High‐frequency simulation of the 600‐MHz wideband‐amplifier IC

Abstract

As analog ICs are finding use in a higher frequency band, a circuit simulator which is accurate in a high‐frequency region beyond 100 MHz becomes necessary. In this paper, a 600‐MHz wideband amplifier IC and its bipolar transistors and resistors are fabricated on an identical chip. By evaluating their S parameters, the accuracy of the device model was verified for simulation of analog IC at frequencies above 100 MHz. First, the parasitics of packages were modeled to verify the accuracy of the device model. It is shown that consideration of the resistance of pads is necessary. Next, the accuracy of the hybrid π model used widely as a high‐frequency model of the bipolar transistor was verified with the S parameters. It is found that the present form has poor accuracy at frequencies above 100 MHz. It is shown also that the IC structure of the transistor must be considered to improve the accuracy. Significant improvement of accuracy can be obtained if an extended model is introduced in which the separations of the base‐collector capacitance and the base‐emitter capacitance and the introduction of substrate resistance are included. Finally, by means of this extended model, a good high‐frequency simulation of a 600‐MHz wideband amplifier IC is realized.