CMOS analog integrated circuit (IC) design is a technology-dependent process. Analog design follows a process for which transistor sizing is necessary to achieve performance goals that are defined by a series of simulation tests. Both the design and the pedagogical processes make use of one or more algorithms in which a set of subcircuits are separately tested and then linked together into an integrated cell design, usually that of the 8-transistor operational transconductance amplifier (OTA). This paper identifies a technique that reduces much of the extra design overhead by framing the OTA as a single schematic who test configurations are controlled by a simulation version of a switch matrix. The switch matrix (1) links a set of independent sources and loads to the circuit under test and (2) reconfigures the test topology of the circuit. The new technique is of value to both the instruction process and the circuit designer since it is simple and direct. Given the simplicity it is also possible to compare effects of different technologies, usually by a collateral use of a spreadsheet utility and its graph capabilities. The student version of Cadence/ORCAD/pSPICE is the principal simulation design utility, with the Excel platform as a complementary utility.
The circuit simulation construct is a network of nodes interconnected by component devices that are responsive to the voltage and current stimuli applied as sources and signals. The component devices may be simple linear form or they may be non-linear devices, in which case they are usually of semiconductor origin. Each different type device owns a set of specific parameters that define its operation. The circuit simulator decomposes the circuit and ascertains the electrical facts of the circuit in the form of node voltages and branch currents, outcomes which are peculiar to the physical effects represented by the strengths of these device parameters and therefore of critical concern to a circuit designer.Semiconductor devices are generally devolved in the classroom by their device physics and the principles of operation that control the flow of electrons and holes. Basic first-order concepts lend themselves to mathematics that is reasonably tractable and can be readily developed by the versatility of the spreadsheet environment. However, for sub-micron devices, where the field effects are very intense, much of the first-order physics loses ground to second-order effects, most of which are abstract and often impenetrable to the circuit designer. And often any exposition of these second-order effects is a time-consuming burden to the instructor, whether for circuit design or for device physics. This paper identifies a technique that is invaluable to the circuit designer and/or semiconductor devices instructor by which the circuit simulations and the spreadsheet environments are integrated to resolve devices and/or circuit design questions. The environment can also be used for an empirical cross-coupling of device theory and circuit design. The student version of Cadence/ORCAD/pSPICE, which is the most common classroom circuit simulation platform, is the principal operational utility, with the Excel platform as the complementary spreadsheet utility.
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