Photo-relay (SSR) Am I being dim?

[itdontgo]

http://www.digikey.co.uk/product-detail/en/TLP3120%28F%29/TLP3120F-ND/871294

TLP Photo-relay

I have tried two of these devices and I'm getting an output resistance of 20ohms; 10ohms per MOSFET.  Some way off the specified 0.15ohm output.  It's being driven by 26mA through the LED.  Can it really just be a dud batch or have I missed the point here?

With a 12V PSU and a 27ohm load it gives a resistance of 22ohms and with the multimeter I get 20

[Zero999]

According to the catalogue, it seems like you're not supposed to use the output transistors separately.

Connect pins 4 and 6 in series with the load, leaving pin 5 unused.
http://dkc3.digikey.com/PDF/CN081/2097.pdf

[wraper]

According to the catalogue, it seems like you're not supposed to use the output transistors separately.

Connect pins 4 and 6 in series with the load, leaving pin 5 unused.
http://dkc3.digikey.com/PDF/CN081/2097.pdf

+1

[itdontgo]

Yes that's what gives us 20ohms.  If you have DC you can use one transistor to reduce the output resistance but if it's AC you need to use both of them.  But as I say I'm measuring it and it's 10ohms per transistor.  Hmmm.  I have new stock arriving shortly maybe it's just a problem with these.  I thought I am making a stupid obvious mistake that someone would point out!

The reason I have my doubt btw... they came from China from an unknown dealer

[T3sl4co1l]

So wait, why give a Digikey link when it's not even authentic Digikey?

If you're paying bottom dollar for it, don't expect functionality, expect crap.

Tim