A global reference-circuit (RC), which means one RC is shared with many sensing circuits (SC), is being considered for high-bandwidth STT-RAMs because of the low power consumption and small area characteristic. However, using the global RC for high-bandwidth STT-RAMs causes a droop effect and coupling noise effect, leading to the significant performance degradation. Thus, the validity of using the global RC should be identified. In this paper, the local RC and various global RCs are introduced, and compared in aspects of area, sensing time, and power consumption. By classification of the merits and demerits of various RCs, we present the following requirements of proper RC for high-bandwidth STT-RAMs: 1) small area, 2) no performance degradation, 3) low power consumption, and 4) process variation tolerant reference signal generation.