Precision shunt reference
4 parts
The TL431-class circuit: a precision shunt reference clamps its cathode 2.5 V above its anode while the series 1 kΩ absorbs everything the supply throws at it. The supply swings 6–12 V at 200 Hz, yet the output moves just 5.2 mV — 0.86 mV per volt of line change — while the load draws a steady 1.16 mA. VREF is the solver's zener reverse-breakdown path with a deliberately sharp knee: a shunt reference IS a tight zener, so this is real junction physics honestly reused, not a macromodel. At milliamp bias the exponential knee sits slightly above nominal — the measured rail is 2.559–2.564 V, not 2.500.
- V1 3V·200Hz
- R1 1kΩ
- VREF1 →2.5V
- R2 2.2kΩ
