Can some one give me a schematic on a current source, adjustable around 3 A.

[AKSA]

Hi Michael,

2nd Edition, page 74, Chapter 2, 'Deficiencies of Current Sources'.

This covers most of the stuff you've brought up.

I couldn't find much on impedance at the drain/collector looking into the CCS, so when I find my Boylstad and Nashevsky (which appears to have grown legs and gone walkabout dammit!) I will study the equations which permit accurate computation of this effect. But I do know that the value of the emitter/source resistor figures prominently in this calculation.

I know your intentions are purely academic, Michael, and I respect that. There are many instances in instrumentation where a very accurate CCS is required, but by and large, and particularly in light of the highly erratic loads presented by dynamic speakers and even the following stages, these CCS refinements are probably not too essential for audio.

A cursory examination of NP's current sources indicates not too much obsession with accuracy; he knows that something with low component count and moderate performance is all that is necessary.

Cheers,

Hugh

 

[PMA]

Once again, and I've said this to your friend PMA, there is no need for negative, patronising tones when a novice asks for opinions/circuits. Strangely enough, Pavel, people do not see you as an individual, but rather as an ambassador for your country. A presence on this forum is a dynamic, world view of your nation, as others never see us as we see ourselves.......

Cheers,

Hugh

Hugh,

this is a great chance and challenge for you.
Do not hesitate and keep it firmly.

Cheers,
Pavel

 

[Ultima Thule]

Hi Hugh,

Thanks for understanding my intentions.
yes, page 74, not strange I wondered for a while why they covered almost only current mirrors..

Very appreciated if you will find something to report from your other books.

I agree with your point regarding CCS's in audio circuits, while I feel appealed to complex circuitries I also strive for the philosophy of keeping the device count in signal path at a minimum and the complexity builds up more by supporting surrounding components, in practice we may perhaps have some different views, but at the same time I think "simple is beautiful" and have started by time see the beauty by it's own and appreciate it's qualities too, at least theoretically.

BTW did you find your FET CCS with 2 LED's and 0,22(?) Ohm RS to be optimal or have you tried also with higher gate voltage/larger RS, like 3 or more LED's?

Regarding CCS's for the LTP, actually I have had a "heroic" idea trying to replace the CCS with a resistor of say 500 kOhm running from a voltage giving a corresponding 2mA, compare this to a CCS transistors Cre of only 2pF corresponding to approx 320k "only" at 250 kHz, well thats all for the crazy part for now...

Cheers Michael