spicemanual - Concise SPICE Ihsan Djomehri Spring 1999 1...

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Concise SPICE Ihsan Djomehri, Spring 1999 1 Introduction to Circuit Simulation Developed at Berkeley in the 70s, SPICE has evolved into the tool of choice for circuit level simulation. This handout seeks to provide a concise, fairly comprehensive introduction to HSPICE (version 98.2 running on MIT’s Athena network) and the graphing utility AvanWaves. I credit the authors of previous manuals for their information. In essence, SPICE reads in a list (called the “SPICE deck”) of circuit nodes and the elements between them, generates a series of nodal equations, and solves for the voltages. The deck also contains statements identifying which mode(s) the circuit should solve for: DC, AC, or transient analysis. Words of caution: many hacks have been introduced into SPICE over the years; always check the output to make sure it is intuitively reasonable! 2 Creating a SPICE Deck To start on Athena, make a new directory for your SPICE stuff, then type “add hspice” to add the HSPICE locker. Begin by sketching out your circuit on paper, labeling each node with a number, naming each circuit element and assigning properties to them. Note that node 0 is always ground and there can’t be any floating nodes. Use emacs to edit any text file like test.sp that will become our SPICE deck. An * in front of any line causes it to be interpreted as a comment. Later on, we will be using the circuit schematic in Figure 1 as a demonstration. The general format for entering in a circuit element is a one-letter identifier merged with a name, space, the node numbers that connect it, space, the properties of the element. Numerical property values are always in SI units (meters, seconds, volts, etc…) but can be modified by a suffix letter that acts as a multiplier: Suffix: t g x k m u n p f Multiplier: 1e12 1e9 1e6 1e3 1e-3 1e-6 1e-9 1e-12 1e-15 Thus, for various circuit elements we write (you modify italics, <>s are optional): Voltage: V name N+ N- <qualifier> value Current: I name N+ N- <qualifier> value Resistor: R name N+ N- value Capacitor: C name N+ N- value Inductor: L name N+ N- value Diode: D name N+ N- model_name BJT: Q name Nc Nb Ne model_name
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MOSFET: M name Nd Ng Ns Nb model_name L= value W= value <+ AD =value AS =value PD =value PS =value> where N+ , N- are node numbers from the positive to negative node; Nc , Nb , Ne are the collector, base, and emitter node numbers of a bipolar transistor; Nd , Ng , Ns , Nb are the drain, gate, source, and body node numbers of a MOSFET; model_name refers to a user specified element model; L, W are the length and width of a MOSFET; AD, AS are the areas of the drain and source to body interface, while PD, PS are their perimeters.
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spicemanual - Concise SPICE Ihsan Djomehri Spring 1999 1...

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