Class D amplifiers, often incorrectly called digital amplifiers, are simply a continuation of the A, B, and C classification. A Class D is basically an audio modulated, PWM utilizing a saturated output stage such as those using power FETs. It is an amplifier where the output transistors are switched in the fully ON or OFF region. The outputs are continuously switched from one rail to the other at a high frequency. High efficiencies of up to 95% can be achieved, which leads to more compact products by eliminating the large heatsink which dissipates much of the usual heat. The one drawback of Class D amp is the high level of EMI emissions.