Voltage Source Opto XX?

Thread Starter


Joined Jul 11, 2019
Hey There,

so looking into Optocouplers, I just realized that the output is a transistor controlled by the light from the input - I (for some reason) thought it was a voltage source like a solar panel.
Anyways, this would have funny, maybe stupid applications, like generating very high isolated voltages by connecting the output in series while the input can be paralleled.
Or, as in my case, I was wondering whether one could connect the negative side of the output to the source of a N-Mosfet and the positive side to the gate, allowing a high side load switch.

Are there such (optocoupler-like, voltage source) devices and if yes, what are they called?

Thank you


Joined Jan 29, 2010
Hi A,
The opto output does not generate any usable voltage, the emitter diode just sets the output transistor into conduction



Joined Apr 4, 2016
Although theoretically you could have a package containing a LED and a photo-diode and generate some isolated voltage, the power generated would be very small. Better to use a miniature DC-DC converter. These are quite cheap and widely available.
Isolated high-side switches with a LED and a photo diode coupled to a MOSFET switch are available. Look-up "MOSFET SSR" (MOSFET solid state relay).

Thread Starter


Joined Jul 11, 2019
This is a link to one type of PHOTOVOLTAIC opto coupler. It gives an output voltage but at a very low current. It could drive the gate of a mosfet.

that's exactly what I was looking for! Though compared to Optocouplers, they seem to be a niche product and priced accordingly ;) As marley pointed out, DCDC is much cheaper, for my application a charge pump would do too since a mosfet doesnt consume current to stay on.
At least I am not missing out on something. Thank you all very very much :D