I'm looking for the min and max IF current for the input of the H11AA1 AC INPUT/PHOTOTRANSISTOR. I have a bit of a problem reading the datasheet. https://media.digikey.com/pdf/Data Sheets/Fairchild PDFs/H11AA_1,2,3,4.pdf
I have a circuit with 26vAC input with 3K resistor on the input of the LED, I believe about 10mA. What would be the Min mA? What would be the Min and Max voltage input with 3K on the input? If I read the datasheet 60mA would be Max current. Some datasheets have the info. much clearer.
Thanks for your help!

 

hi Tom
Page 3 of 7 covers the emitter current specification.
What low emitter current do you want to use.?
E

 

The emitter show 100ma, anything just below this should be OK, minimum ~60ma I would say.
Max.

 

there is "LED power dissipation" (at the very beginning) 200mW - 2.6mW · (T - 25°C) /// up @ 100°C max 200mW - 2.6mW · 75°C = 5mW
use Fig. 1 Input Voltage vs. Input Current to estimate your P.LED and/or R.LED @ I.F.LED (the actual P & R may be greater or lower by ?? up to ±20%)
the thermal resistance of the chip can be somewhat estimated by the given 1A @ 300Hz duty 1us/3333.(3)µs (0.03%) the bad thing is we donno is it per LED or 150Hz per single LED (the d/s is a bit of a nightmare)

Continuous I.F.MAX 100mA has average 1.5V drop 15Ω dynamic resistance → 150mW (? @ T.j 25°C ?) . . .
you need to estimate or derive experimentally the R.Θ.ja
. . . /!\ speculating :: 200mW max ,150mW → T.j = 50mW/2.6mW + 25°C = 44.23°C at junction ← will give R.Θ.ja =50mW/2.6mW/150mW = 128.2°C/W ← https://www.rohm.com/electronics-basics/transistors/calculating-transistor-temperature . . . for 1A/µs → 30mA "RMS" the LED U.FW is not avail ← it may go ramping up at high end -e.g.- the dynamic resistance might start climbing along with dissipated power causing the "excess heating of the junction" compared to the continuous lower current /!\

 

I just don't want to run on the fringes of the low limits. Inputs may very and would like to know the limits with 3k on the emitter circuit. Min and Max voltage with 3k would be great to know. Thanks!

 

hi Tom
Page 3 of 7 covers the emitter current specification.
What low emitter current do you want to use.?
E

THE TS is asking about the LED current, not the output transistor current.

 

hi M,
A 26V AC supply with a series 3K will give a 8mA to10mA peak current
E

Update:
At that peak current you should get a CTR of 0.8

 

10ma a little low, even the 50ma rated versions I run at around 40ma.
Max.

 

I was worried about being to low with 10mA +_ So maybe 30-40 mA would be more optimum?

 

I was worried about being to low with 10mA +_ So maybe 30-40 mA would be more optimum?

At least, I would think.
Max.

 

hi M,
What is the opto output driving into.?
E

 

The H11AA1 is driving a CD4093 Schmitt-trigger circuit with a 10k pullup on the input and a .1uf cap to GND.

 

At least, I would think.
Max.

but if the opto is driving a cmos gate input it doesn’t need to provide much output current. 10ma is probably ok as long as it turns on the output transistor for the input supply range.

eT

 

To look at the input curve for the LED's 10ma is getting near the knee of the operating curve before it flattens out!
I prefer not to operate that close to the edge.
Max.

 

in contrast the Fig. 2 shows the CTR greatest at I.F.inp from 2...10mA
for H11AA1 the CTR ≥ 20% (0.2) means output current 400µA...2mA ((conflicts with ▼))

doesnot likely apply here → the real transistors like to work from ≥ 4mA base current

(the best outp ON/OFF timing is got with 100kΩ base shunt) ← we need hFE here but we don't have it
the 100kΩ base shunt usually works good with 10kΩ base resistor the LED generates about the same voltage from light @ what it's I-V curve flattens out ? 1.5V =
= (1.5-0.65)/10kΩ ≈ 85µA of Photo-Current √(0.4·2)≈1mA Ic → wild guess for h.FE (ß) ≈ 12 (the one typical for RF/Switching.HV transistors ?)
a different circuit has RB:RB.shunt best ratio 2:3 -e.g- 67k:100k → ß ≈ 80 (but it's with strong drive current , where the output triggers another input , that is biased near threshold -- in a switching circuit = less likely here with the the linear dependency ) but you can easily measure both the ß and the photo-current ... with-counting the dark-current provided on d/s (up to 10µA)

other than above -- there was a reason to use near I.F.max switching currents (likely the storage time related) ((conflicts with ▲))

 

THE TS is asking about the LED current, not the output transistor current

You're a pain in the behind why don't you contribute rather than criticized all the time?

 

You're a pain in the behind why don't you contribute rather than criticized all the time?

That certainly was not intended as a critical remark, but rather to keep the responses aimed at the questions asked.