http://www.loc.gov/mods/v3 http://www.loc.gov/standards/mods/v3/mods-3-2.xsd
Analog involves real world parameters, real world measurements. The signal path from beginning to end operates on the input whether for amplication, detection, conversation or any other function. The way we achive that operation is important. Since it is the circuitry that operates on an analog signal, the circuitry leaves its stamp on the output signal. Real world degradation of analog signal is easy to assess. Noise can increase, distortion can occur, voltage accuracy can worsen, and drifts can be introduced. Since the impact on the signal is a fuction of the circuitry used to operate on the signal, optimizing an analog circuit is very important.