Drain Current Flowing Through MOS Transistor Calculator

Drain Current Formula:

\[ I_D = \frac{W}{L} \times \mu_n \times C_{ox} \times \int_{0}^{V_{DS}} (V_{GS} - x - V_T) \, dx \]

Channel Width (W):

Channel Length (L):

Electron Mobility (μn):

m²/V·s

Oxide Capacitance (Cox):

Gate Source Voltage (VGS):

Threshold Voltage (VT):

Drain Source Voltage (VDS):

Drain Current (ID):

Unit Converter ▲

Unit Converter ▼

From:	To:

1. What is the Drain Current Equation?

The drain current equation calculates the current flowing from drain to source in a MOSFET transistor. It's based on the device's physical parameters and operating conditions, providing insight into transistor performance and behavior.

2. How Does the Calculator Work?

The calculator uses the drain current equation:

\[ I_D = \frac{W}{L} \times \mu_n \times C_{ox} \times \int_{0}^{V_{DS}} (V_{GS} - x - V_T) \, dx \]

Where:

\( W \) — Channel Width (m)
\( L \) — Channel Length (m)
\( \mu_n \) — Electron Mobility (m²/V·s)
\( C_{ox} \) — Oxide Capacitance (F)
\( V_{GS} \) — Gate Source Voltage (V)
\( V_T \) — Threshold Voltage (V)
\( V_{DS} \) — Drain Source Voltage (V)

Explanation: The equation integrates the voltage difference across the channel to determine the total current flow, accounting for the transistor's physical characteristics.

3. Importance of Drain Current Calculation

Details: Accurate drain current calculation is crucial for MOSFET circuit design, performance analysis, power consumption estimation, and ensuring proper transistor operation in various electronic applications.

4. Using the Calculator

Tips: Enter all parameters in appropriate units. Channel dimensions in meters, mobility in m²/V·s, capacitance in farads, and voltages in volts. All values must be positive except voltages which can be zero or positive.

5. Frequently Asked Questions (FAQ)

Q1: What is the significance of W/L ratio?
A: The W/L ratio determines the transistor's current handling capability. Higher W/L ratios allow more current flow for the same voltage conditions.

Q2: How does electron mobility affect drain current?
A: Higher electron mobility allows electrons to move more easily through the channel, resulting in higher drain current for the same voltage conditions.

Q3: What is the role of oxide capacitance?
A: Oxide capacitance represents the gate's ability to control the channel charge, directly influencing the amount of current that can flow through the transistor.

Q4: When is this equation valid?
A: This equation is valid for MOSFETs operating in the linear/triode region where VDS ≤ VGS - VT.

Q5: What happens if VDS > VGS - VT?
A: When VDS exceeds VGS - VT, the transistor enters saturation region and a different equation applies for drain current calculation.