Philips PM 5715 - Page 6

4. Block
diagram
description
Note: Figures
in brackets
refer
to waveforms
shown in
Fig.
4—
1
.
Astable multivibrator
The astable multivibrator
generates square
wave pulses from which
all internal pulses
are
derived.
Switch
REPETITION
TIME, SKI,
and its
vernier,
R1, enable
adjustment of the
repetition time
between
Is and 20ns. The
multivibrator is
inoperative when switch
REPETITION
TIME is
set to
position
EXT.
Trigger circuit
In
the
EXT. mode the
pulse
generator
can
be
triggered by an external
signal applied at
con-
nector
TRIGG./GATE IN,
BUI.
The triggering
signal is fed
to
a
Schmitt trigger,
producing
an
appropriate
signal
for the
remaining circuits of the
generator.
With no
triggering
signal applied, a
single
pulse
is generated by the
Schmitt
trigger when push-
button switch
SINGLE SHOT,
SK5,
is
depressed.
With switch
REPETITION TIME set
to
one
of the
time positions,
the astable
multivibrator can
be
gated by a
signal applied at
input
TRIGG./GATE
IN. Bursts of pulses
which are
synchronized
with the
gating
signal are
then obtained.
Gate,
sync,
amplifier and
first pulse
shaper
The output
of the gate
is
available at front
panel
connector
SYNC. OUT,
BU2. The
repetition
frequency
and the duty
cycle of
this signal
is
determined
by the
astable
multivibrator,
or, at
external
operation, by
the
triggering
signal.
The
pulse
shaper is controlled
by the
leading
edge
of the
input signal
(1)
from
the gate. The
shaper
provides a needle
pulse
(2)
which
is
controlling
the delay
circuit.
Delay
circuit, second
pulse
shaper and
duration
circuit
The delay
circuit
delivers
pulses
(3)
whose
width is
adjusted
with the
DELAY control,
SK2,
and its
vernier,
R2. The
trailing
edge of
these
pulses
controls the
next pulse
shaper
which
feeds a
needle pulse
(4)
to
the
duration
circuit.
Similar to
the
delay circuit,
the
duration
circuit
produces
pulses whose
width is
set with
the
DURATION controls,
SK3, and
its
vernier, R3.
In the
DOUBLE
mode, a
needle pulse
(5)
derived
from
the
leading
edge of the delay
pulse is
gated
to
the
input of the duration
circuit.
Double pulses
are then
generated. The output of
the duration
circuit is
available
at
front panel
connector
AUX. OUT,
BU3.
This signal
having a
fixed amplitude
occurs ap-
proximately
12ns
ahead of the main
signal at
front
panel connector
PULSE
OUT,
BU4.
Normal
or inverted
mode of the
signal at
PULSE
OUT can be
selected with
switch
NOR-
MAL/INV.,SK10.
Switch T/2,
SK8
When
the
T/2
switch,
SK8,
is
depressed, the
delay
and duration
circuits
are separated
from
the
output stage.
The signal
(1)
produced by
the
internal multivibrator,
or the
Schmitt
trigger,
is fed directly to
the
output stage.
However, the
AUX. OUT
connector
still
provides the
signal with
adjustable delay
and
duration.
In
the
EXT. position
of switch
REPETITION
TIME
and with
switch T/2
depressed, the
triggering
signal applied at
input
TRIGG./GATE
IN
is
fed
only
through the
output stage
and is
available
at
connector
PULSE OUT
with the
same
repetition time and
duty
cycle as the
original
signal, but
with
a
rise
time, shape,
and
am-
plitude
in conformance
with the
specification of
the
PM
5715.
Ramp
generator and
output circuit
From switch T/2 the
pulses
are fed via the
dif-
ferential
amplifier
to
the
ramp
generator which
determinies the
transition time
of the pulses.
The rise and
fall times are
independently
and
continuously
set with
controls
RISE, R4 and
FALL, R5.
An emitter
follower
provides
a
low
impedance
output to
the
dual-channel output
stage.
The
polarity switch
"h
—
"
diverts the
signal
into
the positive
or negative
channel.
In
both
channels, the
amplitude
can be con-
tinuously
controlled with the
AMPLITUDE ver-
nier R7.
Next, a
resistive
network
provides attenuation
of the signal as set
with push-button
switches
AMPLITUDE, SK1 1...
SKI
4.
The signal is then
fed
to
the output
connector,
PULSE
OUT,
BU4.
A d.c.-offset circuit
supplies a
positive or
negative current to
the output
line so that
baseline
shift
can
be
introduced by
means of
control
DC-OFFSET, R6.