A novel quantum-MOS sense amplifier circuit consisting of resonant tunneling diodes (RTD's) as pull-up devices and NMOS transistors is discussed in this paper. Compared to the conventional sense amplifier circuits using CMOS technology, the proposed QMOS sense amplifier exhibits about 20% higher sensing speed. The cross-coupled QMOS latch, which is at the heart of the sense amplifier circuit, has meta-stable and unstable states which are closely related to the I-V characteristics of the RTD's. The stability analysis has been made by using phase-plot diagram and how RTD parameters relate to circuit speed and robustness of the sense amplifier has been discussed.