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Old 26th February 2007, 01:50 AM   #61
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Quote:
Originally posted by mach1


In that case JA's reg and every other zener referenced example must be shunt regs because the zener string is the shunt reg.

pm
Only if the reg don't have an error amplifier.
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Old 26th February 2007, 02:49 AM   #62
mach1 is offline mach1  Australia
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Sorry, I remain unconvinced.

Even if we adopt your definition of a shunt reg:

Quote:
Only if the reg don't have an error amplifier.
The 10M45S contains an error amplifier.

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Old 26th February 2007, 03:28 AM   #63
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Quote:
Originally posted by mach1
Sorry, I remain unconvinced.

Even if we adopt your definition of a shunt reg:



The 10M45S contains an error amplifier.

pm
I suggest you to use your own definition if you feel it reflects better for you what is significant.
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Old 26th February 2007, 04:10 AM   #64
mach1 is offline mach1  Australia
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I am simply applying the conventionally accepted definition of what constitutes a shunt regulator.

Tubecad Journal V1 No5, July 1999 states:

Quote:
The principle of operation of a shunt regulator in AC terms is simple enough .......In DC terms: the power supply rail voltage is compared to a voltage reference and the idle current through the shunt regulator is varied to bring the power supply voltage in line with the reference.
In this regulator the idle current through the 'shunt element' (10M45S and voltage set resistors) is held constant. The mosfet is a simple series pass device with the 10M45s controlling gate voltage (just as the zeners controlled the gate voltage in JA's schematic). The current through the mosfet = current drawn by the device being powered plus the current sunk through the output resistor.

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Old 26th February 2007, 04:21 AM   #65
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Defenitely the shunt regulator from your Tubecad article is not comprehensive, it describes some variant of it. Shunt regulator strictly speaking means that the regulating element is parallel to the load (shunting it). Load may be an input of another regulator, when shunt regulator is a source of a reference voltage for it.

Anyway, I don't like such stamps that limit free flow of engineer's creative thinking. Do whatever you want to achieve an optimum depending on criteria given, that's it, no matter how somebody will call your end result.
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Old 4th April 2008, 10:47 AM   #66
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Default Series Mosfet regulator

Series Mosfet regulator Post #31

Hi John,
in your post #31 of this thread, you say:

<<I'm a little late to this thread, but thought you would be interested in what we do in the Artemis Labs preamps. Attached is a fragment of the schematic of the LA-1 line amp. It is the B+ regulator, for one channel. The zener diode reference string is shared between channels. The exact same circuit is used in the PH-1 and PL-1 phono preamps.>>

Could you, please, show how to drive on/off Q106 ?
since Ve is +160V.

Thanks

Roberto
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Old 4th April 2008, 04:08 PM   #67
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Default turning on Q106

Sorry for being a little late in getting back to you. Q106 has a 1k resistor from emitter to base to prevent leakage from turning it on. A 24K 3W resistor goes from the base to an SCR to ground. The SCR is triggered by a neon bulb time delay circuit. I wish I could send you the full schematic, but this design was done under contract with Artemis Labs, and I can't show the whole thing. The key aspect of the circuit is the 24K resistor that pulls the base of the PNP towards ground, thus turning it on.

- John Atwood
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Old 4th April 2008, 10:54 PM   #68
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I never really said thanks properly for all those magnificent contributions to this thread . . . so a belated thanks to all!

BTW, it seems to me that a Schmitt trigger could be arranged as a delay for turning on the zener (or other voltage reference) that drives the gate of the MOSFET. This would be an improvement over a simple C-R delay. In fact, the two in combination would be nice, giving an initial delay followed by a ramp-up.
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Old 5th April 2008, 08:13 AM   #69
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Thanks John,

what is the reason of using a neon, because of the pulse it would make when it reaches
the trigger voltage ?
Could you, please, point to a page where I can learn about neon based delay ?

Roberto
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Old 20th May 2011, 01:35 AM   #70
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I notice C2 in the Last PAS Regulator.

However in linear breif 47 it states:

"The zener impedance is low enough that no bypass capacitor is required
directly at the LM317 input. (In fact,no capacitor should be used here if the circuit is to survive an output short!) R3 limits short circuit current to 50 mA."

In addition there is no current limit resistor in the Last PAS Regulator. Does this leave it subject to destruction under excessive load conditions?
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