https://www.mouser.se/datasheet/2/308/MOCD223M-D-1811661.pdf

CTR of this optocoupler is specificed to minimum 500% at If=1mA and Vce=5V.
How do I read out Vce for If=8mA and Ic=140mA? I think figure 4 and figure 6 can be used.

(I get Vce=1,1V when I play with it using the If=8mA and Ic=140mA)

 

hi bh,
Have you seen this graph from the d/s.?
Post your circuit.
E

 

Yes, I added "I think figure 4 and figure 6 can be used" to my question right after I posted it. I did not think anyone would reply so fast.
Figure 4 gives the value "5" from the y-axis with If=8mA. Does that mean the CTR(min) is 500%*5 = 2500%.
If so, that is however with Vce = 5V. I need to figure out Vce when Ic=140mA.

 

On the datasheet, the graph for Output Current vs Input Current is not a straight line. 1mA input is guaranteed in writing to produce at least 5mA output but 8mA input will "typically(not guaranteed)" produce only 40mA output. you are lucky that yours produces 140mA.

The saturated Vce is the output from the darlington which is max 1.0V when input is 1mA and output is only 0.5mA. It might be as high as 2.5V with your 140mA output and produce some magic smoke.

 

hi,
It would help if you could post a circuit showing what you are trying to do.
Your description is misleading.
E

 

I just run 8mA through the LED.
24V and a resistor to the collector. Emitter to 0V.

 

On the datasheet, the graph for Output Current vs Input Current is not a straight line. 1mA input is guaranteed in writing to produce at least 5mA output but 8mA input will "typically(not guaranteed)" produce only 40mA output. you are lucky that yours produces 140mA.

Isn't that where figure 4 comes in and multiplies CTR by a value of 5 with If=8mA?

 

Verbal descriptions are useless. Post your circuit diagram!

 

hi,
All thats needed is say 1mA to 2mA Opto emitter current.
Assume a White LED say 3.0Vfwd, from 24V thats Rcoll = 21V/8mA thats a approx 2k7
E

 

As my Ic=140mA, the resistor from 24V to collector is 24V/0,14A = 163ohms.

 

I just run 8mA through the LED.
24V and a resistor to the collector. Emitter to 0V.

How can your Ic be 140mA with a 8mA LED.
If you post a circuit I am sure someone will help you.

 

If is 8mA.
Ic is 140mA

There is no white LED in my application.

 

The schematic is just like figure 8 in the datasheet, except Vcc = 24V instead of 10V. RL = 160ohms.
I run If at exacly 8mA.

 

OK,
I see the circuit in the d/s.
You will get ~140mA Ic for a 8mA Emitter drive.
Exactly what are you trying to do.?
E

 

For me is to understand how to apply the normalized values.

Can you plesse explain how you got the ~140mA?

And maybe if you please can help
me answering the original question "How do I read out Vce for If=8mA and Ic=140mA? "

The CTR values in the d/s is for Vce=5V.

My experiments gave Vce=1,1V.

 

The Vce for a single saturated transistor is about 0.1V to 0.2V but it could be as high as 1V.
The Vce for a saturated darlington pair of transistors is about 0.8V but could be as high as 2.5V.
Yours is saturated with a Vce of 1.1V.

 

Can you plesse explain how you got the ~140mA?

(Vcc-Vsat)/Rc ..... (24V -1.1V)/160R = 143mA.

 

I know that is it saturated in my application, but how do the datasheet confirm that it is in saturation using CTR 500%, If=8mA, Ic=140mA using figure 4 and 6? If I would reduce If for examples, the Vce would increase. It should be possible in some way to get the Vce when the other parameters are known.

 

The curves in the datasheet are for a "typical" one that you do not have. They cannot make them all the same. Some are better and some are worse than "typical" but yours is better.

 

As you have seen, opto couplers are not easy to tightly specify, They wander with PVT more than any other device I know of.

Notice that the data sheet graphs show the normalised numbers on the Y axis, and that the data sheet graphs are for "typical" characteristics.

I read through the above and am now confused as to what the OP requires.