Tolerance In Surface Mount Varactor Diodes

The ability to specify tolerance in the nominal capacitance has been added to selected models in the Modelithics Non-Linear Diode (NLD) Model Library in order to emulate the variation typically specified in manufacturer data sheets. The feature will be included in additional models in future library releases. This application note briefly reviews this new capability and provides suggestions on how it should be used.

A sample simulation schematic from Agilent's Advanced Design System is shown in Figure 1. Included in the schematic is the VAR_TSH_TG1A_005 model for the Toshiba P/N 1SV280 varactor diode. The model parameter used to specify the capacitance tolerance is Cap_tolerance – this parameter should have a nominal value of 1, with the tolerance specified as a percentage (in this case /- 12%). The Res_tolerance parameter can be used in a similar fashion to emulate variation in the series resistance of the device, another parameter that is often specified by diode manufacturers.