five-transistor-ota

name	five_transistor_ota
description	Five-transistor OTA simulation and analysis skill. Use when the user wants to simulate or size a classic 5T CMOS OTA: NMOS differential input pair, PMOS current-mirror active load, and NMOS tail current transistor. Supports ngspice DC transfer, AC gain/bandwidth/phase, output-noise analysis, and first-order design interpretation. Requires ngspice on PATH and Python 3 with numpy/matplotlib/scipy.

Five-Transistor OTA Skill

Classic single-ended 5T CMOS OTA using PTM 180nm models.

Topology

             VDD
              |
       M3 PMOS mirror output      M4 PMOS diode load
              |                         |
             OUT                       NETD
              |                         |
       M0 NMOS input +           M1 NMOS input -
              \_______________________/
                         |
                        TAIL
                         |
                M5 NMOS tail source
                         |
                        VSS

Ports: INP, INN, OUT, VDD, VSS, VBIAS.

Running

cd five_transistor_ota/scripts
python run_ota.py

This runs:

• DC transfer curve around the input common-mode point.
• AC open-loop gain from differential input to output.
• Output-referred noise density and integrated RMS noise.

Outputs go to WORK/plots, WORK/logs, and WORK/netlists.

Main Scripts

Task	Script
Full simulation	run_ota.py
DC only	run_ota_dc.py
AC only	run_ota_ac.py
Noise only	run_ota_noise.py

Design Knobs

Edit scripts/ota_common.py:

• W_IN_UM, L_IN_NM, M_IN — input pair sizing.
• W_LOAD_UM, L_LOAD_NM, M_LOAD — PMOS mirror load sizing.
• W_TAIL_UM, L_TAIL_NM, M_TAIL — tail transistor sizing.
• VBIAS — tail gate bias.
• C_LOAD and R_LOAD — output loading.