Re: bandwidth of am
For amplifiers the gain and bandwidth product remains constant.As the gain increases (due to number of stages) the bandwidth decreases.
suppose there are n identical amplifier stages connected in cascade each with gain A.And also let us take for simplicity the upper cut-off frequency be fh anf lower cut-off fl be≈0.then bandwidth b≈fh.
The frequency dependence of amplifier gain is given by
A(f)=A/√(1+(f/fh)²)-----------(1)
Gain of the multi stage amplifier will be then
A(total)=A×A×A................(n times)
A(total)=A^n---------------------(2)
let upper cutoff of this multi stage amplifier be F.Then
A(total)/√(1+(f/F)²)=(A/√(1+(f/fh)²))^n
simplifying this equation
F=fh×(2^1/n-1)^0.5 where fh is the bandwidth of single stage amplifier
I think this might be of help to you.
Regards.