This paper reports a new 0.5V supply high resolution CMOS comparator suitable for biosensor applications. The comparator uses a body-driven PMOS-diode differential pair and compensates for differential body-input referred offset-voltage through single-ended sampled-data pre-amplification. Extensive simulations were carried out using a 0.13?m IBM CMOS process technology. The comparator has a differential input overdrive resolution of under 2mV and a response time of around 0.1?sec which is scalable. The static power dissipation by the comparator from the 0.5V supply is under 5?W making it extremely suitable for implantable biosensor devices. In addition, the comparator uses a Truly Single Phase Clock (TSPC) for the sampled data operations, thus simplifying dynamic timing requirements.