Drain Current Of FET Calculator

FET Drain Current Formula:

\[ I_D = I_{DSS} \times \left(1 - \frac{V_{DS}}{V_{cut-off}}\right)^2 \]

Drain Current (I_D):

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1. What is the FET Drain Current Equation?

The FET Drain Current equation calculates the drain current in a field-effect transistor based on zero bias drain current, drain-source voltage, and cut-off voltage. This formula is essential for analyzing FET operation in various circuit configurations.

2. How Does the Calculator Work?

The calculator uses the FET Drain Current equation:

\[ I_D = I_{DSS} \times \left(1 - \frac{V_{DS}}{V_{cut-off}}\right)^2 \]

Where:

\( I_D \) — Drain Current (A)
\( I_{DSS} \) — Zero Bias Drain Current (A)
\( V_{DS} \) — Drain-Source Voltage (V)
\( V_{cut-off} \) — Cut-off Voltage (V)

Explanation: The equation describes the relationship between drain current and drain-source voltage in the saturation region of FET operation, showing how current decreases as drain-source voltage approaches the cut-off voltage.

3. Importance of Drain Current Calculation

Details: Accurate drain current calculation is crucial for designing and analyzing FET-based circuits, determining operating points, and ensuring proper transistor biasing in amplifier and switching applications.

4. Using the Calculator

Tips: Enter zero bias drain current in amperes, drain-source voltage in volts, and cut-off voltage in volts. All values must be positive and non-zero for accurate calculation.

5. Frequently Asked Questions (FAQ)

Q1: What is zero bias drain current (I_DSS)?
A: I_DSS is the maximum drain current that flows when the gate-source voltage is zero and the drain-source voltage is sufficiently high to keep the FET in saturation.

Q2: What is cut-off voltage in FET?
A: Cut-off voltage (also called pinch-off voltage) is the gate-source voltage at which the drain current becomes approximately zero, effectively turning off the FET.

Q3: When is this equation applicable?
A: This equation is valid when the FET is operating in the saturation region, where V_DS > V_GS - V_cut-off.

Q4: Are there limitations to this equation?
A: This simplified model doesn't account for channel length modulation, temperature effects, or other second-order effects that may be significant in precise calculations.

Q5: Can this calculator be used for both JFET and MOSFET?
A: This equation is primarily used for JFETs. While similar principles apply to MOSFETs, the exact equations may differ based on the specific MOSFET type and operating region.