Hi,
A High gain in an opamp means that this circuit can amplify smaller
signals than other one with less gain. In other words, High gains
in an opamp limits the amplitud for the input signal.
Look the following simple example:
1. I have an opamp with Gain=100V/V and a Voltage output swing = 1V.
Then, I can put in the input, a signal amplitud as high as 1/100=10mV.
2. Now, the opamp's gain is increased to 20000V/V with the same topology
(probably because I optimized my design
). In this case, for the
Voltage output swing of 1V, the maximum amplitud for the input signal
is only 50uV!. If we have two stages, we can allocated a gain of 500V/V
for the first stage and 40V/V for the second. Then, the maximum signal
amplitud at the input of the second stage is (50uV)x(500V/V)=25mV.
This value probably will be a small variation around the DC bias
of the second stage.
This example show us, that we must be careful with the amplitud for the input
signal in order to maintain the linearity of the system.
Regards,
PD: Excuse me for my bad english