Thursday, July 23, 2015


Class D amplifiers are one most used and popular amplifier due to efficiency, theoretically class d amplifiers are 100 percent efficient. But this cannot be achieved practically as no device is 100 percent efficient. Though class d amplifiers reach more than 90% of efficiency if designed very carefully.
Understanding class d amplifiers are very much simple if you are familiar with the Switch mode power supply or commonly called SMPS or switching supply.
Input for the class d amplifier is first modulated either using Pulse Width Modulation ie PWM or sigma Delta modulates. Order of modulation starts generally from two and can reach as higher as 5 or even higher.
Class d amplifier can either be half bridged which requires dual power supply or full bridge and can be powers with single power supply. The problem with full bridge is that it requires more hardware or switching MOSFET which decrease its efficiency.
Another thing that make the class d amplifiers better is bridge tied load configuration or bridging multiple amplifiers so that its output power can be doubled. In bridge tied load configuration two half bridge amplifiers as bridged so that its output is doubled and the power for this configuration should be dual Power supply.
What is happening in class d amp is the modulated PWM is turning on and off the MOSFET bridge. during this MOSFETs ate switched on alternately. But if two of the MOSFETs on high side is turned on a pop sound can be created which may be very annoying. Also if there is delay between the next switching sequence the there might be dead sound between the sound.