Output Voltage at Drain Q2 of MOSFET given Common-Mode Signal Calculator

Formula Used:

\[ V_{o2} = -\frac{R_{out}}{(\frac{1}{g_m}) + 2 \times R_{out}} \times V_{cin} \]

Output Voltage at Drain Q2:

Unit Converter ▲

Unit Converter ▼

From:	To:

1. What is Output Voltage at Drain Q2?

The output voltage at drain Q2 represents the voltage measured at the drain terminal of transistor Q2 in a differential amplifier circuit when a common-mode input signal is applied. This measurement is crucial for analyzing the performance and common-mode rejection characteristics of differential amplifiers.

2. How Does the Calculator Work?

The calculator uses the following formula:

\[ V_{o2} = -\frac{R_{out}}{(\frac{1}{g_m}) + 2 \times R_{out}} \times V_{cin} \]

Where:

\( V_{o2} \) — Output voltage at drain Q2 (V)
\( R_{out} \) — Output resistance (Ω)
\( g_m \) — Transconductance (S)
\( V_{cin} \) — Common mode input signal (V)

Explanation: This formula calculates the output voltage at the drain of transistor Q2 in a differential pair configuration, taking into account the output resistance, transconductance, and common-mode input signal.

3. Importance of Output Voltage Calculation

Details: Calculating the output voltage at drain Q2 is essential for understanding the common-mode rejection ratio (CMRR) of differential amplifiers, analyzing circuit stability, and designing balanced amplifier configurations for noise reduction and signal integrity.

4. Using the Calculator

Tips: Enter output resistance in ohms, transconductance in siemens, and common-mode input signal in volts. All values must be positive (output resistance > 0, transconductance > 0).

5. Frequently Asked Questions (FAQ)

Q1: What is the significance of the negative sign in the formula?
A: The negative sign indicates that the output voltage at drain Q2 is inverted relative to the common-mode input signal, which is characteristic of differential amplifier operation.

Q2: How does transconductance affect the output voltage?
A: Higher transconductance values generally result in smaller output voltage magnitudes for a given common-mode input signal, as the denominator term (1/gm) becomes smaller.

Q3: What is the typical range for output resistance in MOSFET circuits?
A: Output resistance values typically range from hundreds of ohms to several kilo-ohms, depending on the specific MOSFET configuration and biasing conditions.

Q4: Why is common-mode signal analysis important?
A: Common-mode analysis helps determine how well a differential amplifier rejects unwanted signals that appear equally on both inputs, which is crucial for noise immunity in electronic systems.

Q5: Can this formula be used for bipolar junction transistors (BJTs)?
A: While the concept is similar, BJTs have different characteristics and would require modified formulas that account for their specific parameters and operating principles.