How to simulate the CNY70 IR reflectometer with TINA or LTSpice
What I meant was to use a transistor with a current source in the base, which is meant to represent the luminosity. Something like this:

This is not meant to represent the CNY70, rather to show how it could be done. You will need much more than a wet finger in the wind (my approach) to model the diode and the transistor (I used some round numbers; the β is too low). As it is now it roughly has 1m &lt;&gt; 50u, 10m &lt;&gt; 500u, 100m &lt;&gt; 5m (compare with fig. 5 in the datasheet). At any rate, the value for F1 will set the amount of luminosity in the base, and because the law is logarithmic by nature, you should get something similar to fig. 9 in the datasheet.