Understanding MOSFET Calculations

A MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) is a voltage-controlled current device.

Drain Current Formulas:

1. Triode Region (for low V_DS):

I_D = k[2(V_GS - V_T)V_DS - V_DS²]

2. Saturation Region (for high V_DS):

I_D = k(V_GS - V_T)² / 2

Example Calculations:

Example 1 (Triode Region):

Assume V_T = 1 V, k = 0.1 A/V², V_GS = 5 V, V_DS = 3 V.

Using the formula:

I_D = 0.1 * [2(5 - 1)(3) - 3²] = 0.1 * [8 * 3 - 9] = 0.1 * (24 - 9) = 0.1 * 15 = 1.5 A

Example 2 (Saturation Region):

Assume V_T = 2 V, k = 0.2 A/V², V_GS = 10 V, V_DS = 15 V.

Using the formula:

I_D = 0.2 * (10 - 2)² / 2 = 0.2 * 8² / 2 = 0.2 * 64 / 2 = 6.4 A

Notes:

• If V_DS is much greater than V_T, MOSFET usually operates in the saturation region.
• If V_DS is close to or less than V_T, MOSFET operates in the triode region.