text: Amplifiers designed to attach to a transmission line at input and output, especially RF amplifiers, do not fit into this classification approach.  Rather than dealing with voltage or current individually, they ideally couple with an input or output impedance matched to the transmission line impedance, that is, match ratios of voltage to current.  Many real RF amplifiers come close to this ideal.  Although, for a given appropriate source and load impedance, RF amplifiers can be characterized as amplifying voltage or current, they fundamentally are amplifying power.
  Properties
  Amplifier properties are given by parameters that include:
  Gain, the ratio between the magnitude of output and input signals
  Bandwidth, the width of the useful frequency range
  Efficiency, the ratio between the power of the output and total power consumption
  Linearity, the extent to which the proportion between input and output amplitude is the same for high amplitude and low amplitude input
  Noise, a measure of undesired noise mixed into the output
  Output dynamic range, the ratio of the largest and the smallest useful output levels
  Slew rate, the maximum rate of change of the output
  Rise time, settling time, ringing and overshoot that characterize the step response
  Stability, the ability to avoid self-oscillation