US Patent 7123085 Rail-to-rail charge pump with replica circuitry

The charge pump circuit includes: a charge pump output branch having a first transistor and a second transistor coupled in series; an output branch replica having a third transistor and a fourth transistor coupled in series; a feedback circuit coupled between the output branch and the output branch replica; a charge pump input circuit coupled to the charge pump output branch, and having first and second input branches; and an input circuit branch replica controlled by the feedback circuit and coupled to the charge pump input circuit.