Stupid Class D Questions


2006-09-18 4:50 pm

Sorry, i have been reading about class d amps but i am a lil confussed so im going to ask some very stupid noobish questions.

Firstly, is the power of the amp just dependant on the power supplied to the MOSFETs and the gain in the same way as a transistor?

Secondly, i am under the understanding that in a basic amp that one of the MOSFETs is on while the other is off? how is this possible when they share the same input?

Attached image is diagram of samples ive been learning from




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The power is dependent on the voltage the amp can output into a given load impedance, which will depend on the current capacity of the supply and the voltage rails. Obviously the current and voltage ratings of the output devices used must be able to take the conditions (safe operating area).

Gain is relevant only to determine for what input signal level the output voltage will (try to) be.

Yes only one output device is on at any one time, otherwise there would be a huge short circuit across the power supply. They don't quite share the same input, they will either be driven of opposite polarity signals or some kind of inverter before one of the devices, or in the case of the figure you attached one is n-channel and one is p-channel so they work in opposite polarity.