71.2.4. Dangers of Common Mode Signals

In case if you have a situation like this. Suppose your main signal is this one the violet colour one, but then you do have a lot of disturbance getting represented by this blue signal and in case if you want to really find the find out this signal and if you extract this remove the noise part, the blue part then you can take help from this differential amplifier, how will you tell while you are feeding the signal it is having different response to the differential component and the common mode component.

This chunk discusses the scenario where a desired signal is mixed with noise. The example describes two signals: one (the main signal, in violet) that you want to capture, and another (the common mode noise, in blue) that you want to eliminate. A differential amplifier can differentiate between these two types of signals and amplify only the desired signal, while minimizing the noise. This is critical for maintaining signal integrity in many electronic applications, especially in environments with a lot of electrical interference.

Imagine trying to listen to your favorite song on the radio while there is a loud crowd cheering nearby. The song you want to hear represents the main signal, and the crowd noise is the common mode signal. A good radio (like a differential amplifier) can pick and amplify the song, allowing you to filter out much of the crowd noise, so you can enjoy your music without distractions.

So, if I say that it is a differential mode gain ad it is said high. So, if this is say high quote and unquote high and the common mode gain ac if I say it is having low value then at the output whatever the v you will get will be amplified. The amplified version of this signal and then if it is low common mode gain, it is low then this blue colour part it will be also coming here as common mode, but its strength it will be less.

This chunk explains the importance of differential and common mode gains in a differential amplifier. Differential gain (ad) should be high to amplify the desired signal effectively, while common mode gain (ac) should be low to ensure that the unwanted noise does not significantly affect the output. If the differential mode gain is high and the common mode gain is low, the desired signal can be amplified much more than the noise, ensuring a cleaner output.

Consider a teacher in a noisy classroom. The teacher's voice represents the differential signal, and the noise from the students represents the common mode signal. If the teacher speaks loudly (high differential gain), students' background chatter (low common mode gain) won’t distract from the lesson. In a good learning environment, it’s essential that the teacher can be heard despite the noise.

So, the summary is that this is most dangerous thing. So, definitely we want both A_c_d and A should be low. So, priority wise; however, this is having highest priority to make it as small as possible and then probably this one and then the third one is this A.

This chunk emphasizes the dangers of having a high common mode gain in differential amplifiers. If the common mode gain is high, it can allow unwanted noise to be amplified along with the desired signal, defeating the purpose of using a differential amplifier in the first place. Therefore, reducing common mode gain is critical. Maintaining low values for both common mode gain and the common mode to differential gain ensures that the differential amplifier performs optimally.

Think of a strong wind blowing through trees during a storm. If the trees are not strong enough (high common mode gain), they will sway dangerously (let unwanted signals through), while the gentle rain (desired signal) might not be able to reach the ground as effectively. We want our trees (amplifiers) to withstand the storm well, ensuring that only the beneficial rain gets through unimpeded.

In fact, we have said that this part particularly common mode to differential mode gain should be as small as possible otherwise it may create a problem and of course, the differential mode gain it should be as high as possible.

This chunk underscores that keeping common mode to differential mode gain small is essential to prevent common mode signals from interfering with the differential signal. If common mode signals accidentally get converted to differential mode, they may be incorrectly amplified, leading to signal distortion. Hence, ensuring a low common mode to differential mode conversion helps maintain the reliability and integrity of the output signal.

Imagine a mail sorting system where letters (signals) are sorted into specific bins. If a mail sorter incorrectly puts letters meant for one bin into another (common mode signals converting into differential), the recipients (output signal) could receive the wrong mail. The goal is to make sure every letter is sorted accurately without error to maintain efficient communication.

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