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Common-Mode Gain Of Controlled Source Transistor Calculator

Common Mode Gain Equation:

\[ A_{cm} = 20 \times \log_{10}\left(\frac{V_{ss}}{V_{is}}\right) \]

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1. What is Common Mode Gain?

Common Mode Gain (Acm) is typically much smaller than the differential gain. Acm is the gain given to a voltage that appears on both input terminals with respect to the ground in controlled source transistor circuits.

2. How Does the Calculator Work?

The calculator uses the Common Mode Gain equation:

\[ A_{cm} = 20 \times \log_{10}\left(\frac{V_{ss}}{V_{is}}\right) \]

Where:

Explanation: The equation calculates the common mode gain in decibels by taking the ratio of small signal to differential input signal and applying a logarithmic scale with a multiplier of 20.

3. Importance of Common Mode Gain Calculation

Details: Accurate common mode gain calculation is crucial for analyzing the performance of differential amplifiers, determining common mode rejection ratio (CMRR), and ensuring proper signal processing in electronic circuits.

4. Using the Calculator

Tips: Enter small signal voltage and differential input signal voltage in volts. Both values must be positive and greater than zero for accurate calculation.

5. Frequently Asked Questions (FAQ)

Q1: What is the significance of the 20 multiplier in the formula?
A: The multiplier of 20 is used to convert the voltage ratio to decibels, which is the standard unit for gain measurements in electronic systems.

Q2: What are typical values for common mode gain?
A: Common mode gain values are typically much smaller than differential gains, often ranging from a few decibels to negative values, indicating signal attenuation.

Q3: How does common mode gain affect circuit performance?
A: Lower common mode gain values indicate better common mode rejection, which is desirable in differential amplifiers to suppress noise and interference that appears equally on both inputs.

Q4: What is the relationship between common mode gain and CMRR?
A: Common Mode Rejection Ratio (CMRR) is calculated as the ratio of differential gain to common mode gain. A higher CMRR indicates better rejection of common mode signals.

Q5: When should this calculation be used?
A: This calculation is essential when designing or analyzing differential amplifiers, operational amplifiers, and other circuits where common mode signal rejection is important for proper operation.

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