Can a MOSFET h-bridge class-D amplifier be used as a digital-to-analog converter?
Consider how difficult it is to produce an accurate, fast-moving analogue value from PWM. Compare this to a 16-bit serial DAC. If the 16-bit DAC were clocked at 50 MHz (serial SPI for instance) then there would be an "analogue" update of an accurate value every 0.32 us (Equivalent to 3.125 MHz)

To get 16-bit accuracy from PWM requires that the PWM duty cycle is controllable to a 1 in 65536 resolution. So, with a base frequency of 3.125 MHz, you need a clock that is 65536 times faster than this to control duty cycle. That sounds like 204.8 GHz to me.

Even then one cycle of PWM (0.32 us) is barely enough to turn a PWM signal into a valid 16-bit accurate analogue signal.


  But how common are they for high frequency D/A conversion


Do you see the problem?