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Old 19th September 2019, 07:51 PM   #1561
Zen Mod is offline Zen Mod  Serbia
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just build the damn thing .....


you can't make it both better and simpler .......
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Old 19th September 2019, 08:02 PM   #1562
JeffYoung is offline JeffYoung  Ireland
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What, and skip the over-analysis / audio-nervosa part? That would be cheating.
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Old 20th September 2019, 03:25 PM   #1563
EUVL is offline EUVL  Europe
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Default Opto-Coupler Variations

I only bought 4 pieces of CNY17-3, so they are likely to come from the same production batch.

I have measured them all, the aim being to generate a 2mA current at the photo transistor with ~2.1V Vce.
The LED Vf varies from 1.087 to 1.095V; and the CTR from 0.93 to 1.01.

As they are, when put into the circuit as posted, the output bias will vary between 1.267A and 1.299A.
(Simulation says 1.16A. So a difference of 12%.)

One can say that 32mA difference in bias is negligible, which is true.
But the measurement does not say anything about batch to batch variations.
So other examples bought from different suppliers might differ, by up to 20% according to datasheet.
But at least variations within a batch seem acceptable.


Patrick
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Old 20th September 2019, 05:13 PM   #1564
Itsmee is offline Itsmee  England
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I still haven't learnt to sim I wonder how much variation there would be with a ZTX450/BC547
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Old 20th September 2019, 05:25 PM   #1565
EUVL is offline EUVL  Europe
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Time to learn.

I have already done all the work for you.
You just need tzo download and run.

And google.


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Old 20th September 2019, 06:23 PM   #1566
Dennis Hui is offline Dennis Hui  Canada
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Hi Patrick,

Thank you kindly for posting your spice files. Lots of experimentation
ahead.

Cheers,
Dennis
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Old Yesterday, 04:37 PM   #1567
JeffYoung is offline JeffYoung  Ireland
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I ran my batch of four 4N35 through a test rig similar to its operation conditions: variable bench-top supply through 100R to LED, 24V bench-top supply through 15K to BJT.

I measured the voltage over the 15K at LED voltages of 1.05, 1.10, 1.15 and 1.20.

Sample 1: 1.3, 4.2, 9.6, 17.4
Sample 2: 1.3, 4.2, 9.8, 17.3
Sample 3: 1.4, 4.2, 9.7, 17.0
Sample 4: 1.2, 4.0, 9.1, 16.0

So 3 are virtually indistinguishable on my test rig, but the 4th is about 10% off. At a target of 1.3A bias my sim shows that I'll get 1.29A vs 1.41A (nearly 4 times Patrick's result).

This could be the afore-mentioned batch-to-batch variation (ie: different wafers between the first 3 and the 4th). In any case mine are now matched and there seems little to gain by mixing them up again.

Cheers,
Jeff.
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Old Yesterday, 05:25 PM   #1568
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Heat it up to 50C (as inside the amp case) and see what happens.


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