Accurate extraction of simplified symbolic pole/zero expressions for large analog IC´s

We present the sifting approach and its implementation (AnalogSifter) for symbolic analysis and automatic extraction of symbolic pole and zero expressions for analog integrated circuits. Very compact symbolic expressions for the voltage gains of the two-stage CMOS, 741, and even larger operational amplifiers, were obtained in less than 40 CPU seconds on a SUN SPARCstation 2, and the simplified results match well with the exact numerical values up to the unity gain frequencies in both the magnitude and phase versus frequency plots. The symbolic pole and zero expressions are extracted accurately in the frequency range of interest. All pole and zero expressions may be extracted accurately in individual or clustered symbolic forms by scanning through different frequency ranges. The simplified symbolic pole and zero expressions we obtained in the example presented are within 3% of the exact values