optocoupler 02 PUBLIC

A very simple model of a typical optocoupler.

Simulate > DC Sweep > Run DC Sweep

A very simple model of a typical optocoupler.

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 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.

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

In this example CTR=60%

D2 has no optical effect. It is present purely to model the reverse leakage (dark current) and junction capacitance effects of a photodiode.

Simulate > DC Sweep > Run DC Sweep

See also:

https://www.circuitlab.com/circuit/bdxks2/optocoupler-01/

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