Fully Differential Amplifier Gain Calculator

Fully Differential Amplifier Gain Equation:

\[ Gain = \frac{R_f}{R_{in}} \times \left(1 + \frac{2 R_{in}}{R_{cm}}\right) \]

Gain:

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1. What is Fully Differential Amplifier Gain?

The fully differential amplifier gain represents the amplification factor of a differential amplifier circuit that processes both differential and common-mode signals. It provides balanced output signals with improved noise rejection and signal integrity.

2. How Does the Calculator Work?

The calculator uses the fully differential amplifier gain equation:

\[ Gain = \frac{R_f}{R_{in}} \times \left(1 + \frac{2 R_{in}}{R_{cm}}\right) \]

Where:

\( R_f \) — Feedback resistance (Ω)
\( R_{in} \) — Input resistance (Ω)
\( R_{cm} \) — Common-mode resistance (Ω)
\( Gain \) — Amplification factor (dimensionless)

Explanation: The equation calculates the overall gain by combining the differential gain component (R_f/R_in) with the common-mode gain enhancement factor (1 + 2R_in/R_cm).

3. Importance of Gain Calculation

Details: Accurate gain calculation is crucial for designing differential amplifier circuits, ensuring proper signal amplification, maintaining common-mode rejection, and optimizing circuit performance in applications like instrumentation and communication systems.

4. Using the Calculator

Tips: Enter all resistance values in ohms (Ω). Ensure all values are positive and non-zero. The calculator will compute the dimensionless gain value based on the provided resistance parameters.

5. Frequently Asked Questions (FAQ)

Q1: What is the advantage of fully differential amplifiers?
A: Fully differential amplifiers provide better noise immunity, reduced even-order harmonics, and improved common-mode rejection compared to single-ended amplifiers.

Q2: How does R_cm affect the gain?
A: Lower R_cm values increase the gain enhancement factor, while higher R_cm values make the gain approach the basic differential gain (R_f/R_in).

Q3: What are typical resistance values used?
A: Typical values range from hundreds of ohms to tens of kilohms, depending on the application requirements and amplifier specifications.

Q4: Can this calculator be used for single-ended amplifiers?
A: No, this equation is specifically for fully differential amplifier configurations. Single-ended amplifiers use different gain formulas.

Q5: What if R_cm approaches infinity?
A: As R_cm becomes very large, the gain simplifies to R_f/R_in, which is the standard differential gain without common-mode enhancement.