It was Mark Alexander.
I have used CFB amplifiers in RF applications -- from Intersil and Texas Instruments. Ron Mancini has a good note in the current edition of EDN --> www.ednmag.com -- you have to be quite careful of layout with CFB opamps due to the very high slew rate.
The SSM2131 is no longer in production, shouldn't stop you, however.
The IGBT's of this approximate description are readily available from a number of sources, but some of the other values may have to change.
No, I haven't built this particular amplifier, but had the application note in my files.
I have used CFB amplifiers in RF applications -- from Intersil and Texas Instruments. Ron Mancini has a good note in the current edition of EDN --> www.ednmag.com -- you have to be quite careful of layout with CFB opamps due to the very high slew rate.
The SSM2131 is no longer in production, shouldn't stop you, however.
The IGBT's of this approximate description are readily available from a number of sources, but some of the other values may have to change.
No, I haven't built this particular amplifier, but had the application note in my files.
I have help a friend long time ago with a power amp but I don't remember which opamp we used. The output stage was mosfets.
I have designed a headphone amp based on the idea.
http://home.swipnet.se/~w-50719/hifi/qrv03
For those who wonders, yes, I have a written permission from Analog Devices to use their patented design.
Ampslab has also an Alexander amp
http://ampslab.com/bi300_schematics.htm
The danish magazine High-Fidelity had an article series together with pcb's. Could it have been 1995? Some dane maybe can enlighten me.
If you want a better quality of the app note than from Analog Devices, it can be found here.
I have designed a headphone amp based on the idea.
http://home.swipnet.se/~w-50719/hifi/qrv03
For those who wonders, yes, I have a written permission from Analog Devices to use their patented design.
Ampslab has also an Alexander amp
http://ampslab.com/bi300_schematics.htm
The danish magazine High-Fidelity had an article series together with pcb's. Could it have been 1995? Some dane maybe can enlighten me.
If you want a better quality of the app note than from Analog Devices, it can be found here.
The design is not dependent of any special kind of part. The opamp should have certain properties like rather low power consumption and high output current. Any output stage can be used.Prasanna said:
They don't know what it is... I think. Fear for the unknown but I don't fear current feedback if you check what I have done so far.Prasanna said:Why DIY community is scared of current feedback.
SonnyA doesn't fear current feedback either.
http://mirand.dk
The design is not dependent of any special kind of part. The opamp should have certai
Great pleasure to see design based on same principle. This has boosted my moral :
If I design my own amp using same CF principle then will it be violation of patenet of anaolog Devices. P-A please clear
Can anybody discuss the Do's & Don'ts in building current feedback Amps.
Great pleasure to see design based on same principle. This has boosted my moral :
If I design my own amp using same CF principle then will it be violation of patenet of anaolog Devices. P-A please clear
Can anybody discuss the Do's & Don'ts in building current feedback Amps.
Shubham Prasanna,
Nice to see you,
If you design your current feedback amp with Discrete Frontend instead of using opamps, then its very easy to stabalize and give you better understanding, besides its very easy....I have also build it using N-channel Mosfets at the output......
Shubhkamnayein,
K a n w a r
Nice to see you,
If you design your current feedback amp with Discrete Frontend instead of using opamps, then its very easy to stabalize and give you better understanding, besides its very easy....I have also build it using N-channel Mosfets at the output......
Shubhkamnayein,
K a n w a r
Re: The design is not dependent of any special kind of part. The opamp should have certai
Second, if you don't plan to make fully working commercial products, then you can relax.
First it's a US patent.Prasanna said:If I design my own amp using same CF principle then will it be violation of patenet of anaolog Devices. P-A please clear
Second, if you don't plan to make fully working commercial products, then you can relax.
Re: The design is not dependent of any special kind of part. The opamp should have certai
Suggestion: Search here and use "current feedback". Lot's of threads will appear.
Since you ask, there are a couple real important "don't's" and this is concerning the feedback.
Here are two reference sources:
http://www-s.ti.com/sc/psheets/slod006b/slod006b.pdf
http://www.analog.com/library/analogDialogue/archives/39-05/op_amp_applications_handbook.html
Check also my designs, QRV-03, QRV-07, QRV-08, all current feedback with excellent performance. The QRV-08 design is measured to 0.00046% distortion.
There is much inforamtion out there about the subject. Walt Jung and others have written good stuff.Prasanna said:Can anybody discuss the Do's & Don'ts in building current feedback Amps.
Suggestion: Search here and use "current feedback". Lot's of threads will appear.
Since you ask, there are a couple real important "don't's" and this is concerning the feedback.
Here are two reference sources:
http://www-s.ti.com/sc/psheets/slod006b/slod006b.pdf
http://www.analog.com/library/analogDialogue/archives/39-05/op_amp_applications_handbook.html
Check also my designs, QRV-03, QRV-07, QRV-08, all current feedback with excellent performance. The QRV-08 design is measured to 0.00046% distortion.
The article ran over a few issues of High Fidelity in 1994 and 1995. IIRC the design was pretty much straight out of the app. note. with the author's own PCB-layout.peranders said:
/U.
EDIT: The author received permission from AN to manufacture and sell 75 sets of PCBs to the magazine's readers, but I believe the PCB artwork was published in the article.
If you design your current feedback amp with Discrete Frontend instead of using opamp
Mr. Kanwar,
I have analyzed many CF designs with Descrete Frontend However, if you consider the techical data you will find that the Op-amp front-end designs give lower distortion figures, widest power bandwidth
Take an example, The Compact Power Amp from T. Giesberts published in Elektor magazine in 1997 uses descrete front-end.
It's Power bandwidth is 470Khz whereas the two designs with op-amp I saw give around 1Mhz. Nevertheless Mr Mark Alexander gave the formula to calculate powerbandwidth.
The distortion figures of op-amp designs are remarkabaly low So I think to design the CF amp with op-amp front-end Of course,
I aware it may pose serious stabilty issues.
How about the idea of using descete op-amp instead of monolitic one ? Because a well designed descrete op-amp out-perform a monolithic one. Will anybody opine ?
Mr. Kanwar,
I have analyzed many CF designs with Descrete Frontend However, if you consider the techical data you will find that the Op-amp front-end designs give lower distortion figures, widest power bandwidth
Take an example, The Compact Power Amp from T. Giesberts published in Elektor magazine in 1997 uses descrete front-end.
It's Power bandwidth is 470Khz whereas the two designs with op-amp I saw give around 1Mhz. Nevertheless Mr Mark Alexander gave the formula to calculate powerbandwidth.
The distortion figures of op-amp designs are remarkabaly low
So I think to design the CF amp with op-amp front-end Of course,I aware it may pose serious stabilty issues.
How about the idea of using descete op-amp instead of monolitic one ?
Because a well designed descrete op-amp out-perform a monolithic one. Will anybody opine ?Check also my designs, QRV-03, QRV-07, QRV-08, all current feedback with excellent performance. The QRV-08 design is measured to 0.00046% distortion.
Thanks Mr Per-Anders for referencing very good documentation on op-amps& feedback techniques.
Mr. Per-Anders can you elaborate how these distortion figures are measured ? Under test-conditions(dummy resistive load) or
in Live environment ?
My one more observation is that in the design by Mark Alexander
the slew rate of input stage op-amp SSM-2131 is just 40v whereas the power amp gives slew rate of 200v. Is it possible to attain higher slew-rate of any amp than that of it's any stage.
The distortion measurement is done by some guy from the former east, but my mind is a bit foggy now. Maybe someone remember in which forum that was? Ha had an extremely good soundcard.
The slewrate is amplified equally much as the "gain" in opamp. If the gain is four (AN-211) the slewrate will increase four times.
As yop may have seen by now there are also drawbacks. You can't use a current feedback amp as an intergrator. You can't choose any value you like for the feedback.
The slewrate is amplified equally much as the "gain" in opamp. If the gain is four (AN-211) the slewrate will increase four times.
As yop may have seen by now there are also drawbacks. You can't use a current feedback amp as an intergrator. You can't choose any value you like for the feedback.
alexander current feedback amplifier
I build this amplifier at time is was puplished in the Analog Devices Reference manual (1994 or so) and I used the original IGBT output devices. My amplifier is yielding 140 watts per channel into 5 ohm. More details on http://www.wdehaan.demon.nl/various/alexcurrentfb/index.html
Wim/NL
I build this amplifier at time is was puplished in the Analog Devices Reference manual (1994 or so) and I used the original IGBT output devices. My amplifier is yielding 140 watts per channel into 5 ohm. More details on http://www.wdehaan.demon.nl/various/alexcurrentfb/index.html
Wim/NL
Only at 1 kHz but due to it's speed you'll have good figures high up. Just check just about any current feedback amp, similar performance.
Search at Texas Instruments, Linear Tech and Analog Devices. Lot's of info there.
Check for instance the TPA6120 (my QRV-07) and it's figures. Sounds equally as it's figures.
Some IC's have 0.03% dist at 5-10 MHz even! Check Analog Devices!
Search at Texas Instruments, Linear Tech and Analog Devices. Lot's of info there.
Check for instance the TPA6120 (my QRV-07) and it's figures. Sounds equally as it's figures.
Some IC's have 0.03% dist at 5-10 MHz even! Check Analog Devices!
alexander current feedback amplifier
As mentioned I build this amp back in 1993. The words on optimal TIM and DIM distirtion figures and the patented circuit got my attention and gave a save feeling it was a great design.
At time it was very difficult to source or even buy the IGBT's. I got them from the manufacterer themself. The datasheet mentions O and Y types, at that time everything was sold as is; meaning you didn't know which device you got. So for example the positive side ran at 200 mA and the negative side at 900 milliamps or so, because of the different Ugs voltage. In 1993 or so supplier mentioned it on the divece itself. Other problem is the latch up current, the device acts like a thyristor and will destroy itself if the Ugs is above the 12V or so.
I doubt if the designer ever build the amplifier using the IGBT's. The original design is using a strange combination of an IXYS power mosfet (at that time out of production because they were very unreliable) and an IRF power mosfet. This also because the IGBT's are very sensitive in thermal run-a-way; extra precautions are mandatory. I did try also the common audio power mosfets like the 2SJ118 and so as well and this works perfectly.
Sound of this amp using the IGBTs is very dissapointing. Played loud or soft it can't even get close to my 12Watt PP 6336A based tube amplifier. Compared to a 25 watt Japanes solid state design (I called it the MJ Amp as can be found on my website) it fails also.
It terms of dynamics it fails to do what it is written in the article.
My advice is to forget about this amplifier design and to focus on some other design.
I used high grade BH PSU capacitors with 300VA transfomers per channel, Caddock MP816 emitter resistors, the feedback resistor is also a Caddock MP816, silvermica caps, Dale RN55 resistors, the SSM2131 opamp, throughout selected transistors, WBT connectors, audio grade wiring and so on. Boards are double sided and custom made.
Toshiba stopped producing the IGBTs already some long time ago. Even Threshold and Counterpoint stopped producing their amps using these IGBTS already shortly after their release (back in the 90's)
Wim
http://
As mentioned I build this amp back in 1993. The words on optimal TIM and DIM distirtion figures and the patented circuit got my attention and gave a save feeling it was a great design.
At time it was very difficult to source or even buy the IGBT's. I got them from the manufacterer themself. The datasheet mentions O and Y types, at that time everything was sold as is; meaning you didn't know which device you got. So for example the positive side ran at 200 mA and the negative side at 900 milliamps or so, because of the different Ugs voltage. In 1993 or so supplier mentioned it on the divece itself. Other problem is the latch up current, the device acts like a thyristor and will destroy itself if the Ugs is above the 12V or so.
I doubt if the designer ever build the amplifier using the IGBT's. The original design is using a strange combination of an IXYS power mosfet (at that time out of production because they were very unreliable) and an IRF power mosfet. This also because the IGBT's are very sensitive in thermal run-a-way; extra precautions are mandatory. I did try also the common audio power mosfets like the 2SJ118 and so as well and this works perfectly.
Sound of this amp using the IGBTs is very dissapointing. Played loud or soft it can't even get close to my 12Watt PP 6336A based tube amplifier. Compared to a 25 watt Japanes solid state design (I called it the MJ Amp as can be found on my website) it fails also.
It terms of dynamics it fails to do what it is written in the article.
My advice is to forget about this amplifier design and to focus on some other design.
I used high grade BH PSU capacitors with 300VA transfomers per channel, Caddock MP816 emitter resistors, the feedback resistor is also a Caddock MP816, silvermica caps, Dale RN55 resistors, the SSM2131 opamp, throughout selected transistors, WBT connectors, audio grade wiring and so on. Boards are double sided and custom made.
Toshiba stopped producing the IGBTs already some long time ago. Even Threshold and Counterpoint stopped producing their amps using these IGBTS already shortly after their release (back in the 90's)
Wim
http://
Have a look at www.scopeboy.com/amp1.html
This is a version with high-current lateral output MOSFETs.
This is a version with high-current lateral output MOSFETs.
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