What term refers to the ratio of an amplifier's output to input signal?

The term referring to the ratio of an amplifier's output to input signal is "System Gain." System Gain is a critical concept in electronics and signal processing, as it quantifies how much an amplifier increases the strength of an input signal. This ratio is typically expressed in decibels (dB), which helps in comparing different amplifying systems or components in terms of their efficiency in amplifying signals. Understanding system gain is essential for professionals in fields ranging from audio engineering to biomedical instrumentation, as it affects overall system performance.

The other options, while related in context, do not accurately describe this specific relationship. Input Ratio might imply a consideration of input levels but does not encompass the output. Signal Enhancement suggests improvements in signal characteristics without reference to the quantitative relationship between input and output. Output Ratio could be misleading, as it might imply a comparison to some other factor rather than a direct ratio of input to output, not specifically acknowledging the amplifier's function.