SPICE simulators

Since its introduction in 1971, SPICE (Simulation Program with Integrated Circuit Emphasis) has become the most popular analog simulation tool in use today. In the last 15 years, we have seen explosive growth in the use of SPICE, with the addition of Berkeley SPICE 3 enhancements, and support for C code model and mixed-mode simulation using XSPICE (Cox et al. 1992, Kielkowski 1994).We have also seen many new companies emerge as developers of SPICE-based simulation tools, most of which are currently available for the PC platform. 

Each vendor of SPICE simulation software has added features such as Monte Carlo analysis, schematic entry, and post simulation waveform processing, as well as extensive model libraries. In most cases, the manufacturers have modified the algorithms for controlling convergence and have added new parameters or syntax for component models. As a result, each electronic design automaton (EDA) tool vendor has the basic Berkeley SPICE 2 features and a unique set of capabilities and performance enhancements. 

Still, there are limitations to the capabilities of SPICE and similar circuit simulators. While the sophistication of simulation increases, the hardware breadboard will still remain a necessary step in the design process. This book will aid the engineer in using SPICE simulation as a very powerful tool in the design process. 

Schematic capture Text editor SPICE Simulator Graphical post processor...

Unfortunately, the lab used in the creation of the circuits in this book closely resembles the lab of other engineering companies around the world. We use 5% tolerance resistors and 10% tolerance capacitors that are either soldered to a vector board or plugged into a solderless breadboard. This introduces various parasitics and inaccuracies in the results. In order to be more precise in showing the accuracy of SPICE simulation software, we frequently run the simulations with the stated values of the resistors or capacitors used in our lab breadboards. The measured values for each resistor and capacitor used in our breadboard configuration which may be different, are shown in Fig. 3.3. 

Other important characteristics of the converter are the reflected ripple attenuation and the turn-on characteristics. It is expected that the turn-on characteristics will be difficult to simulate because of the nonlinear characteristics of a saturating core. A nonsaturating core is simply described by Faraday s law, and it can be easily modeled by any of the SPICE simulators. The model used for the EMI filter is shown in Fig. 3.66, and the results of each of the simulators output and the measured impedance plots are shown in Figs. 3.67 to 3.70. 

SPICE tip The optimizer function of the SPICE simulators is tailor made for this problem. The optimization feature can be performed in Micro-Cap by using the STEPPING feature in the AC menu, and in PSpice by using the PARAMETRIC sweep in the setup dialog box. In IsSpice, the OPTIMIZER sweep menu is selected by selecting the SIMULATION CONTROL item in the ACTIONS menu of ICAP. 

Table 4.4. shows that the final converter performance numbers using PQ2620 transformers are in excellent agreement with SPICE simulation data produced by PSpice. 

Examining the results of the SPICE simulations, it is noted all of the simulations show a slight current charging at the beginning of the... 

These results show that all three of the SPICE simulators were not equipped to handle simulations of this particular zener diode in its soft region. However, zener diodes are not well defined or tested in this region of operation, so it may just be that the circuit tested had a worse than average zener diode in it. To further explore this problem, the experiment was modified to put more current than the specified test current in the zener diode. The circuit with these modifications made is shown in Fig. 6.64. The measurements across the zener diode are shown in Table 6.6, and the the resistance-to-voltage response is contained in Fig. 6.65. 

The resulting output of the breadboard is shown in Fig. 8.47. The outputs of the SPICE simulations are shown in Figs. 8.48a and 8.48b. The output of the circuit is a clean, low-distortion 500 Hz sine wave. 

The only real error source for the output voltage are the forward drop characteristics of this diode. Each of the three SPICE simulators has a model for the 1N4002 diode, with all of the simulators within about 100 mV of each other. The question is, which model is correct The answer is they are probably all correct. The forward drop tolerance of a diode varies from lot to lot, from manufacturer to manufacturer, and from device to device. Table 10.1 shows the results of each of the three simulators along with the breadboard results. 

The investigations to obtain high lateral resolutions were accompanied by different simulations and models for LAPS devices. Beside generic electrical representations and SPICE (simulation program with integrated circuit emphasis)-based simulations [45,46],... 

SPICE Simulation program with integrated circuit emphasis... 

Fig. 15.2. AIM-SPICE simulation of a mediocre pentacene thin film transistor. A. Drain current as a function of gate-source voltage. B. Drain current as a function of drain voltage.

Nagel L.W., SPICE (simulation Program with Integrated Circuit Emphasis), Tech. Rep. ERL-m382-1977, Electronics Research laboratory, University of California, Berkeley (1977)... 

We built SPICE models for the critical paths in both implementations. The parametric RC parameters for in-chip layout structure are extracted using a commercial tool1 41. Obviously, full-chip SPICE simulation would be infeasible. Accordingly, we built a partial layout specifically for RC parameter extraction. The partial layout includes the original logic circuits, driver buffer, bus wire belong to a specific critical path as well as 3 neighboring wires on both side and typical layout structures in adjacent metal layers. 

The calculations in this chapter, and many more electronic calculations, can be done by computer with the program "SPICE" (Simulation Program with IC Emphasis), from Microsim Corp., Irvine, CA (www.microsim.com). Also, a low cost demonstration version is available from Intusoft, in San... 

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