A differential amplifier common mode gain is a measurement of the amplifier's ability to reject common mode signals, which are signals that are present on both of its input terminals. It is a ratio of the output voltage to the common mode voltage at the input.
The common mode gain is important because it determines the amplifier's ability to distinguish between the desired signal and any unwanted noise or interference that may be present on both input terminals. A higher common mode gain means better rejection of common mode signals, resulting in a cleaner output signal.
The common mode gain is calculated by dividing the output voltage by the common mode voltage at the input. It is usually expressed in decibels (dB) and can be calculated using the formula: CM Gain = 20log(Vout/Vcm).
The common mode gain of a differential amplifier can be affected by various factors such as the amplifier's design, component tolerances, and external noise sources. It can also be affected by the amplifier's power supply voltage and temperature.
The common mode gain can be improved in a differential amplifier by using high-quality components, minimizing external noise sources, and implementing proper shielding and grounding techniques. Additionally, using a higher power supply voltage and maintaining a stable temperature can also help improve the common mode gain.