Operational amplifiers used in PLL charge pump circuits
In this paper, the detailed design procedure for two operational amplifiers (OP-Amp) used in charge pumps (CP) is presented. Such procedure, which is from system-level specifications to circuit-level requirements, provides a general methodology for OP-Amp design in CP. The design was simulated in a 0.18µm CMOS process and occupies a layout area of about 200µm×100µm. The simulation results show that these two OP-Amps meets the specification under all CP's switching conditions, while drawing only 640µA from a 1.8V supply.