The depth of nested subcircuits (like the one above) is not limited. ... Another excellent feature of the DC sweep in LTspice, is the ability to do a nested sweep. If the variable subinvoke is set, then it is used as the prefix that specifies instances of subcircuits, instead of 'x'. For example, a Spice netlist is a list of state-ments and control lines. Subcircuit Calls General form: XYYYYYYY N1 SUBNAM Examples: X1 2 4 17 3 1 MULTI Subcircuits are used in SPICE by specifying pseudo-elements beginning with the letter X, followed by the circuit nodes to be used in expanding the subcircuit. The translator handles this by writing each subcircuit definition separately in order of occurrence. A statement is a list of But some SPICE programs didn't allow nesting subcircuit definitions at all. .ends inner2 .ends inner .ends outer Not all SPICE programs handle these the same. There is no limit on the size or complexity of subcircuits. Definitions may be nested and/or invoke other subcircuits. SPICE allows you to define a collection of elements as a subcircuit (e.g. an operational amplifier) and to insert this description into the overall circuit (as you would do for any other element). CONTROL CARDS.TEMP Card Spice 3: Subcircuits may be nested in the SPICE file; however, ADS does not allow this. Generally there are two different ways. You have to use the whole "code" part of the OPA188.lib file (copy it into "your" library). features, commands, and procedures. Defining a subcircuit Adding your own SPICE Models or Subcircuits How to add a model to LTspice (SwitcherCad) This assumes you want to add a new model for a new device similar to one in the existing library. All the hierarchical subcircuits appear correctly as text subcircuits, including any parameter passing statements. 3. MacSpice uses the definition as a template wherever the subcircuit is invoked. My guess is that it wasn't included in Berkeley SPICE, but was added afterwards. Subcircuit Name Expansion In order to refer to internal nodes, devices and models inside subcircuits you must know how the names are expanded before the netlist is parsed. If there are several nested subcircuits, node and device names look like subckt1:subckt2:...:name. Line by line comparison with the original netlist will be harder in … 220-spice-notes.tex Page 5 Passive Elements The that begins an element instance denotes the circuit element.The passive elements are Ror rfor resistors, Lor lfor inductors, and Cor cfor capacitors. Code generation: A valid Matlab code is generated from the transformed abstract syntax tree and the associated symbol ta- ... the Spice concrete syntax, and represented as a set of ’type’in Gentle. Subcircuits But what if you want a realistic op-amp model? This is followed by a unique instance name and then (in order) the nodes associated with + and - voltage and the value of the associated parameter (R, L, or C). There are a few other (nested) subcircuits defined in this library file, among them .SUBCKT RNOISE_FREE_0, .SUBCKT RNOISE_FREE_2, etc., that are used (called) within the main .SUBCKT OPA188 during simulation. SEE ALSO nutmeg(1), sconvert(1), spice(1), mfb(3), writedata(3) SPICE3 User's Guide AUTHORS Subcircuit Expansion In order to refer to internal nodes, devices and models inside subcircuits you must know how the names are expanded before the netlist is parsed. This manual is not a book about learning SPICE usage, however the novice user may find some hints how to start using ngspice. The netlist for the instrumentation amplifier circuit above: CW180402-06.lib; comprises one subcircuit defining the 741 op-amp: The name is needed only when nested subcircuit definitions are being made. That’s where subcircuits become useful. Chapter 21.1 gives a short introduction how to set up and simulate a small circuit. vice names in the nested subcircuits. The depth of nested subcircuits (like the one above) is not limited. I think the original Berkeley SPICE allowed the former, so presumably all other SPICE programs do too.