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Class D amplifier: The current-switched class D amplifier with transformers
Switch the constant current IDC rather than a constant voltage
Like class B but!!
 CB1 => RFC so the centre tap carries a constant current IDC
 L0C0 => short harmonic currents
 Each primary winding carries half-sine collector voltages
The class D amplifier with reactive load
The reactance load causes phase
shift between iO, vR
 Freewheel diode D1 & D2
All parasitic capacitance Cs at
the switching node A is
periodically charged and
discharged, causing additional
power loss that cannot be
avoided
 Q2 is forced to
source a
current instead
of sinking it
 Place external
diodes (at
horizontal
FET’s)
Output current
divided by
Charge left on CS is dissipated
Class F amplifier with LC circuits
Or biharmonic, poly-harmonic, class CD, class
C with increased efficiency, single-ended class
D, mutli-resonator
Operates at very high frequencies
 Add one or more harmonic frequencies
Current source during 180°
For a given VOM the min. peak amplitude (=
maximal flattening) when VCM3 = VOM / 9