Charge Pump Using Gain-Boosting and Positive Feedback Techniques in 180-nm Digital CMOS Process

Abstract

The charge pump (CP) circuit is an essential element in a delay-locked loop (DLL). This paper proposes a new CP using gain-boosting technique. Two possible solutions for gain-boosting circuit implementation are presented. One solution is based on common-source amplifier. In another solution, positive feedback method is employed at the output stage to increase the output resistance of the amplifier. Therefore, DC-gain of the amplifier is improved. In addition, nonlinear current mirror is employed in which the gain is dependent to the input current. To evaluate the performance of the proposed CPs, simulations are done in a 0.18 μm CMOS process with the supply voltage of 1.8 V. The simulation results indicate that the proposed CPs can obtain good current matching characteristics in the low power applications. The mismatch between up and down CP currents is less than 1%.