New CCS Idea

[chalky]

Has anyone tried the back to back led and transistor ccs ( sijosae collection no12 ) or the back to back dual transistor ccs ( sijosae no 16 )? I use the no12 circuit frequently and published a note on it in Electronics World a couple of years back after discovering it in an ancient textbook. In theory it shouldn't work, and it doesn't simulate, because there's nothing to get it started. One explanation I have heard is that the leds act as photovoltaic devices; but the circuit works in the dark, and I've never been able to measure any photovoltaic output from a led. I suspect that its just leakage that gets it going.
The no16 circuit as shown by sijosae I have never been able to get self starting. This may be transistor dependent because I think I've seen reports of the basic circuit starting up by itself. However if you put leds across the resistors it will self start 100% reliably and give the calculated constant current. The leds do not turn on in operation but again I suspect that leakage currents develop enough voltage across the led to kick start the operation? Any ideas?

 

[chalky]

Slight error in last post. The leds have to go across the collector and emitter of the outer two transistors to get sijosae 16 to self start reliably. This makes sijosae 16 look like sijosae 12 with a couple of extra transistors.

 

[ilimzn]

I'm sorry.

Above headphone amp circuit is not valid at all.
There was a big mistake.

Yes, B of the PNP transistor connected to -Vcc , but that is easy to spot and correct.

 

[sijosae]

chalky, you are correct.
No. 15 & 16 of my CCS collection did not self start.

 

[bscally]

chalky, you are correct.
No. 15 & 16 of my CCS collection did not self start.

OK..

So I do have a REALLY sore head.
I have run out of Coffee
I have been up all night working on a problem

But I am having difficulty finding the cross reference numbers.

post 15 or 16 don't seem to make sense.

I am REALY sorry to be a pain but this is an excellent topic and I want to follow it.


Brian

 

[chalky]

The numbers 15 and 16 correspond to constant current sources 15 and 16 in the diagram at sijosae's forum on http://www.headphoneamp.co.kr/

 

[mikeks]

chalky, you are correct.
No. 15 & 16 of my CCS collection did not self start.

The reason for this observation is elementary.....

Current sources must never be connected in series....just as bad as connecting nominal voltage sources in parallel...

 

[sijosae]

bscally,
My CCS collection means following link.

http://www.headphoneamp.co.kr/bbs/zboard.php?id=diy_sijosae&no=122

mikeks,
In No. 15 & 16, CCSs are not connected in series but in parallel.

 

[sijosae]

My progress with LM317-CCS

Simple Class AB Headphone Amp.
http://www.headphoneamp.co.kr/bbs/zboard.php?id=diy_sijosae&no=226

 

[mikeks]

bscally,
My CCS collection means following link.

http://www.headphoneamp.co.kr/bbs/zboard.php?id=diy_sijosae&no=122

mikeks,
In No. 15 & 16, CCSs are not connected in series but in parallel.

As a matter of fact, the arrangements of figs. 11-16 are positive feedback networks...and cannot function as sources, or sinks thereof.....

 

[sijosae]

As a matter of fact, the arrangements of figs. 11-16 are positive feedback networks...and cannot function as sources, or sinks thereof.....

mikeks,
In real situation, CCS No. 12 works very well.
It shows excellant result.
http://www.headphoneamp.co.kr/bbs/zboard.php?id=diy_sijosae&no=211

Here are photos of this CCS module.
http://www.headphoneamp.co.kr/bbs/zboard.php?id=diy_sijosae&no=136

 

[amplifierguru]

Hi Sijosae,

The No12 (I won't say your because it's been around for some time) LED/comp BJT CCS has the advantage of being a 2 terminal device, so what is it's impedance and BW, measured against it's extra complexity and what application can you see a worthwhile improvement in?

Cheers,
Greg

 

[sijosae]

amplifierguru,
As for impedance and BW, I have no data.
I'm sorry.