How can I measure FOM(figure of merit) of an operational amplifier? There are so many parameters, how can I decide which formula to use while calculating FOM?
Electrical – Figure of merit of Operational amplifier
analogcircuit-designintegrated-circuitoperational-amplifier
Best Answer
A Figure of Merit severely depends on the situation. In commercial applications I can only see limited use for it, but for R&D purposes it does have its advantages.
The idea is that you try to isolate anything that is not dependent on factors common to all amplifiers. For example, in CMOS design, driving a 1pF capacitive load can be made faster much easier than a 10pF capacitive load. It makes sense to have a FOM in this case that does not depend on the output capacitance.
The most commonly adopted FOM's that I have seen are something along the lines of
$$FOM = \frac{GBW\cdot C_L}{P}$$ or $$FOM = \frac{GBW\cdot C_L}{I_{BIAS}}$$
But depending on the situation, other factors can be included as well. To find the FOM, you measure all the parameters in the equation and calculate the FOM manually.