Current driven OPS?

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#21
Dave Zan said:
...the OPS is current driven rather than driven by a V source...
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BTW: what does this mean actually?
The OPS input impedance is changing so driving it with a current that is X times the input voltage signal is the goal?
Or you just mean it as the "output mode" of the VAS independent from the OPS load?
If so: a high current VAS and the it's output loaded to GND with a simple resistor isn't a good solution?

sgrossklass said:
It's a matter of impedance.
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And in this context these impedances mean dynamic, "delta" impedances, right?

vzaichenko said:
Because of D7...
This is a simple current mirror as well.
Now - we can make it multiplying current, if we use emitter resistors with different values.
Providing a rather linear current gain.
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And what makes this operation better and faster then amplifying voltage?
I mean at the input of the OPS high voltage (and so a voltage amplification at some point) is anavoidable.
What can be then the difference between a conventional voltage amplification and using current operations to achieve the same outcome?
 
#22
Some examples of Current driven output stages

* Bipolar output stages :

- Wim de Jager, Erik van der Ven, Ed van Tuyl, ELECTRONICS WORLD, December 1999 pp. 982 – 987

C31_Jager.gif


- Blomley's amp as mentionned.
A handy program to merge Gannaji's PDF files is PDFsam (

http://www.pdfsam.org/download-pdfsam-basic/ (previous version at bottom right of the page)

PDFsam Enhanced (recent version, I have not tested it yet)

* Mosfet output stages :
- James Strickland's Transnova amps.
 
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#23
A further reference is Hawksford's "Error Correction and Non-Switching Power Amplifier Output Stages" (Preprint 4492, Presented at 102nd AES Convention, March 1997).

The paper eludes to suitable power transistors in a footnote and is interestingly framed within a similar desire to Blomley to engineer a non-switching output stage.
 
#26
forr said:
Some examples of Current driven output...
Click to expand...

Thank you, the bipolar is new to me, I will read the article next trip to the library.
Are the authors associated with Technical University Delft?
It was some notes from a TUD course that was partly responsible to inspire this thread.
I have looked at the Transnova a while back but I will reexamine it.

Best wishes
David
 
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#36
Note that in Hawksford's 1981 report "Distortion Correction in Audio Power Amplifiers" he took (probably by mistake) some mathematical "liberties" that he later confessed to in his 1991 "Towards a Generalisation of Error Correction Amplifiers" as a result of negative feedback of another kind!
Funny.
 
#37
traderbam said:
Note that in Hawksford's 1981 report "Distortion Correction in Audio Power Amplifiers" he took (probably by mistake) some mathematical "liberties" that he later confessed to...
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Special Thank you for that😉
I had noticed "issues" in Hawksford Error Correction but was hesitant to contradict a famous author until I had a very firm case.
I don't want to write a detailed critique if it's already old news.

Best wishes
David
 
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