AWR eBooks

RF Electronics Chapter 2: Computer Simulation Page 18 2022, C. J. Kikkert, James Cook University, ISBN 978-0-6486803-9-0. AWR DE includes advanced Hybrid Pi (HYBPI) and T (BIP) models, which include lead inductances as part of the Linear Devices circuit elements. As an example, the BIP linear model of a transistor, shown in figure 2.18. The lead inductances are normally ignored for lower frequency models. The user must determine the element parameters for the device used from equations, like used in figure 2.16, the manufacturer's data sheets or measurements. S parameter measurements of circuits and devices, can be made at RF and microwave frequencies and allow S parameter models to be used as part of simulations. For example placing the uPC8181TB MMIC amplifier from Renesas in a circuit, by selecting Element Libraries AWR Web site Parts by Type Data Renesas IC 1_Wide_Band_Amp uPC8181TB Vcc=Vout=3V Icc=23mA. Inserts a 2-port subcircuit in the circuit schematic that contains an S parameter file for the model. As shown in table 6.1 in example 6.3 in Chapter 6, for some MMIC's only S parameter performance data are available. In Chapter 9, figure 9.6 shows that for high power active devices, large signal S parameters are often specified. S parameters are a linear measurement based representation of a device, and just like the T and Hybrid Pi transistor model, those models assume the correct biasing has been satisfied and these linear models cannot handle clipping caused by the output signal being large. Nonlinear Models The second type are non-linear analytical models. MWO includes Angelov, Gummel- Poon, Parker-Skellern, SPICE, Statz and Volterra based transistor models. Simulation Program with Integrated Circuit Emphasis (SPICE) based models can accurately model both the linear and non-linear parameters of a device. SPICE models are available for simple devices like resistors, capacitors, inductors, transistors and diodes or complex devices like MMIC's and operational amplifiers. The original versions of SPICE [12] are covered by a permissive BSD licence. However, since the release of SPICE1 in 1973, many different companies developed their different versions of SPICE models. Some of those are HSPICE and PSPICE (owned by Cadence). Some semiconductor manufacturers developed their own SPICE simulation software for their own devices. Analog Devices developed LTSpice [13], Texas Instruments developed TinaTI [14] are examples of these. This lack of compatibility means that many SPICE device models will not easily import into programmes like AWR DE. To overcome this, in 1996 the Compact Model Coalition was formed to promote standardization of compact model formulation and their interfaces, with the aim of allowing the complying SPICE models to be used in different simulation software. AWR is a member of the CMC. In 2013 the Silicon Integration Initiative (Si2) [15] took over the operation of the CMC. NXP has developed SiMKit [16] is a simulator-independent compact transistor model library. Connections for different simulators are handled through adapters that provide the right interfacing to those simulators. The latest releases of AWR DE, includes circuit element libraries with CMC Models, SimKit 4.7 Models, APLAC models, IC Foundary Process Design Kit (PDK) models as well as both SPICE and S parameter models of many devices. These libraries can be seen by selecting Circuit Elements Libraries AWR web site. These non-linear models permit an accurate analysis of a transistor circuit. The Gummel- Poon Transistor model [17] included in AWR DE has the circuit diagram shown in figure 2.19. The model includes some device non-linearity and is significantly more complex than the BIP model shown in figure 2.18. Details of the Gummel-Poon model for a BC546 transistor can be seen by selecting Circuit Elements Libraries AWR web site Parts by Type Nonlinear Zetex GBJT NPN BC546bp, and placing the RF Electronics: Design and Simulation 18 www.cadence.com/go/awr

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