# what is normalized CTR

Discussion in 'Homework Help' started by Kardo22, Aug 6, 2014.

1. ### Kardo22 Thread Starter New Member

Mar 12, 2014
26
0
Hi
Can someone give me a definition for normalized current transfer ratio?
Google only gives me datasheets as results, nothing useful

2. ### Papabravo Expert

Feb 24, 2006
10,179
1,800
Current Transfer Ratio tells you how much current you get out of an optcoupler for a given amount of current used to light up the diode. To normalize this you would need to establish a reference level and express CTR relative to this reference level. I don't really see much use in doing this since CTR is already dimensionless and is scaleable. Can you give us some context that prompted your question.

3. ### MrAl Well-Known Member

Jun 17, 2014
2,442
492
Hi,

Things like CTR are often normalized so that we can quickly see how the quantity changes with some other change of variable. This makes it much quicker to see how the response changes when something else that normally could change changes. When this is done it is most often done with the quantity being normalized to some reference level of the variable along the abscissa. That gives a quick percentage change view which helps us quickly access the device in question as to how it functions in our application.

For example, the CTR might be 50 at 20 degrees C, but might change to 45 at a higher temperature and 55 at a lower temperature. So that gives us three values for this small example:
45, 50, 55

Normalized to 20 degrees C, we would see:
0.9, 1.0, 1.1

and from this we can quickly access how the 'gain' is going to affect our output without having to calculate the output with every single CTR possibility.