Output stages with gain Enhance Slew rate

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#141
Re: Endless loops do me no good.

Sawzall said:

MikeK, to look at it another way, if you had the driver stage that had the 100 v/us, and the output stage was our humble emitter follower with its less than 1 gain. Would the amp not still have roughly the same slew rate without the stabilty issues that outputs with gain can have?
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100V/us...with unity gain output stage rather difficult......if linearity is also to be of the first order...its possible however..

...400v/uS whole different order of things here....you would need to run your gain block in class AB...not elegant...in my view anyway...

But....as you may have noticed, i specifically recomended that the extra gain be generated before the unity gain output stage......by a complementary wilson mirror...
its parasitic capacitances are bootstrapped, making it easier to stabilise than a raw common emmiter stage at the output...

so...your concerns about instability in the output stage due to the extra gain are misplaced....
 
#142
traderbam said:
Lots of things have a "voltage transfer" close to unity into a loudspeaker load. Like a coil of wire or a relay or a forward-biased diode. Would you want to listen to your favourite musice through a forward biased diode?

I feel compelled to douse the slew rate debacle. For most loudness of music with typically efficient speakers, not much more than 5V/us is needed. We are debating a red herring.
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...not if your mobile 'phone goes off.....
 
#145
Re: Re: Re: Re: Re: Re: Slew rate etc

peranders said:

The MCP amp is a blueprint of the Alexander amp and yes, very much current feedback. The current comes from the current consumption of the opamp.
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peranders said:
I'm not sure what MCP is but I refered to the link under and Fred is right, the opamp is feedbacked conventionally but the overall feedback is about current.

The Marantz amp is also very much current feedback and the design is by the schoolbook.

Mike, if you don't agree on this I'll stop this yes-no war here.
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see:

http://www.anasoft.co.uk/EE/currentfeedbackmyth/currentfeedbackmyth.html
 
#146
traderbam said:
Lots of things have a "voltage transfer" close to unity into a loudspeaker load. Like a coil of wire or a relay or a forward-biased diode. Would you want to listen to your favourite musice through a forward biased diode?

I feel compelled to douse the slew rate debacle. For most loudness of music with typically efficient speakers, not much more than 5V/us is needed. We are debating a red herring.
Click to expand...


mikek said:



...not if your mobile 'phone goes off.....
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traderbam said:

This statement just about sums up your capabilities as a designer. Still, at least the chairs on the deck will be tidy as the ship goes down.
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So...does your summery apply to Mr. Jonathan Carr?:nod:

http://diyaudio.com/forums/showthread.php?postid=205867#post205867
 
#147
Wilson current mirror for gain?

Mike,

you said somewhere you propose to use a complementary Wilson mirror bias into class A to achieve the gain prior to the output stage proper. I have tried to find an actual schematic example in this thread, but gave up after re-reading half a dozen pages that contain mostly tedious fighting. Can you point me to an example?

If it was in the Electronics World paper, I erased that inadvertently. Would you mind resending?

Thanks,

Eric
 
#148
Re: Wilson current mirror for gain?

capslock said:
Mike,

you said somewhere you propose to use a complementary Wilson mirror bias into class A to achieve the gain prior to the output stage proper. I have tried to find an actual schematic example in this thread, but gave up after re-reading half a dozen pages that contain mostly tedious fighting. Can you point me to an example?

If it was in the Electronics World paper, I erased that inadvertently. Would you mind resending?

Thanks,

Eric
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no wasn't in EW paper...for an example, see:


http://diyaudio.com/forums/showthread.php?postid=192255#post192255
 
#149
Folks, I don't know whether I can help here, but: Please keep the slew rate above 50V/us. Trust me.
A follower can be a problem with difficult loads, because it has phase shift at very high frequencies. Still, a follower is the best compromise for a power amp.
 
#152
john curl said:
Folks, I don't know whether I can help here, but: Please keep the slew rate above 50V/us. Trust me.
A follower can be a problem with difficult loads, because it has phase shift at very high frequencies. Still, a follower is the best compromise for a power amp.
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I have also a good feeling about speedy amps but the slew rate number must be put in relation to the output power.
 
#153
"quote:
Originally posted by john curl
Please keep the slew rate above 50V/us.



Why?"

Jung suggests 0.5V/µS per peak volt of output, with a maximum of 2V/µS.

A typical 100W/8R amplifier has rails of ±55V (Adcom GFA545).

This would suggest a minimum of 28V/µS by Jung, john curl's recommendation looks to be halfway between the minimum and maximum of Jung.
 
#159
djk said:
"quote:
Originally posted by john curl
Please keep the slew rate above 50V/us.



Why?"

Jung suggests 0.5V/µS per peak volt of output, with a maximum of 2V/µS.

A typical 100W/8R amplifier has rails of ±55V (Adcom GFA545).

This would suggest a minimum of 28V/µS by Jung, john curl's recommendation looks to be halfway between the minimum and maximum of Jung.
Click to expand...

Jung is quite right (at maximum), Curl does not show any relation to output power (or voltage swing).
 
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