A variation tolerent reconfigurable time difference amplifier

In this paper, a variation tolerant reconfigurable time difference amplifier (TDA) is presented. The proposed time difference amplifier removes delay lines used in conventional calibration loop which are the most critical bottle-neck for achieving higher gain. A gated mutual exclusive (GMUTEX) circuit and a NAND based ring oscillator enable reconfigurable gain corresponding to an input code word. In addition, a time difference pre-amplifier is employed in phase frequency detector (PFD) of delay locked loop (DLL) to reduce its input phase offset. The proposed TDA is implemented and simulated in 90 nm CMOS, which shows 4 to 128 of reconfigurable gain within 6.3% of absolute gain error and 2.5% fluctuation under PVT variable condition.