Where does this come from ? How do I get this in real design? suppose I have a small sine voltage, how do I add common mode voltage to that so my amplifier can actually operate.
Can I use a voltage divider to get a dc voltage down to like 0.6V and connect to both input of op amp as common mode input?
.......... suppose I have a small sine voltage, how do I add common mode voltage to that so my amplifier can actually operate. Can I use a voltage divider to get a dc voltage down to like 0.6V and connect to both input of op amp as common mode input?
You have to give a certain common mode input voltage(DC) on which the differential signal(ac) is superimposed.
This common mode input voltage acts as the bias voltage for the transistors inorder to work at the operating point. I hope you know the importance of bias voltage.
Hence it is important to give a common mode input voltage as a bias voltage.. although the differential amplifier amplifies only the differential(ac) signal and rejects the common mode signal.
I assume you are asking how do I bias using a single supply.. Correct me If I am wrong..
You have various methods for biasing.... voltage divider, self-bias etc.