A new hybrid modeling method is proposed for the chip-package co-modeling and co-analysis. This method is designed to investigate the simultaneous switching noise (SSN) coupling paths and effects on the dc output voltage offset of the operational amplifier (OpAmp). It combines an analytical model of the circuit with a power distributed network (PDN) and interconnection models at the chip and package substrate. In order to validate the proposed model, CMOS OpAmp was fabricated using TSMC 0.25 mum. Then the dc output offset voltage of the OpAmp was measured by sweeping the SSN frequency from 10 MHz up to 3 GHz. It was successfully demonstrated that the experimental results are consistent with the predictions generated using the proposed model. We also confirmed that the dc offset voltage is strongly dependent on the SSN frequency and the PDN impedance profile of the chip-package hierarchical PDN. It shows the necessity for the chip-package co-modeling and simulation of the system-in-package designs.