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Old 12th January 2006, 02:46 PM   #1
X.G. is offline X.G.  China
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Default new idea for power amp

the schematic is designed by my friend Locky_Z.he ask me to post here....

this is his post of the Hifidiy.net


http://www.hifidiy.net/dispbbs.asp?b...D=21315&skin=0

it is current output amp.the output current IL=Vin * Rc / (Rsc * R6)




any comment?

Click the image to open in full size.
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Old 12th January 2006, 04:57 PM   #2
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It is a very original idea.

I have seen something like this, but WITH global feedback.
Distortion will be more like in some tube amplifiers. Not very low.

Maybe this amp can make good sound.
Very interesting idea.

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Old 12th January 2006, 07:20 PM   #3
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Default Re: new idea for power amp

Quote:
Originally posted by X.G.
the schematic is designed by my friend Locky_Z.he ask me to post here....

this is his post of the Hifidiy.net

http://www.hifidiy.net/dispbbs.asp?b...D=21315&skin=0

it is current output amp.the output current IL=Vin * Rc / (Rsc * R6)

any comment?
Why not simulate it but remember that current sources are non-ideal and they are different in real life. Spontaniously I feel that the opamp is working a comparator => won't work as an amplifier. Which were the supposed benefits? Just different?
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Old 12th January 2006, 08:15 PM   #4
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Intersting one and very unusual.

I think that current duty cycle may be an issue, namely both op-amp and output stage should have the same current duty cycle. Another words they should work in EXACTLY the same class. Otherwise differential amplifiers may get overdriven.
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Old 13th January 2006, 01:37 AM   #5
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Quote:
Which were the supposed benefits? Just different?
A friend of mine proposes similiar idea some time ago. The idea is to make an output stage that never turn off. Output stage is a current mirror+amplification with RC/RSC. And the current passing RC never turns off, it is the bias of the opamp at minimal point. So the current to the output RSC will also never turn off.

What is the value of R6 in the formula? Is it 470ohm?
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Old 13th January 2006, 01:57 AM   #6
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Default Re: Re: new idea for power amp

Quote:
Originally posted by peranders
Spontaniously I feel that the opamp is working a comparator => won't work as an amplifier.
The OP amp work as a unity gain follower and the output signal is obtained at the power supply pins , because the output of the OP Amp is loaded with a low value resistor.

The current trough the power pins will be equal to the current in the output resistor, more the currents of the others internal stages of the OP amp.

As the amp is not closed in a overall feedback loop, this kind of OP amp driver , will introduce many nonlinearitys.
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Old 13th January 2006, 06:43 AM   #7
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Default Re: Re: new idea for power amp

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Originally posted by peranders
Spontaniously I feel that the opamp is working a comparator => won't work as an amplifier.
...he, he, now I see the feedback of the opamp I must have been yesterday
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Old 13th January 2006, 07:14 AM   #8
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Driving current is too low = low SR, high distortion...
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Old 13th January 2006, 07:42 AM   #9
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Quote:
Originally posted by peranders
I must have been yesterday
Maybe you are today.

Can someone tell me which of the posted circuit is so surprising?
Output stages driven from opamp rails is 20 years old, especially MOSFET output stages.
Only difference i see is omiting the feedback, which does not look like a smart thing to me.
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Old 13th January 2006, 07:52 AM   #10
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Quote:
Originally posted by jacco vermeulen


Can someone tell me which of the posted circuit is so surprising?
Output stages driven from opamp rails is 20 years old, especially MOSFET output stages.
Only difference i see is omiting the feedback, which does not look like a smart thing to me.
The output stage use feedback of current ,that increase the output impedance , via the 0,22 Ohms drain resistors of the output Mosfets.
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