Electronics Basics #13 | Zener Regulator: The Safe Window (R_L & V_in Ranges)

Instructor: Dr. Süleyman Burak ÇELİK

A Zener only regulates inside a window — and that window is set by the same two limits every time. Find both edges and you've defined the regulator. The two edges: - Lower edge — the Zener is just barely on (its current near zero). Beyond it (load too heavy or input too low) the node drops under V_Z and the Zener shuts off. - Upper edge — the Zener is at its maximum current I_Z(max), its power limit. Beyond it (load too light or input too high) the Zener overheats. Between the edges, the output is a flat plateau at V_Z. Worked twice, every step shown: - Case A — fixed input, variable load (V_i = 50 V, R = 1 kΩ, V_Z = 10 V, I_Z(max) = 32 mA). I_R is fixed at 40 mA. Result: R_L from 250 Ω to 1250 Ω. - Case B — fixed load, variable input (R = 220 Ω, V_Z = 20 V, I_Z(max) = 60 mA, R_L = 1.2 kΩ). I_L is fixed at 16.67 mA. Result: V_in from 23.67 V to 36.87 V. The takeaway: find the two edges — Zener just on, and Zener at I_Z(max). Reference: Boylestad, Electronic Devices and Circuit Theory