EasyManua.ls Logo

Philips PM 5167 - Sine Shaper-Unit U4

Philips PM 5167
77 pages
Go to English
Save Page as PDF
Print Icon
To Next Page IconTo Next Page
To Next Page IconTo Next Page
To Previous Page IconTo Previous Page
To Previous Page IconTo Previous Page
Loading...
43
By
setting
switch
SINGLE
SHOT
MODE
from
SET
PHASE
to
START,
a trigger pulse
appears
at
U5/513
to
set
the
fl
i
p-
flop.
Diode U5/
419
avoids
multiple
triggering as a
re
s
ult
of
bouncing
contacts
of
switch
START.
The
flip-flop
can
also be
set
by a negative
voltage
jump
of
5 V
at
the
CONTROL
INPUT
(connection
U5/ X = O V) . Due
to
this
a voltage
is
available
at
connect
i
on
X
and
the
oscillator
is
start.
However,
the
first
positive-going
square-wave
resets
the
flip-flop again, so
that
oscillation
stops
af
ter
one
cycle
.
Potentiometer
SET
PHASE
is
adjusted
by
means
of
potentiometers
U5/679,
682.
U5/682
serves
to
adjust
the
positive
part
and
U5/679
the
negative
part
of
the
square-wave
.
Both
adjusting
operations
are
interdependent.
3.1.4_
Sine-shaper
Unit
U4
The
sine-shaper
consists
of
:
- a
diode-resistor
network
- a
circuit
for
peak
compensation
- a
delay
section
to
start
peak
compensation
at
the
right
time
- an
inverting
wide-band
amplifier
3.1.4.1.
The
diode-resistor
network
fig.
22
converts
a
triangular
signal
of
lOV
pp
into
a sine-wave signal
with
an
ampli
tude
of
5V . 2/rr =
3,18
V.
Each
diode
(U4/401
to
414)
is
biased by a
different
voltage
from
one
voltage divider each
(U4/601,
604
to
619
and
603,
606
to
621)
.
They
function
as
amplitude-dependent
switches
and
are increasingly
connecting
in
paralIei
with
resistors
U4/
605, 608,
611
,
614,
617
and
620
at
rising
triangular
voltage.
Magnitude
and
symmetry
of
the
d i
ode
bias
is
determined
by
two
voltage
sources
U4/351
and
313
to
315,
which
are
coupled
to
better
the
temperature
compensation.
Adjustment
is
performed
by
means
of
U4/666,
669
.
The
diodes
with
the
highest
bias
voltage
U4/413
and
414
serve
to
form
the
sine-wave
tops
.
They
shou
Id
form,
together
with
the
corresponding
voltage
source,
an
extremely
low-ohmic
current
path.
As this
only
can
be
approximated
due
to
the
forward
resistance
of
the
diodes
,
the
peaks
obtained
are
cut-off
by
a
compensating
ci
rcuit
.
3.1.4
.2.
The
peak-compensating
circu
it
consists
of
transistors
U4/301,
302,
303
and
305.
Diodes
U4/413,
414
are
biased
by
U4/301,
302
in
such
away,
that
they
only
conduct
during
the
period
the
tops
of
the
sine-wave are
formed.
The
peak
compensation
takes
over
the
current
by
means
of
transistors
U4/301
and
302
respectively
via
diodes
U4/413
and
414
.
Stages
U4/
303
and
305
respectively
ampl
if
y
and
invert
the
current,
which
is
then
supplied
to
the
summing
point
at
resistor
640
.
3.1.4
.
3.
The
delay
circuit
in signal
path
U4/504
to
506;
636,751,752
compensates
the
phase
delay
of
the
peak
compensation
at
frequencies
higher
than
1 MHz.
Due
to
its low-pass
characteristic
this
delay
circuit
causes
the
distortion
facto
r
to
be
decreased
for
frequencies
higher
than
1 M
Hz
.
3.
1.4.4.
I n
wide-band
ampl
ifier
U4/307
to
312
the
voltage loss
of
2/rr
caused
by
the
sine-
shaper
is
compensated
by
amplifying
V = - rr/2.
Consequently
the
sinewave signal
at
the
output
has
the
same
peak
value as
the
triangular
input
voltage.
The
DC-offset
of
the
output
voltage
is
adjusted
by
U4/644,
while
the
frequency
response
for
range 1
to
10
MHz
is
adjusted
by
U4/508.
3.1.5.
Power amplifier Unit
U6
The
power
ampl ifier fig.
22
is
complementary
and
symmetrically
arranged
and
contains:
- an
emitter-follower
stage
- a
voltage-amplifying
cascode
part
- a
driver
stage
-
an
A/B
-
power
output
stage
U6/309,
310
-
elements
for
a
DC
OFFSET-control
- an
OVERRANGE
indicator
-

Table of Contents

Related product manuals