INSTRUCTION
MANUAL
-
MODEL
DLP
400-5-750A
22
input
of
U1
.
This
increased
voltage
requires
approximately
5A
of
current
to
flow through
the
shunt, SH101,
before
there
is
a sufficient
voltage
drop
to
cause
U1
to
regulate
the
current through
the
pass
structure.
5.6
VOLTS
In
the
volts
mode,
the
Dynaload
is
converted
into
a
constant
voltage
regulator
at
the
input
terminals similar
to
a
shunt
regulator or a zener
diode.
The
input
voltage
is
applied
through
R23
and
R20
and
the
volts
adjust
to
the
non-inverting
input
of
U1
,
and a
constant
voltage
reference
is applied
from
resistive
divider
R17
and
R18
to
the
inverting
input of
U1
,
replacing
the current
feedback
loop.
Accordingly,
if
the input
voltage
tends
to
exceed
the
voltage
selected
by
the
volts
control on
the
front
panel,
U1
condutcs
more, thereby
turning
on
Q118
and
the
pass
structure,
causing
the
Dynaload
to
draw
additional current,
attempting
to maintain constant
voltage
at
the
input.
5.7
EXTERNAL
MODULATION
MODE
The
external modulation mode
provides
for
the
use
of
an
external reference
applied
to
the
external
modulation
input
in
place
of
zener
diode
VR8
.
The coarse
and
fine
DC
load
adjusts
on
the
front
panel
can
then
be
used
to
define
the
programming
sensitivity
of the external
modulation
signal.
If
a pulse
load
is
desired,
a
pulsing
signal
may
also be
applied
to
the
external
modulation
input.
[HP400-5-75QA]
