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Can an optocoupler be wired to give both inverting and non-inverting logic output without additional active components?

I'd like to avoid using an inverter if possible, but also curious as to whether this is trivially possible.

Suppose I am talking about a normal PC817 with phototransistor output. Also I want both outputs to be isolated.

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  • \$\begingroup\$ Why do you want to avoid extra components? \$\endgroup\$
    – jippie
    Feb 28, 2016 at 18:42
  • \$\begingroup\$ You could add both (or either) a collector and emitter resistor, resulting in a symmetric output, but I'm unsure how that changes rsponse characteristics. \$\endgroup\$
    – jippie
    Feb 28, 2016 at 18:48
  • \$\begingroup\$ I am using 24V logic, and my supplier doesn't seem to have such inverters, also one less entry in the BOM. \$\endgroup\$
    – akaltar
    Feb 28, 2016 at 18:48
  • \$\begingroup\$ A single transistor and one or two resistors make an inverter that easily copes for 24V. \$\endgroup\$
    – jippie
    Feb 28, 2016 at 18:50
  • \$\begingroup\$ @jippie probably thats what I'll resort to, but I am an amateur, so I rather asked to be sure. \$\endgroup\$
    – akaltar
    Feb 28, 2016 at 19:06

3 Answers 3

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schematic

simulate this circuit – Schematic created using CircuitLab

Figure 1. Inverted signals from single opto-isolator. Note that outputs do not cross and are unlikely to switch any standard logic properly.

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If you want full logic swing 0-24V signals then it will be necessary to add one more transistor and a couple of resistors like this:

enter image description here

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  • \$\begingroup\$ This is the approach I will take, but I have accepted transistor's answer, because I asked about not using actives. Still great answer. \$\endgroup\$
    – akaltar
    Feb 28, 2016 at 19:19
  • \$\begingroup\$ I believe that in relation to LED current your outputs are marked inversely. \$\endgroup\$
    – akaltar
    Feb 28, 2016 at 19:26
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Another option with near identical response times between the channels (at the cost of extra components) and both channels near full swing.

schematic

simulate this circuit – Schematic created using CircuitLab

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