Work with specifications

Working with specifications is a powerful feature of SLiCAP. Specifications can be read from and stored to CSV files. Editing of the CSV file with a spreadsheet program or a text editor is possible but not preferred.

The preferred way of working is to create SLiCAP specItem objects. Detailed information about specItems can be found in the specItem().

The example below shows how to create a list with specifications. In this example we will define four specifications for a transimpedance amplifier:

1. The typical value of the signal source cpacitance in F; this is considered an ‘interface’ specification

2. The target value of its current-to-voltage transfer (transimpedance gain); this is considered a ‘functional’ specification

3. The target value of its -3dB bandwidth; this is considered a ‘performance’ specification

4. The target value of its (unweighted) RMS output noise; this is considered a ‘performance’ specification

The designer is free to define any type of specification. In reports, SLiCAP places specifications of the same type in one table.

# Import SLiCAP modules in a separate namespace
import SLiCAP as sl
# Create SLiCAP project
sl.initProject("Specifications")
# It is convenient to define the values at the top of the file
# This makes it easy to modify them
Cs = 10e-12 # Typical value of the source capacitance
Zt = 1e6    # Target value transimpedance gain in Ohm
Bf = 5e4    # Target value -3dB bandwidth in Hz
Vn = 5e-4   # Maximum unweighted RMS output noise voltage
# Now assign these values to specification items and put these items in a list
# Create the list
specs = []
# Create specification items and append them to the list
specs.append(sl.specItem("C_s",
                         description = "Typical value of the source capacitance",
                         value       = Cs,
                         units       = "F",
                         specType    = "Interface"))
specs.append(sl.specItem("Z_t",
                         description = "Target value transimpedance gain in Ohm",
                         value       = Zt,
                         units       = "Ohmega",
                         specType    = "Functional"))
specs.append(sl.specItem("B_f",
                         description = "Target value -3dB bandwidth in Hz",
                         value       = Bf,
                         units       = "Hz",
                         specType    = "Performance"))
specs.append(sl.specItem("C_s",
                         description = "Maximum unweighted RMS output noise voltage",
                         value       = Vn,
                         units       = "V",
                         specType    = "Performance"))

The specifications will be stored in a CSV file with specs2csv()). The specifications are stored in the ‘sl.ini.csv_path’ folder. By default this id the ‘csv’ folder in the project directory.

The can be imported from this file with csv2specs()).

The example below shows how to store them in a csv file and import them from this file.

sl.specs2csv(specs, "specs.csv")   # Store the specifications in the file "specs.csv"
specs = sl.csv2specs("specs.csv")  # Import the specifications from the file "specs.csv"

Specifications can be assigned to circuit parameters using specs2circuit()). Circuit parameters that have the same name as a specItem() will then obtain the value of that specItem().

Specifications can be listed on the active HTML page using specs2html()).