Created by Created May 23, 2012 Last modified June 11, 2013 Tags

Summary

A very simple model of a typical optocoupler.

I thought I'd seen one somewhere in CL but I couldn't find it so here's one I made earlier ...

Description

A very simple model of a typical optocoupler.

I thought I'd seen one somewhere in CL but I couldn't find it so here's one I made earlier ...

Ictr1 is the (LED current)*(the datasheet CTR value)/(Q1_hFE)

In this example CTR=60%

More complex models take account of the non-linearity of the LED optical power o/p vs current characteristics and may have detailed modelling of rise and fall times and propagation delay.

Note that, although D1 provides a load that represents an LED, in terms of voltage drop, resistance and junction capacitance etc., the LED model has no optical parameters. The only coupling to the receiver is via the behavioural current source Ictr1 monitoring the current through D1.

Simulate > DC Sweep > Run DC Sweep

https://www.circuitlab.com/circuit/95w75k/optocoupler-02/

https://www.circuitlab.com/circuit/v28w66/optocoupler-03/