Crown DC-300A, Инструкция по эксплуатации, Страница: 28 / 42

APPLICATION NOTE NO. 1
V-l LIMITS OF A LOAD
Evaluating the V-l (volt-ampere) needs of a load: Many
loads exhibit large
(or energy storage),
which limits a power amplifier’s ability to deliver a
maximum power. If a load stores energy, which in turn
flows back into the amplifier, it is clear that the max-
imum power efficiency of the system is not being
achieved. Power that flows back into a linear amplifier
must necessarily be dissipated in the form of heat. A
pure reactance is not capable of dissipating any power;
therefore to drive such a load would only cause power
amplifier heating.
In practice all loads exhibit some energy dissipation
however large their energy storage characteristics may
be. The ideal coupling to any load is one that optimizes
the desired dissipation component while minimizing the
reactive or stored-energy component that is seen by
the amplifier’s output terminals.
Section 5
APPLICATION NOTES
In applications where the input is sinusoidal and of small
proportional frequency deviation, a relatively stable load
may be resonantly tuned to present a real value of im-
pedance to the amplifier.
Any load, no matter how complex its behavior, has a
V-l operating range which may be mapped by the follow-
ing test.
The maximum voltage and amperage excursions in all
directions about zero (center of scope screen) define
the volt-ampere operating range of the load. If a load is
known to be linear over its operating range it is not nec-
essary to supply the maximum desired power to the load.
The test may be conducted at low signal levels and the
current-sensing resistor (indicated as 0.1 ohm) may be
enlarged to a convenient value for the oscilloscope’s de-
flection sensitivity. The resulting plot may be then linearly
scaled to the desired operating level.
LOAD
under
Note:
Scope and amplifier grounds are not common.
Vertical input reads amperes vertically. If scope
has an inverter, invert to read (+) A.
AMPLIFIER LIMITS OF VI OUTPUT
Vout
L I M I T
LINE BLOWS
SINGLE S L O W S
X
S H O R T C I R C U I T C O N T I N U O U S L I M I T
AT DC IF BOTH A
R
EA OVER LIMITER (AC)
CHANNELS ARE DRIVEN
“ARIES (SIGNAL DEPENDENT)
- M A X A C L I M I T V O U T A T
M A X . )
MAX. CONT. AC POWER
- - - -
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