Application of Folded Cascode-Based Gain-Boosting Circuit in Declining the Current Mismatch Characteristics

In this study, a folded cascode-based gain-boosting circuit (FCB-GBC) is introduced for CP to decrease the variation of Up/Down current with respect to the output voltage variation via increasing the CP output resistance. In the phase-locked loop (PLL), the phase offset is generated by current mismatch of charge pump (CP), resulted in increasing the spurs of the PLL's output signal. The proposed structure improves the variation of Up and Down currents in the fluctuation of CP output voltage considerably. The proposed FCB-GBC does not require operational amplifier, extra cascode devices, and compensators, while results in significant improvement in current mismatch modification. The simulation results of the proposed CP indicates the current mismatch characteristics of lower than 0.1 % and 0.6% for the Up/Down current difference over the CP output voltages ranges of 0.5-1.25 V and 0.4-1.3 V, respectively, in 0.18µm TSMC CMOS technology.