Vol. IV — Electronics · Tool
A series resistor feeds an unregulated Vin into a reverse-biased zener that clamps the rail near Vz. Add a load and the diode takes whatever current is left. Change Vin, Vz, Rs, and Rload — Vout, Iz, and power update as you type.
Ideal shunt model: when Vin is high enough, Vout sits at Vz. Current through Rs is Irs = (Vin − Vz) / Rs. The load takes Iload = Vz / Rload; the zener takes Iz = Irs − Iload. If Iz would go negative, the load is too heavy — Vout falls below Vz (dropout / overload in this simple model).
No-load mode sets Rload to infinity so Iz = Irs — useful for picking Rs from a power budget. Watch Pz = Vz · Iz and Prs = Irs² · Rs against the parts you actually have. Pair with the rectifier, voltage divider, and circuit explorer Diode lesson.