const. voltage & const. current on output FET ?
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Christer
diyAudio Member

Join Date: Sep 2002
Location: Sweden
Re: Re: Re: Stasis^2

Quote:
 Originally posted by Steven more or less constant
And there came the magic words.

But OK, I understand now from your explanation of Stasis what you might mean in practice.

 26th November 2005, 01:55 PM #12 Ultima Thule   diyAudio Member     Join Date: Jan 2004 Location: Finland Hi Bernard, I have a bit difficult to grasp what you have in mind, it would help if you have a schematic to show. Constant voltage and current is equal to constant power, how can you have that on the output transistor if you want to play music which is not "constant"... Cheers Michael
Steven
diyAudio Member

Join Date: Oct 2003
Location: The Netherlands
Constans (a different Stasis)

As this thread is about constant voltage and current output devices (BJT or FET doesn't matter), I present an idea that I had put on paper more than a year ago, but had no time to do something with.

I just have put it into Circuitmaker now to see whether it actually works as anticipated, and it does.

It shows a single ended output stage without voltage gain. Q1 is an emitter follower, but could be a source follower too. The current source in its collector determines the constant current of Q1. If the load current through R2 changes, the current through Q1 starts to change too, but this forces a difference current through Q3. Q3 drives Q2 and the current through Q2 will change in such a way that the output current can be delivered while the current through Q1 remains constant.
The voltage across Q1 is also constant. Because of Q3, the collector of Q1 is approximately at the same voltage as its base, which is one Vbe higher than its emitter. So there is a constant voltage of approximately 0.8V across Q1. This can be made more by e.g. adding a diode into the emitter of Q3.

For now I call this circuit Constans, which means more or less the same as Stasis, but now in Latin.

Steven
Attached Images
 circuit.gif (3.2 KB, 746 views)
__________________
The Analog Art shows no sign of yielding to the Dodo's fate. The emergence and maturation of monolithic processing finesse has perhaps lagged a bit behind the growth of the Binary Business. But whereas digital precision is forever bounded by bits, there is no limit excepting Universal Hiss to the ultimate accuracy and functional variety of simple analog circuits. - Barry Gilbert, 1973

Steven
diyAudio Member

Join Date: Oct 2003
Location: The Netherlands
Constans waves

The picture below shows the current waveforms. It is clear that the collector current of Q1 is constant (green line). The output current is shown in blue, this is the load current. Never mind the sign, that is something of the simulator; my simulator likes negative currents.
Yellow shows the collector current of Q2. It is clear that the modulation of Q2 is causing the ability to source current into the load or sink current from the load.
The important thing is that the output voltage is determined by Q1 and not Q2. The performance Q1 is crucial and Q1 has an easy life with its fixed collector current of 2A in this example and only 0.8V across it. Not even 2W of dissipation!

Steven
Attached Images
 waves current.gif (5.7 KB, 516 views)
__________________
The Analog Art shows no sign of yielding to the Dodo's fate. The emergence and maturation of monolithic processing finesse has perhaps lagged a bit behind the growth of the Binary Business. But whereas digital precision is forever bounded by bits, there is no limit excepting Universal Hiss to the ultimate accuracy and functional variety of simple analog circuits. - Barry Gilbert, 1973

Steven
diyAudio Member

Join Date: Oct 2003
Location: The Netherlands
Constans voltage waveforms

More waveforms, now voltage.
Green is the collector voltage of Q1, yellow is the emitter voltage of Q1 and blue is the difference, which is constant.

Steven
Attached Images
 waves voltage.gif (5.7 KB, 481 views)
__________________
The Analog Art shows no sign of yielding to the Dodo's fate. The emergence and maturation of monolithic processing finesse has perhaps lagged a bit behind the growth of the Binary Business. But whereas digital precision is forever bounded by bits, there is no limit excepting Universal Hiss to the ultimate accuracy and functional variety of simple analog circuits. - Barry Gilbert, 1973

 26th November 2005, 02:38 PM #16 lumanauw   diyAudio Moderator Emeritus     Join Date: Oct 2002 Location: Bandung Hi, Steven, You give me a homework with 3 post above This is not about your cct, but about Peufeu "Memory Distortion". It seems his concept is also constant voltage+constant current. What do you think about Memory distortion, is it really exist? Or it performs better because the voltage and current is held constant?
Bernhard
diyAudio Member

Join Date: Apr 2002
Location: Munich
Re: Re: Re: Stasis^2

Quote:
 Originally posted by Steven Nelson used cascoding to keep the voltage more stable and Sziklai output pairs to keep the current through the driver transistors more stable (in a Sziklai pair the driver controls the output).
The driver is the output ? Means Stasis output = constant current and constant voltage ?

Bernhard
diyAudio Member

Join Date: Apr 2002
Location: Munich
Re: Constans waves

Quote:
 Originally posted by Steven Q1 has an easy life with its fixed collector current of 2A in this example and only 0.8V across it. Not even 2W of dissipation!
As you mention it, this nice side effect means one can live with one gain device and there is no need for matching and no source of additional distortion due to mismatch.

I have a whole lot of ideas but lack a little bit of understanding the very basics as there are current mirrors & Sziklai pairs and the like.

Any nice website where those stuff is explained ?

 26th November 2005, 03:01 PM #19 Bernhard   diyAudio Member     Join Date: Apr 2002 Location: Munich I have to draw a schematic because I have implemented it in my distortion killer schematic and it is a little confusing to look at it. Basically the load current is sensed and the CCS current is corrected so that the gain device current remains constant. IMHO it is not important to holt I and V absolutely stable, hopefully minimized current swing and Vsd variation will result in reduced distortion.
 26th November 2005, 03:04 PM #20 lumanauw   diyAudio Moderator Emeritus     Join Date: Oct 2002 Location: Bandung Hi, Steven, I think I got a slight picture how it works. If this can have a nick name for "Constants", I would call it "SLH". John Lindsley Hood have "JLH", Nelson Pass have "PLH". This should be called "SLH" (S=Steven)

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