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Old 13th October 2009, 05:33 AM   #1701
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Now that we all realize that this is an example of a SIMPLE voltage regulator, why would we not go out of our way to make a complicated voltage regulator, with even better 'regulation'? To save time, I might point that a number of SIMPLE voltage regulators may protect circuits from each other, better than one master regulator feeding several channels of audio, doing different things.
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Old 13th October 2009, 10:41 AM   #1702
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Quote:
Originally Posted by Johnloudb View Post
Probably not enough feedback (no feedback)?

I don't see what your getting at Jan.

From Wiki ...



Joshua's regulator is a real one.
The wiki article makes a clear distinction between a regulator, where there is an error amp element that compares ref with output and REGULATES the pass element to maintain constant Vout, and an open loop circuit like Joshua's that does not regulate.

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Old 13th October 2009, 11:06 AM   #1703
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It actually does, though not very well. Vbe is an error voltage, and the follower has 100% voltage NFB. Boring issue.
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Old 13th October 2009, 01:36 PM   #1704
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Now, many of us have known about and designed more complex voltage regulators, why not use them in all audio circuits?
First there is the single added transistor as a gain element with a Zener reference, popular in the 1960's. This did lower the output impedance, but it could be noisy, due to the Zener diode noise.
Then there was the first series of IC based positive and negative regulators, the LM104 and the LM105, designed at National Semiconductor by Bob Widlar. These are long forgotten, but are really excellent regulators based on IC design. Many 'lab' supplies used them, back in the late 60's and early 70's. However, these were not to 3 terminal type regulators, popular today, but multi-pin designs that required and external output transistor. However, they did allow for RC bypassing of the Zener reference, and therefore can be very quiet. These designs also allowed for variable voltage adjust and other features. I have used a set of these power supplies since 1974, for many of my prototypes over the decades, and can still use these supplies today, if necessary.
Why then, are these devices 'obsolete' and 3 terminal devices mostly used today? The answer is: Convenience. 3 terminal devices are easier to wire up. Of course, tradeoffs follow, such as noise, etc. Still, 3 terminal devices can still be very useful.
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Old 13th October 2009, 01:37 PM   #1705
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Now, many of us have known about and designed more complex voltage regulators, why not use them in all audio circuits?
First there is the single added transistor as a gain element with a Zener reference, popular in the 1960's. This did lower the output impedance, but it could be noisy, due to the Zener diode noise.
Then there was the first series of IC based positive and negative regulators, the LM104 and the LM105, designed at National Semiconductor by Bob Widlar. These are long forgotten, but are really excellent regulators based on IC design. Many 'lab' supplies used them, back in the late 60's and early 70's. However, these were not to 3 terminal type regulators, popular today, but multi-pin designs that required and external output transistor. However, they did allow for RC bypassing of the Zener reference, and therefore can be very quiet. These designs also allowed for variable voltage adjust and other features. I have used a set of these power supplies since 1974, for many of my prototypes over the decades, and can still use these supplies today, if necessary.
Why then, are these devices 'obsolete' and 3 terminal devices mostly used today? The answer is: Convenience. 3 terminal devices are easier to wire up. Of course, tradeoffs follow, such as noise, etc. Still, 3 terminal devices can still be very useful.
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Old 13th October 2009, 01:41 PM   #1706
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Old 13th October 2009, 01:45 PM   #1707
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PMA, I have to start somewhere. Not everyone is as experienced and educated as you are, and many probably do not understand the 'advantages' of simple regulators in their audio designs, but I use them almost universally in everything that I design, including the Blowtorch preamp.
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Old 13th October 2009, 07:14 PM   #1708
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The simple linear voltage regulator has been shown. How can it be optimized or improved? There are several variations that are better in some design situations.
For example, what if you are making a small amplifier, without a regulated power supply, and you would like to efficiently regulate, or at least filter much of the residual ripple on the power supply from the input and voltage driver stages? Well, for a relatively efficient filter, you can remove the Zener diode completely, and make a Cap multiplier, instead. Carefully done, you can lose a minimum of volts across the output device so that you can smooth out the power supply ripple, yet lose only a volt or two. This is for when you have only a single +/- voltage supply for the whole amp. It works very well, and you will find it in most of my cheaper amp designs, for example. It also tracks the average DC output, so you don't lose anything, if you have different AC voltages, while simple fixed Zener regulators must have extra voltage drop in order to work properly with varying input voltages.
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Old 13th October 2009, 08:16 PM   #1709
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John, what you suggested exists in many regulators. An example of one of them is attached:
Attached Images
File Type: jpg TeddyReg-acc.jpg (12.9 KB, 270 views)
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Old 13th October 2009, 08:27 PM   #1710
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Too complex, Joshua. Proportion is important.
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