Current In Common-Mode Rejection Of MOSFET Calculator

Formula Used:

\[ I_t = \frac{V_{icm}}{(1/g_m) + (2 \times R_{out})} \]

Total Current (I_t):

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1. What is the Current in Common-Mode Rejection of MOSFET?

The current in common-mode rejection of MOSFET refers to the total current flowing in a differential amplifier circuit when a common-mode signal is applied. It's an important parameter in analyzing the common-mode rejection ratio (CMRR) of MOSFET-based differential amplifiers.

2. How Does the Calculator Work?

The calculator uses the formula:

\[ I_t = \frac{V_{icm}}{(1/g_m) + (2 \times R_{out})} \]

Where:

\( I_t \) — Total current (A)
\( V_{icm} \) — Incremental common-mode signal (V)
\( g_m \) — Transconductance (S)
\( R_{out} \) — Output resistance (Ω)

Explanation: This formula calculates the total current in a MOSFET differential amplifier when a common-mode signal is applied, taking into account the device's transconductance and output resistance.

3. Importance of Current Calculation

Details: Calculating the current in common-mode rejection is crucial for designing differential amplifiers with high common-mode rejection ratio (CMRR), which is essential for rejecting noise and interference in electronic circuits.

4. Using the Calculator

Tips: Enter the incremental common-mode signal in volts, transconductance in siemens, and output resistance in ohms. All values must be positive and greater than zero.

5. Frequently Asked Questions (FAQ)

Q1: What is common-mode rejection ratio (CMRR)?
A: CMRR is a measure of a differential amplifier's ability to reject common-mode signals (signals that appear simultaneously and in-phase on both inputs) while amplifying differential signals.

Q2: Why is transconductance important in MOSFET circuits?
A: Transconductance (g_m) represents how effectively a MOSFET converts input voltage changes into output current changes, making it a key parameter in amplifier design.

Q3: What affects the output resistance in MOSFET circuits?
A: Output resistance is influenced by the MOSFET's channel length modulation effect and the circuit configuration. Longer channel lengths typically result in higher output resistance.

Q4: How does this calculation relate to differential amplifier performance?
A: The current calculation helps determine how much common-mode signal gets converted to output current, which directly affects the amplifier's common-mode rejection capability.

Q5: Are there practical limitations to this formula?
A: This formula provides an idealized calculation and may need adjustment for real-world factors such as temperature variations, device mismatches, and parasitic capacitances.