Do power amplifiers that use a dynamic power supply operate in the active region, i.e. as a voltage controlled current source? or do they operate in the saturation region? and how do the current and voltage waveforms look like?

  • \$\begingroup\$ Are you talking about power amplifiers which cause their (+) and (-) voltage rails to track the output? (Switcher-type, adaptive rails, so to speak?) Or something else? \$\endgroup\$
    – jonk
    Sep 15, 2019 at 19:04
  • \$\begingroup\$ I am talking about power amplifiers where the supply voltage tracks the signal envelope for the purpose of achieving higher efficiency \$\endgroup\$
    – ali khalil
    Sep 15, 2019 at 19:06
  • \$\begingroup\$ It depends on the class of amplifier ! Class A, B, E , F etc affects efficiency. Conduction energy losses are defined by VIt. So short t , high f SMPS Class E amplifiers with LC filters are more efficient. Saturation efficiency region applies here when Ron is low compared to load Z (Ron/Z). Then switching losses are secondary. Higher class amplifiers tend to be more efficient. \$\endgroup\$ Sep 15, 2019 at 19:34
  • \$\begingroup\$ @alikhalil Then "class H." Got it. \$\endgroup\$
    – jonk
    Sep 15, 2019 at 20:45
  • \$\begingroup\$ It depends on the application - in RF you would look at efficiency vs. linearity. For a radar, a pulsed tone might run in full saturation whereas a com radio might run linear, or in some level of "backoff" such that a predistorter could do its job well. There are different orders of linearization that can be done, depending on application and desired result \$\endgroup\$
    – johnnymopo
    Sep 17, 2019 at 3:24

1 Answer 1


Only switched amplifiers (classes D, E, F, etc.) work in "saturation region". This kind of amplifiers doesn't switch the power supply rails because they are intrinsically efficient.

The only amplification classes that switch power rails or use some kind of dynamic power supply are class G and H, which are basically class AB amplifiers (thus working in "active region") with an "enhanced" power supply whose purpose is to achieve higher efficiencies (although typically lower than class D) while keeping distortion low.

Class G/H is typically used in audio application by manufacturers like NAD, Emotiva, Sunfire, etc.


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