| US 7,567,133 B2 | ||
| Phase-locked loop filter capacitance with a drag current | ||
| Randy Caplan, Hoschton, Ga. (US) | ||
| Assigned to MOSAID Technologies Corporation, Sunnyvale, Calif. (US) | ||
| Filed on Apr. 06, 2006, as Appl. No. 11/400,495. | ||
| Prior Publication US 2007/0247236 A1, Oct. 25, 2007 | ||
| Int. Cl. H03L 7/00 (2006.01) | ||
| U.S. Cl. 331—17 [331/16; 331/34] | 2 Claims |
| 1. Phase-locked loop circuitry comprising:
charge pump circuitry configured to generate a pump current based on a phase of an input signal;
loop filter circuitry configured to receive the charge pump current, the loop filter circuitry comprises a first capacitor
connected between a control voltage and ground, a first resistor connected between the control voltage and an integration
node, an operational amplifier having a positive terminal connected to the integration node, a second capacitor connected
between the integration node and ground, a second resistor between the control voltage and a negative terminal of the operation
amplifier, and a feedback link connecting an output of the operational amplifier to the negative terminal of the operational
amplifier; and
the first resistor, the second resistor, and the operational amplifier form drag current circuitry configured to generate
a drag current to draw charge in the opposite direction from the charging current from the first capacitor.
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