Patent ID: 6255872
Filing Date: 2001-07-03
Classification: H03L

Abstract:
A charge pump for a PLL, comprising:first and second constant current sources for generating constant currents;a first current mirror circuit for supplying a constant current having a value corresponding to the constant current generated by said first constant current source to an output terminal, said first current mirror circuit having a first transistor connected to said first constant current source and a second transistor connected to the output terminal;a second current mirror circuit for supplying a constant current having a value corresponding to the constant current generated by said second constant current source to the output terminal, said second current mirror circuit having a third transistor connected to said second constant current source and a fourth transistor connected to the output terminal;a first analog switch circuit which is connected between gates of said first and second transistors and turned on/off by a first control pulse;a second analog switch circuit which is connected between gates of said third and fourth transistors and turned on/off by a second control pulse;a first dummy transistor connected between said second transistor and the output terminal to operate in an opposite phase to a phase of said second transistor; anda second dummy transistor connected between the output terminal and said fourth transistor to operate in an opposite phase to a phase of said fourth transistor.