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Old 12th April 2012, 06:10 PM   #51
SY is offline SY  United States
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He wants to maximize the output impedance of a tube-based CCS (where high output Z is desired), not a voltage amplifier stage. It was a sudden conversational lurch that left a few people behind.
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Old 12th April 2012, 06:27 PM   #52
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Ah, yes. Lurch indeed. But that's not what confused me. It was the "output" part. Most people think of a CCS as a 2-terminal device, so it doesn't have an "input" or "output". Even when its physical realization happens to be multi-terminal.
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Old 12th April 2012, 08:53 PM   #53
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The pertinent point is that every circuit needs considering on its own terms and that this is easy to miss when you are using other peoples ideas - I know I have used things inappropriately when I failed to understand the underlying concept.

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Old 13th April 2012, 10:13 AM   #54
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A CCS has an output, it just doesn't have an input. It outputs current, and you want the output impedance to be as high and linear as possible. People sometimes seem to forget about the 'linear' bit, but provided the impedance is high enough you can get away with this.
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Old 13th April 2012, 11:38 AM   #55
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with CCS the input is the source of voltage or B+, the output is current flow with very high impedance, think Norton.....
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Old 13th April 2012, 12:25 PM   #56
dgta is offline dgta  United States
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You guys are funny. But sure, make up your own definitions, why not.

Later on today I'm going to order some resistors with very linear output
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Old 13th April 2012, 12:28 PM   #57
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Quote:
Originally Posted by dgta View Post
You guys are funny. But sure, make up your own definitions, why not.

Later on today I'm going to order some resistors with very linear output
Do you imagine that a CCS doesn't have a response curve ?

Now that really is funny

To my certain knowledge just about every component imaginable has a response curve which needs to be considered.

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Old 13th April 2012, 01:08 PM   #58
TheGimp is offline TheGimp  United States
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Since current sources are composed of non-linear devices, how could their output be linear (over a large enough current range)?

Sim some current sources and look at the differences in distortion. It is quite revealing. You might also try varying the source voltage driving them to see how it effects distortion.

Or for those of you who don't believe in sims because they are only approximations, build several current sources and measure the distortion.
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Old 13th April 2012, 01:22 PM   #59
AJT is offline AJT  Philippines
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as i understood it, this thread was about replacing the traditional resistor capacitor combo with LED's on common cathode circuits......and in this aspect LED's rocks......

why look a tube CCS's when sand is freely available?

Last edited by AJT; 13th April 2012 at 01:26 PM.
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Old 13th April 2012, 01:31 PM   #60
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Because the use of LED's in other situations is inappropriate and it would be easy to go away from this thread thinking that they are the solution to everything. If nothing else this CCS aside will have given beginners pause for thought when they "imagine" that LED's can work everywhere.

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