š MOSFET Calculator
Enter your MOSFET’s gate, threshold, and drain voltages along with its transconductance parameter to find the drain current and operating region.
What This Calculator Does
This calculator estimates an enhancement-mode MOSFET’s drain current and tells you which region it’s operating in — cutoff, triode (linear), or saturation — using the standard square-law transistor model taught in electronics courses.
The Formula
The overdrive voltage is Vov = Vgs − Vth. If Vov ≤ 0, the device is off (cutoff). Otherwise, if Vds is less than Vov, the MOSFET is in the triode region and Id = k × (Vov × Vds − Vds²/2). If Vds is greater than or equal to Vov, it’s in saturation and Id = 0.5 × k × Vov², where k is the device’s transconductance parameter (k = μCoxW/L for a given process and geometry).
- Cutoff: no channel forms, essentially zero current flows.
- Triode: the MOSFET behaves like a voltage-controlled resistor.
- Saturation: current depends mainly on Vgs, used for amplification and switching.
This simplified square-law model ignores second-order effects like channel-length modulation; it’s intended for general electronics education and initial design estimates, not precise datasheet-level simulation.