kaylee wrote on Sep 12th, 2016, 12:32am:As you know, the gain constant of a transistor varies greatly even within the same batch of devices.
What do you mean with "gain constant of a transistor"?
In general, the solution to the problems you have mentioned is "negative feedback".
This applies to simple transistor gain stages as well as multi-stage amplifiers (in particular: opamps).
In this case, the gain is primarily determined by RATIOS of the parts values only - and ratios can be realized rather close to the desired values.