I have had an awesome idea for an amplifier that has no analog amplification and uses only switching waveforms and therefore is very efficient!
Diagram:
usb uart > I2S > fpga based delta sigma modulator > bitstream > gate drive > power fets
The delta sigma modulator will probably initially take 24bit input with unused LSB's dithered using a pseudo random generator. The modulator will initially be of second order and operate with a sample rate of 3MHz. This is to simplify the mathematics of the design as 2nd order should be stable! also sample rate is ultimately constrained by gate capacitance of the power fets.
To verify that this will work I shall code a simulation of the delta sigma modulator in PASCAL. As a digital circuit will behave ideally I can also do some fft on a suitably low pass filtered version of the bitsteam output and check that performance is adequate!
3 comments:
You are aware this already exists? Look up D-Class Amplifiers on Wikipedia.
the class D amps usualy use PWM and take an analog input only. As far as I am aware there isn't an amp that takes usb input and directly converts it to a delta sigma bitstream. IF there is I don't care regardless as doing it this way will allow loads of cool features like controlling a wall sized FFT display. Also it's a good excuse to learn some VHDL :D
ok it already exists but I don't care: http://focus.ti.com/docs/prod/folders/print/tas5706.html but that's not the fun way to do things!
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