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Tektronix FG 5010 User Manual

Tektronix FG 5010
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7
c
П
П
1
ņ
П
П
(
The
Sine
Shaper
operates
as
follows
:
The
LF
or
HF
trian
gle
from
the
Function
Selector
relay
is
applied
to
the
input
network
that
consists
of
R1030
,
CR1031
,
CR1030
,
CR1032
,
CR1033
,
and
R1031
;
and
the
input
termination
that
consists
of
R1020
,
R1022
and
R1021
.
Because
of
the
non
-
linear
impedance
characteristics
of
the
diode
bridges
,
the
load
on
the
Triangle
Buffer
will
vary
significantly
with
output
voltage
.
The
purpose
of
the
resistor
-
diode
network
across
the
input
is
to
reduce
the
input
impedance
fluctu
ations
that
might
otherwise
affect
the
triangle
linearity
.
Input
resistors
R1020
and
R1021
also
help
stabilize
the
input
im
pedance
.
SINE
DRIVE
adjustment
R1022
sets
the
ampli
tude
of
the
incoming
drive
signal
.
Thermistor
RT1020
,
in
conjunction
with
parallel
resistor
R1032
,
increases
the
drive
to
the
bridges
to
compensate
for
increases
in
operating
temperature
.
If
zero
voltage
is
applied
to
the
inputs
of
the
diode
bridges
,
all
bridge
diodes
conduct
.
Since
the
diodes
are
matched
,
only
small
variations
in
voltage
drop
exist
across
one
diode
or
another
in
a
particular
bridge
,
and
approxi
mately
equal
current
flows
through
each
diode
in
a
particular
bridge
.
The
actual
current
level
is
controlled
by
the
resistors
to
the
+12
and
12
V
supplies
.
Since
the
bridges
are
balanced
when
zero
volt
is
applied
,
the
output
is
also
zero
volt
at
that
time
.
If
the
input
voltage
rises
positive
,
the
output
voltage
will
follow
,
due
to
the
cur
rent
-
steering
that
occurs
in
each
bridge
.
Using
the
bridge
composed
of
CR1120
,
CR1121
,
CR1122
,
and
CR1123
as
an
example
,
applying
a
positive
input
voltage
reduces
the
current
through
CR1120
,
causing
the
voltage
at
the
junction
of
CR1120
and
CR1122
to
become
more
positive
.
At
the
same
time
,
the
positive
input
voltage
increases
the
current
through
CR1121
,
causing
the
voltage
at
the
junction
of
CR1121
and
CR1123
to
move
positive
.
These
changes
cause
more
current
to
flow
through
CR1122
and
less
through
CR1123
,
disturbing
the
balanced
condition
that
ex
isted
when
no
signal
was
applied
.
The
excess
current
through
CR1122
flows
through
R1221
and
R1242
,
provid
ing
a
positive
input
voltage
to
the
Sine
Buffer
.
As
current
flow
through
the
diodes
becomes
unbalanced
,
the
voltage
drops
across
the
diodes
change
nonlinearly
,
in
accordance
with
diode
characteristics
.
More
positive
input
causes
the
current
through
CR1120
to
decrease
,
in
turn
de
creasing
the
voltage
drop
,
while
the
current
through
CR1122
increases
,
which
increases
the
voltage
drop
across
that
diode
.
The
result
of
the
two
changes
is
that
the
output
of
the
bridge
rises
more
slowly
than
the
input
,
following
a
curve
determined
by
the
source
and
load
impedances
,
the
supply
voltages
,
the
initial
diode
current
,
and
the
diode
cur
rent
-
voltage
characteristics
.
As
the
input
voltage
continues
to
move
positive
,
the
cur
rent
through
CR1120
and
CR1123
is
eventually
reduced
to
Theory
of
Operation
-
FG
5010
zero
.
When
this
occurs
,
all
the
current
from
the
+12
V
sup
ply
flows
through
R1123
,
CR1122
,
and
R1221
to
develop
a
voltage
across
R1242
,
the
input
to
the
Sine
Buffer
.
Beyond
this
point
,
further
increases
in
the
Sine
Shaper
input
voltage
have
no
effect
on
the
output
because
CR1120
and
CR1123
become
reverse
-
biased
,
preventing
the
input
from
affecting
the
output
.
Similarly
,
when
the
input
voltage
moves
negative
,
current
through
CR1120
and
CR1123
increases
as
current
through
CR1121
and
CR1122
decreases
.
As
the
input
becomes
more
negative
,
current
through
CR1121
and
CR1122
be
comes
zero
.
After
this
point
is
reached
,
the
input
has
no
effect
on
the
output
.
The
breakpoint
for
each
of
the
bridges
(
where
two
of
the
four
diodes
becomes
reverse
-
biased
)
depends
upon
the
ini
tial
diode
current
,
which
is
established
by
the
resistors
to
the
+12
and
12
V
supplies
.
The
highest
-
value
resistors
establish
the
lowest
currents
,
causing
that
bridge
to
reach
its
breakpoint
first
.
The
result
of
the
combination
of
four
bridges
is
an
incremental
approximation
to
a
sine
wave
in
linear
segments
,
with
the
transitions
from
one
segment
to
another
smoothed
by
the
nonlinear
characteristics
of
the
diodes
.
Although
all
sixteen
diodes
in
the
Sine
Shaper
are
matched
,
some
small
differences
may
exist
that
would
cause
an
offset
in
the
output
of
the
stage
.
Sine
Input
Offset
adjustment
R1033
is
set
to
compensate
for
such
differ
ences
,
and
to
compensate
for
any
offset
that
might
occur
from
the
Triangle
Buffer
Circuit
.
Sine
Buffer
The
Sine
Buffer
stage
receives
the
sinewave
output
from
the
Sine
Shaper
,
amplifies
it
,
and
applies
the
signal
to
the
function
selector
.
The
buffer
consists
of
transistors
Q1230A
,
B
,
C
,
and
D
,
Q1320
,
Q1321
,
Q1340A
and
B
,
plus
related
components
.
The
sinewave
from
the
Sine
Shaper
is
applied
to
the
base
of
Q1230A
,
part
of
a
differential
pair
with
Q1230B
.
These
two
transistors
are
part
of
a
five
-
transistor
package
on
a
single
substrate
;
Q1230A
and
Q1230B
are
the
most
closely
matched
pair
of
the
five
.
Gain
for
the
stage
is
set
by
the
Sine
Amplitude
adjustment
,
R1233
.
Current
through
each
leg
of
the
differential
pair
is
varied
by
R1239
,
the
Sine
Offset
adjustment
,
which
compensates
for
any
output
offset
requirements
.
The
tap
between
R1247
and
R1243
is
to
set
the
voltage
to
the
substrate
at
approximately
-5
V
,
to
avoid
exceeding
the
maximum
voltage
of
the
Q1230
package
.
4-29

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Tektronix FG 5010 Specifications

General IconGeneral
BrandTektronix
ModelFG 5010
CategoryPortable Generator
LanguageEnglish

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