MOSFET Drain Current Visualizer

Control Panel

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Device Type

Operating Mode

Terminal Voltages

V_G Gate Voltage (V_G)
The voltage applied to the gate terminal of the MOSFET, measured relative to ground.

Controls the channel conductivity and thus the drain current.

V_D Drain Voltage (V_D)
The voltage applied to the drain terminal, measured relative to ground.

Current flows from drain to source in NMOS (when ON).

V_S Source Voltage (V_S)
The voltage at the source terminal, measured relative to ground.

Often connected to ground (0V) for NMOS, or to V_DD for PMOS.

Device Parameters

V_th Threshold Voltage (V_th)
The minimum V_GS required to create a conducting channel.

NMOS Enhancement: V_th > 0
NMOS Depletion: V_th < 0
PMOS Enhancement: V_th < 0
PMOS Depletion: V_th > 0

k Transconductance Parameter (k)

k = μ_n · C_ox · (W/L)

Where:
• μ_n = electron mobility (cm²/V·s)
• C_ox = oxide capacitance per unit area (F/cm²)
• W = channel width
• L = channel length

Determines the current-carrying capability of the MOSFET. Higher k means more current for the same voltages.

mA/V²

MOSFET Model

NMOS: ON when V_GS > V_th

Enhancement: V_th > 0
Depletion: V_th < 0

PMOS: ON when V_GS < V_th

Enhancement: V_th < 0
Depletion: V_th > 0

I-V Characteristics (Drag Graph to Adjust)

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↔ Horizontal: Vds | ↕ Vertical: Vgs

Computed Values

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V_GS Gate-Source Voltage
V_GS = V_G − V_S

The voltage difference between gate and source. This is what controls whether the MOSFET is ON or OFF. 3.00 V

V_DS Drain-Source Voltage
V_DS = V_D − V_S

The voltage across the channel. Determines the operating region (triode vs saturation). 2.50 V

I_D Drain Current

Cutoff: I_D = 0

Triode:
I_D = k[(V_GS−V_th)V_DS − ½V_DS²]

Saturation:
I_D = ½k(V_GS−V_th)² 0.000 mA

Region Operating Region

Cutoff: V_GS ≤ V_th
Triode: V_DS < V_OV
Saturation: V_DS ≥ V_OV —

V_OV Overdrive Voltage
V_OV = V_GS − V_th

The "excess" voltage above threshold. Determines the boundary between triode and saturation regions. 2.00 V

Cutoff

Triode

Saturation