Graph illustrating the concept of amplification.  It shows the output vo(t){\displaystyle v_{o}(t)\,} of an ideal linear amplifier given an arbitrary time-varying signal vi(t){\displaystyle v_{i}(t)\,} as input.  Amplification means increasing the amplitude (voltage or current) of an arbitrary electrical signal by a uniform amount, as illustrated here.  The amplifier in this example has a gain of 2; that is vo(t)=2vi(t){\displaystyle v_{o}(t)=2v_{i}(t)\,}
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