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Voltage
References

John Atwood

This
Issue

John Atwood is back (bless you John, my
fingers were getting tired from typing) with an excellent primer on
voltage references. He cover solid-state and vacuum tube voltage
references (gas tubes). This article is must-reading for anyone
interested in building a high voltage regulator.

The SRPP makes a second appearance. This time we will look into
using the SRPP topology in in power amplifiers, the possibility of
using a variation on this topology to drive a purely reactive load,
electrostatic speakers and headphones for example. Finally, we will
examine a new variation on the Mu Follower. And this month's Letters
covers the single-ended vs. push-pull aspect of the SRPP
circuit.
This month's design idea is a circuit that
strives to maintain a constant power dissipation for the output tube
in a Class A amplifier (single-ended or push-pull) regardless of
fluctuations in the wall voltage.
Remember, if you
have a request or suggestion of your own for either an article topic
or circuit explanation, please e-mail:

Editor

The heart of any voltage regulator is the voltage
reference. The output voltage stability and accuracy are no better
than the reference. Since this series of articles concentrates on
vacuum tube circuits, references for high-voltage supplies will be
covered here.
Some references can also serve as
regulators by themselves, i.e. they can supply significant power and
still maintain a constant voltage. Others, usually the more precise
ones, only maintain their specifications under very light loading,
and so must be connected to a regulator circuit to control
power.
References fall into two main categories: low
voltage and high voltage. Many good low voltage references have been
designed for the solid-state market. In order to use them with high
voltage regulators, their reference voltage needs to be greatly
scaled up, sometimes as much as 100 or 200, which can introduce
drift and errors, particularly in the simpler regulator circuits.
High voltage references are ones that are within a factor of two to
five of the output voltage. There are fewer high voltage references
available than low voltage ones, but their use can simplify the
regulator design.
The important specs for references
are: reference voltage, absolute accuracy, output impedance (in
two-terminal devices, this is called dynamic impedance) and the
temperature coefficient. The first three affect the reference's
integration into the regulator design. Variations in absolute
accuracy in both the reference and associated components are usually
handled by a trim pot. Unless carefully compensated, the temperature
coefficient can

In This
Issue

1
6
13
14
16

Voltage References
SRPP
Once Again
Correction
to May's SRPP Article
Design
Idea: Constant Power Amplifier
E-mail
Publishing
Information
Glossary
of Audio Terms
Glass-Ware.com
Articles
Classic
Magazine articles

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