Mixed Mode Simulation

The purpose of the mixed-mode simulation work at Stanford is to provide a mechanism to include complex devices in SPICE where compact models may be inadequate. Such devices include GaAs MESFET's, heterostructure devices, short channel MOSFET's, and optical devices. SPICE provides an industry standard for circuit simulation upon which the numerical device model is added. Given the versatility of SPICE, mixed-mode provides a means to consolidate other projects in the TCAD group. Parasitic extractions from layout can be coupled with device cross sections created in the virtual factory and simulated in a mixed-mode environment before committing to the manufacturing line.

Unlike the current mixed-mode simulators on the market, Stanford has taken the approach of a loosely coupled algorithm. As a result, any device simulator may be added into the mixed-mode environment with the addition of a few routines and a couple of small changes to the device simulator. In addition, each numerical device in the circuit may be simulated with a different simulator which leads to more robust solutions since the most accurate simulator for the device may be used. Hence, the main advantage of the loosely coupled algorithm at Stanford is the modularity. This same modularity leads to an increases in simulation time since the circuit and device responses are solved with two separate sets of iterations.

For more information on mixed-mode, please examine the pages from a computer demonstration at the 1994 IEDM conference or contact Francis.

Francis Rotella (rotella@gloworm.Stanford.EDU)
Applied Electronics Lab 231E
Integrated Circuits Laboratory
Stanford University
Stanford, CA 94305-4055