Whenever large amplifier with very good impedance matching is required, a signal stage amplifier circuit will not able to amplify the signal to a large extent.
Thus, a number of stages are required for amplification, for this output of the stage is connected to the input of the second stage, this is called as cascade system or multi-stage system.
The connection of output first stage to the input second stage is called coupling.
In case of a multistage system, the very good coupling is very essential systems, very good coupling is very essential or else there will be a large number of losses at the output.
