I have a requirement to model an optoisolator in LTSpice. The optoisolator has an input LED that shines light on a photovoltaic cell on the output. Current in the LED will cause light to fall on the photovoltaic cell and cause a voltage to be generated on the output. I have measured the input-current-to-output-voltage characteristics of the device - Vout=F(Iin). The transfer function F is somewhat nonlinear. I have created a table of measurements listing the output voltage for a set of specific input currents. Now I am trying to build an LTSpice model that functions similarly to the actual device.?
A simple first-order approximation of the device would be a current-controlled voltage source with the transfer function defined as a table. i have tried all kinds of ways to define the table in a LTSpice current-controlled-voltage-source, but no luck. Can anyone show me how to do this? What does the spice directive look like, and where (and how) do you put it in LTSpice?
A second-order model will need to take into account that output impedance will also affect the output voltage (at low impedances the output becomes more like ?a current source), but that is for another day.
