneously returns three optimised solutions — Low Power, Balanced, and High Slew Rate.
Manual Mode lets you set channel length and overdrive voltage directly for targeted fine-tuning of transistor sizes, DC current, and performance specifications.
Every Auto Mode run returns three SPICE netlists simultaneously — Low Power, Balanced, and High Slew Rate — each meeting your specified targets.
Complete OTA design ready in minutes — not hours or days. Eliminates the iterative hand-calculation loop entirely.
Comprehensive design summary in CSV format — transistor sizes, performance metrics, noise summary, and voltage ranges, all in one output directory.
Intuitive graphical interface — no scripting or command-line required. All fields are self-explanatory, with real-time console output during the design run.
| Parameter | Value |
|---|---|
| Version | 2026.0 |
| Platform | Ubuntu 20.04 LTS or later (Linux only) |
| Distribution | ZIP archive — self-contained executable |
| Memory | 4 GB minimum; 8 GB recommended |
| Disk space | ~200 MB for AmpForge + .mdat files |
| External dependency | NGSPICE (for MOS Characterizer only) |
| Internet | One-time only (Machine ID + licence file) |
| Licence type | Node-locked (.lic file, machine-specific) |
All 14 topologies support both NMOS and PMOS input stage configurations.
| No. | Topology | No. | Topology |
|---|---|---|---|
| 1 | Differential Amplifier OTA | 8 | Two Stage Miller RHP Cancel OTA |
| 2 | Symmetrical OTA | 9 | Two Stage Cascode I/P Miller OTA |
| 3 | Symmetrical with Cascode Output OTA | 10 | Two Stage Cascode I/P Miller Null Resistor OTA |
| 4 | Folded Cascode OTA | 11 | Two Stage Cascode I/P Miller RHP Cancel OTA |
| 5 | Recycling Folded Cascode OTA | 12 | Two Stage Folded Cascode I/P Miller OTA |
| 6 | Two Stage Miller OTA | 13 | Class AB Two Stage Miller OTA |
| 7 | Two Stage Miller Null Resistor OTA | 14 | Class AB Folded Cascode Two Stage Miller OTA |
The trial licence provides access to 7 topologies: Differential Amplifier, Symmetrical, Folded Cascode, Two Stage Miller, Two Stage Miller Null Resistor, Two Stage Miller RHP Cancel, and Class AB Two Stage Miller. The remaining 7 — Symmetrical with Cascode Output, Recycling Folded Cascode, Two Stage Cascode I/P Miller variants, Two Stage Folded Cascode I/P Miller, and Class AB Folded Cascode Two Stage Miller — require the full licence.
In Auto Mode, the Design Synthesizer simultaneously returns three SPICE netlists — each meets your specifications, optimised for a different operating point.
| Specification | Low Power | Balanced | High Slew Rate |
|---|---|---|---|
| Overdrive Voltage (VOV) | Least | Moderate | Highest |
| Transition Frequency (fT) | Least | Moderate | Highest |
| Power consumption | Least | Moderate | Highest |
| I/O Common Mode Voltage | Highest | Moderate | Least |
| Open Loop DC Gain potential | Highest | Moderate | Least |
| W/L Ratios | Highest | Moderate | Least |
| Slew Rate | Least | Moderate | Highest |
Pre-built .mdat files are included for three process nodes. For any other PDK, run the MOS Characterizer once to generate the database.
n18, p18, nhv, phv, n5v, p5v models.
sg13_lv_nmos, sg13_lv_pmos, HV variants. Open PDK.
nmos_3p3, pmos_3p3, 6V variants. Open PDK.
The following results are from worked Example 1 in the AmpForge User Guide — Two Stage Miller RHP Cancel OTA, SCL 180nm, Auto Mode, High Slew Rate solution.
| Parameter | Target | AmpForge Achieved | SPICE Simulation |
|---|---|---|---|
| Open Loop Gain (dB) | 55 | 55.25 | 55.38 |
| Unity Gain Bandwidth (MHz) | 1000 | 1000 | 904 |
| Phase Margin (deg) | 60 | 55.31 | 56.57 |
| Slew Rate (V/µs) | 350 | 352 | 357 |
| Input Ref. Thermal Noise PSD (nV/√Hz) | 6 | 5.29 | 5.72 |
| Input-referred Flicker Noise PSD @ 1Hz (µV/√Hz) | — | 17.5 | 17.81 |
| Total OTA plus Biasing Ckt. Current (mA) | — | 1.74 | 1.7 |
Technology: SCL 180nm CMOS · PMOS input stage · CL = 2pF
Trial and full licences available. 48-hour turnaround on the .lic file.
Request Licence