text: Switched mode amplifiers These nonlinear amplifiers have much higher efficiencies than linear amps, and are used where the power saving justifies the extra complexity. Class-D amplifiers are the main example of this type of amplification.
  Negative resistance amplifier
  Negative Resistance Amplifier is a type of Regenerative Amplifier that can use the feedback between the transistor's source and gate to transform a capacitive impedance on the transistor's source to a negative resistance on its gate. Compared to other types of amplifiers, this "negative resistance amplifier" will require only a tiny amount of power to achieve very high gain, maintaining a good noise figure at the same time.
  Applications
  Video amplifiers
  Video amplifiers are designed to process video signals and have varying bandwidths depending on whether the video signal is for SDTV, EDTV, HDTV 720p or 1080i/p etc.. The specification of the bandwidth itself depends on what kind of filter is used—and at which point ( or  for example) the bandwidth is measured. Certain requirements for step response and overshoot are necessary for an acceptable TV image.
  Microwave amplifiers
  Traveling wave tube amplifiers (TWTAs) are used for high power amplification at low microwave frequencies. They typically can amplify across a broad spectrum of frequencies; however, they are usually not as tunable as klystrons.