Electronics Basics #28 | Gate-Source Short: Depletion MOSFET DC Analysis

Instructor: Dr. Süleyman Burak ÇELİK

Why does a depletion MOSFET conduct when its gate is shorted to its source? Read the original circuit, establish VGS=0 from the wire connection, calculate the candidate current and resistor drop, then check the saturation condition. Original lesson43: 20V supply, RD1.5kΩ, IDSS10mA, VP−4V; no gate or source resistor. Ideal checked result: ID10mA and VDS5V. The saturation boundary is4V, so the candidate is consistent. A load-line plot shows the circuit relation meeting the valid zero-bias saturation-current model. Gate current is not drain current; a gate-source short is not a drain-source short. Ideal saturation model with negligible gate leakage and suitable real-device ratings assumed. The shaded graph region is not modeled as constant saturation current. Chapters: 0:00 The goal: distinguish a gate short from a channel short 1:04 The wire fixes the control voltage, not the drain current 1:41 At zero bias, a depletion channel is already present 2:52 Find the resistor drop, then the transistor voltage 4:07 Check the saturation assumption explicitly 5:27 A simple answer still needs a physical check