Of the reported modulation techniques for Class D amplifiers (CDAs), CDAs based on Bang-Bang control modulation are arguably the most advantageous in terms of power-efficiency for low-power power-critical applications. To date, only single-ended and 2-state Bang-Bang control CDAs have been reported, and are hence disadvantageous because they require a bulky and costly output lowpass filter. In this paper, we propose the first-ever 3-state Bang-Bang control filterless CDA applicable to regular-power and ultra-low-power applications. Compared to other filterless 3-state CDAs, the proposed filterless 3-state Bang-Bang control CDA features the simplest hardware and the highest power-efficiency, but with somewhat compromised fidelity. Nevertheless, the fidelity thereto is sufficient for typical ultra-low-power applications such as low-to-mid performance wearable devices.