What do the triangle and rectangle represent in an optocoupler diagram?

[nothing909]

Homework Statement

In that pin configuration, what does the triangle and rectangle in the middle represent?

 

[gneill]

A triangle typically represents an amplifier of some sort. A rectangle could represent anything from a resistor network to additional transistor switching circuits.

The schematic representation of a component is generally meant to convey the most basic operational functional blocks inside the chip that the user needs to be aware of. Here the important things for the user to know is that there's an LED, a photodiode with amplification of some sort, and some logic driving a "totem pole" output (the two output transistors).

 

[CWatters]

The rectangle converts the output of the amplifier into two different signals one for each of the output transistors. Typically it performs a level shift type function to correct (not quite the right word) for the effects of the 0.7V Vbe of the transistors.