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Old 14th March 2011, 01:33 PM   #1
GregH2 is offline GregH2  Australia
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Default Constant Current Pros and Cons

Hello All,

Please see attached figure below. We have here two configurations of a source follower amplifer running in Class A with a CCS load.

The configuration on the right passes all current drawn from the power supply through a CCS, meaning the current draw is constant. There is no direct route from the PS through the speaker to ground. It has to go through the CCS first (thanks AndrewT).

The configuration on the left is free to pass whatever it can through the load.

So, what are the pros and cons of each configuration?? Clearly a constant current draw will make things easier on the power supply and probably cause less supply induced noise. However, will the constant current version be able to supply enough current to supply the speaker adequately and provide good extension at low frequencies or when the impedance drops? Might this reduce bass where one assumes the more current the better?

Any thoughts on the relative merits of each configuration would be appreciated.

Regards,

Greg.
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Old 14th March 2011, 01:48 PM   #2
lineup is offline lineup  Sweden
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TYpe A is to prefer.
IT has better PSSR, power supply rejection ratio.
Given input 0V is at ground level

Type B will put any ripple from V+ onto speaker.
Type A will not.
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Old 14th March 2011, 02:30 PM   #3
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Agreed. Because input is not also common to V+, Type B is worse.

Search: Loftin White , and look for versions without a cathode bypass to GND.
Darius and Sheldon seem to know whats going on with that...
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Old 15th March 2011, 09:41 AM   #4
GregH2 is offline GregH2  Australia
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Ok thanks guys. Interesting. What about with a regulated supply?
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Old 15th March 2011, 10:27 AM   #5
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I guess the variant B in the post no1 is shown not correctly, I would propose the following schematics for discussion
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Old 15th March 2011, 11:07 AM   #6
forr is offline forr  France
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I reminds me Ciuffioli's mosfet follower, it uses a capacitive multiplier power supply.

Click the image to open in full size.

I call it a shunt amplifier.
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Old 15th March 2011, 11:59 AM   #7
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Quote:
Originally Posted by forr View Post
I reminds me Ciuffioli's mosfet follower, it uses a capacitive multiplier power supply. I call it a shunt amplifier.
Did you eventually come to some conclusions about merits of the shunt amp?
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Old 15th March 2011, 12:31 PM   #8
GregH2 is offline GregH2  Australia
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Hmm, yes a much better way to do it. Really interesting concept for me in my pursuit of low distortion zero feedback circuits.

Thanks for the design ideas. Really appreciate it.
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Old 15th March 2011, 12:38 PM   #9
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I remember that article can you post the rest if it or email it to me please?
I have been doing some designing in circuit maker on class a power amps lately. jer
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Old 15th March 2011, 12:53 PM   #10
forr is offline forr  France
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Quote:
Originally Posted by geraldfryjr View Post
I remember that article can you post the rest if it or email it to me please?
I have been doing some designing in circuit maker on class a power amps lately. jer
Hi, you'll find it here :

Andrea Ciuffoli - Documentation page
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