An 
amplifier having an active and passive 
gain stage connect to a load for driving a load according to a 
system analog input. A first embodiment of the 
amplifier in accordance with the present invention includes a 
logic network connected between a 
comparator network and a switching 
system, wherein the 
comparator network connects to the passive 
gain stage. Specifically, the active 
gain stage may include an 
active filter connected to receive an analog or 
digital input and provide a difference between the analog or 
digital input and the feedback 
signal relative to the 
gain factor of a gain unit connected to the 
active filter. The passive 
gain stage includes a passive filter. The 
logic network generates at least one 
switching signal which controls the switching 
system that includes at least one switching device to selectively provide power to the load. An output 
signal from the switching system provides output for the 
amplifier and is fed back to the active 
gain stage. In another embodiment, the output is a two-level 
signal and the passive and active filters are second order low pass filters, where the 
gain factor is about 25 or more. In yet another embodiment, the 
gain factor is approximately 250. Moreover, the amplifier may include a digital 
delta-sigma modulator connected to supply a two level input.