OPERATING
INSTRUCTIONS
This section
will
familiarize you
with
the
capabilities
and
operation
of
the
7A42. A
thorough
understanding of
this
information
will
remove
later
uncertainty
when
operating
your 7A42.
OPERATION
For
operation,
your
7A42
Logic
Triggered
Vertical
Amplifier
must be
properly
installed
in
a
Tektronix
7000-series
mainframe.
Installation
is
explained
in
the
General
Information section of
this
manual.
SIMPLIFIED BLOCK DIAGRAM
OF
THE 7A42
The
7A42
has
six
basic
functional
blocks
of
circuitry: Attenuators,
Amplifiers,
Channel
Switching, Trigger
Threshold
Generators,
Trigger
Comparators
and
Trigger
Logic
(see
Fig.
2-1).
Each
channel
(CH1
through CH4)
has its
own
Attenuator,
Amplifier,
Trigger
Threshold
Generator,
and
Trigger
Comparator.
Impedance
matching
(50Ω/1MΩ)
and
gain
switching
(VOLTS/DIV)
are
accomplished
by
the
Attenuator.
There
are
two
signal outputs
from
each Attenuator,
one
signal
is
applied to
the
Trigger
Comparator
and
the
other
to the
Amplifier,
for
each
channel.
The
Amplifiers
provide
the
signal
gain
necessary
to
drive
the
vertical
amplifiers
within
the
host
oscilloscope mainframe.
The
Channel
Switching
stage
provides
vertical
signal
processing
to
display
the
channel
traces
and
the
Trigger
View
trace
on
the
mainframe
crt.
This
is
accomplished
by
either
chopping
between
the
channels
selected
for
display
or
by
displaying
them
alternately
after
each
sweep
of
the
time
base.
The
Trigger
Comparator
compares
the
signal from the
Attenuator
with
the
voltage
of
the
Trigger
Threshold
Generator.
When
the
signal
from
the
Attenuator exceeds
the
Threshold
Voltage,
the
Trigger
Comparator
produces
an
output
which
is
applied
to
the
Trigger
Logic
stage.
The
Trigger
Logic
stage
accepts
logic
levels
from
the
Comparator
and
compares
them
with
the
programmed
logic
level,
of
each
channel.
When
the
applied
input
signal(s)
conform
to
the
programmed
trigger
logic
conditions,
a
trigger pulse
is
produced.
The
Trigger
Logic
conditions
are
user programmed
from
the
front
panel.
2-1