My guess is that the tweak circuit is placed at risk because of the higher quality capacitors and wider bandwidth solid-state devices used. On the other hand, the stodgy circuit benefits in terms of longevity from the slowness of the cheap IC and higher eternal impedance of the cheap capacitor. The reason is obvious enough: the cheap IC is less prone to oscillate at ultra high frequencies and less prone to latch up at turn-on. And the high ESR of the cheap capacitor works to limit the peak current rush through the IC's internal protection diodes. (The Nation Semiconductor's application sheet for the LM317 shows a high voltage regulator that holds an LM317 at its heart. The high voltage electrolytic capacitors used are seried with a small valued resistor. Removing these resistors usually results in a blown regulator.) If we plan on using high quality parts, then we must take more care in the design.


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Solid-State as DC Circuit Support

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Forward biased diodes in place of resistors

    The attempt here is to limit the use of solid-state devices to non-AC applications only. DC servos, voltage references, auto-bias circuits, and voltage limiters all come to mind as non-AC uses. Some will argue that a DC servo is in fact an AC application, which of course it is, if we include infrasonic frequencies in our definition of AC. What is meant by "non-AC application" is a circuit that that has minimal effect on the audible frequencies.

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