Re: how to design amplifer
mydreamhouse said:
as i know there are two different way to design amplifer, one begins with gain,power assumption,and other is the way of berkely,which use DR and phase margin. how to select the way ?
Power is not the critical design concern; if it is, I would like to say current is more important.
The first thing to find a solution to opamp design is the structure defining and process choosing according to your requirements. If high speed, using one stage cascode; if high gain, use two stages; if both using gain booster; and so on.
Once the structure and process is defined, current allocation to each branch is the must, which is to minimize the system offset. Large current can achieve high speed, and low current is good for high gain.
noise the concerned then, because it is mainly caused by input pairs, you do not require to change a lot of your design when lowering your noise.
phase margin is not more related to the compensation and parasitic capacitance. study it can improve the phase margin.
Basically, arbitaty high current can help to meet all requirements you want. If you need low current and very high performance with fixed process, a new structure should be invented, so you can be patented.
So, process and current would be the breakpoint.