For a normal optocoupler with a LED and a phototransistor, we can put the load resistor (RL) at the emitter or the collector of the phototransistor, just like this

enter image description here

But for a high-speed optocoupler with some other digital logic inside, like HCPL-060L, it seems the pull-down version should not work, right?


As you can see in the datasheet, this optocoupler uses a (Schottky-clamped) transistor between the output and ground pins:

HCPL-260L schematic

This output is designed to be used with a pull-up resistor.

The chip requires that its supply voltage (VCC relative to GND) stays constant, and the output transistor is switched on by raising its base above GND, so it is unlikely that you could manage to do anything interesting with the GND pin.


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