Abstract: The specification describes techniques for isolating noisy subcircuits in integrated analog/digital devices. Isolation is obtained using a modification of triple well isolation wherein the deep isolation implant is restricted to the digital circuits only to prevent noise from the digital circuits from propagating to the analog sections through the buried implant. Resistor sections are also separated from the buried isolation implant.

Abstract: A method of shrinking an existing mixed signal IC containing analog and digital circuitry includes the step of first enlarging (growing) the analog circuitry by a first ratio, followed by the step of recombining the enlarged analog circuitry with the existing digital circuitry and, then, optically shrinking the recombined analog and digital circuits by a second ratio. In one embodiment the analog circuits are enlarged by a factor that will offset the subsequent optical shrink. As a result, the analog circuitry is essentially unchanged on silicon, while the digital circuitry will be smaller, thereby making the overall chip smaller.