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Old 9th March 2012, 01:45 AM   #1
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Default Pros and Cons of current feedback amplifier.

Hi Friends,
I took some couple of month to develop no overall feedback amplifier, but it is so hard to do it.
Hardly to specify the voltage gain and gain matching between L and R channel.
I saw Moon Evolution series power amplifiers with claimed that no overall feedback with shorter signal path. Simaudio MOON W-8 Dual-Mono Power Amplifier

Now I have done a current feedback amplifier design, but not so sure how it sounding.
Can you please share what the advantage of current feedback circuit?

My new integrate amplifier is like below.

Buffer Amp-->Low impedance volume control-->Voltage gain-->Current based amplifier.
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Old 14th March 2013, 10:59 AM   #2
lineup is offline lineup  Sweden
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What is good in CFA is the slewrate.
What is less good is sensitive to the power supply. Lower PSRR.
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Old 14th March 2013, 11:11 AM   #3
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Quote:
Originally Posted by smithomo View Post
Now I have done a current feedback amplifier design, but not so sure how it sounding.
Can you please share what the advantage of current feedback circuit?
Some of the older chipamps are current feedback and they're reputed to sound better than the more modern VFB ones. Thinking here specifically of TDA2003A and TDA2009. I tend to prefer the sound of CFB opamps to VFB ones. LM6172 though is VFB and normally sounds fine - internally though its CFB architecture.
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Old 14th March 2013, 11:17 AM   #4
AndrewT is offline AndrewT  Scotland
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Maybe worth following up these Members thoughts.
Audio Power Amplifier Design book- Douglas Self wants your opinions
and
Audio Power Amplifier Design book- Douglas Self wants your opinions
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Old 15th March 2013, 11:30 AM   #5
hahfran is offline hahfran  Germany
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Quote:
Originally Posted by smithomo View Post
Hi Friends,
I took some couple of month to develop no overall feedback amplifier, but it is so hard to do it.
Hardly to specify the voltage gain and gain matching between L and R channel.
I saw Moon Evolution series power amplifiers with claimed that no overall feedback with shorter signal path. Simaudio MOON W-8 Dual-Mono Power Amplifier

Now I have done a current feedback amplifier design, but not so sure how it sounding.
Can you please share what the advantage of current feedback circuit?

My new integrate amplifier is like below.

Buffer Amp-->Low impedance volume control-->Voltage gain-->Current based amplifier.
Very simple. BJTs are current amplifiers and so to speak by their very nature
( that is the physics of semiconductors) these feel good if they just do current amplification that is current in current out. So it is just "natural" to employ current feedback because there are two "current to voltage transformations" less involved in the loop.
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Old 15th March 2013, 11:57 AM   #6
dadod is offline dadod  Croatia
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Quote:
Originally Posted by hahfran View Post
Very simple. BJTs are current amplifiers and so to speak by their very nature
( that is the physics of semiconductors) these feel good if they just do current amplification that is current in current out. So it is just "natural" to employ current feedback because there are two "current to voltage transformations" less involved in the loop.
Everything is not so simple!
extract from wikipedia:
In analog circuit design, the current-control view is sometimes used because it is approximately linear. That is, the collector current is approximately times the base current. Some basic circuits can be designed by assuming that the emitter–base voltage is approximately constant, and that collector current is beta times the base current. However, to accurately and reliably design production BJT circuits, the voltage-control (for example, Ebers–Moll) model is required.[1] The voltage-control model requires an exponential function to be taken into account, but when it is linearized such that the transistor can be modelled as a transconductance, as in the Ebers–Moll model, design for circuits such as differential amplifiers again becomes a mostly linear problem, so the voltage-control view is often preferred. For translinear circuits, in which the exponential I–V curve is key to the operation, the transistors are usually modelled as voltage controlled with transconductance proportional to collector current. In general, transistor level circuit design is performed using SPICE or a comparable analog circuit simulator, so model complexity is usually not of much concern to the designer.
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Old 15th March 2013, 12:37 PM   #7
hahfran is offline hahfran  Germany
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That entirely misses the point
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Old 15th March 2013, 01:05 PM   #8
dadod is offline dadod  Croatia
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Originally Posted by hahfran View Post
That entirely misses the point
I am sorry that you don't get it.
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Old 15th March 2013, 02:06 PM   #9
JMFahey is offline JMFahey  Argentina
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Quote:
Some of the older chipamps are current feedback and they're reputed to sound better than the more modern VFB ones. Thinking here specifically of TDA2003A
Who says TDA2003 is current feedback?
The typical low value resistor network shown provides Voltage fedback.
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Old 15th March 2013, 02:15 PM   #10
Waly is offline Waly  United Kingdom
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Quote:
Originally Posted by JMFahey View Post
Who says TDA2003 is current feedback?
The schematic, page 2 in the ST datasheet.
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