Tektronix FG 5010 User Manual

Theory of Operation - FG 5010
DATA
FREQ
CONTROL
VOLTAGE
DATA
4-10
SYM
GAIN
10
BIT
10
BIT
UP
SYM
DAC
ON
SYM
DAC
V
UP
UP SYMMETRY
DAC
DOWN SYMMETRY
OAC
VON
tracking
between this
circuit and the
Down
Symmetry
DAC
.
Current
through the
digitally
-
selected
ladder
resistors is
ap
plied to the
inverting
input of
U1521 .
Feedback for the circuit
is provided by way of R1521 and the resistance internal to
U1511 .
The
resulting
output of
the
stage is a
dc
voltage
that
is a
digitally -
selected
fraction of
the
applied
frequency con
trol
voltage
.
Up
Sym
Ofst
adjustment
R1537 is
initially
adjusted for
zero
voltage at pin 3.
Up Cur
Ofst
adjustment is set for
zero
voltage at pin 6 of
U1521 with a
zero
word
applied
to
the
programmable DAC .
Finally ,
R1537
is
adjusted for zero col
lector
current from
Q1433
.
Up
Ramp
Current Source
UP
This
circuit
converts the V
voltage
from the Up
Sym
metry
DAC to the
current
that
charges the
Loop
Capacitor
stage
when
the
triangle
wave
is
rising
positive
.
The
circuit
consists of
amplifier
U1421 ,
transistor
Q1433
, and
related
components . The
circuit
is an
operational
amplifier that uses
R1438 as
the
principal
feedback element .
Any
change in
voltage
applied
to
R1532 , the input
resistance
, is
inverted
at
the
output of
U1421 and
causes a
change
in
current
through
Q1433
.
The
output
from
the
collector of
Q1433 is a
current
that
is
fed to
the
Transistor
Bridge
circuit
to be
switched in
or out
of the
Loop
Capacitor
charge
path
.
Up
Current
Null
+
V
IUP
TRANSISTOR
BRIDGE
-V
UP RAMP
CURRENT
SOURCE
Fig . 4-4 .
Symmetry
circuits
simplified
diagram .
DOWN RAMP
CURRENT
SOURCE
ION
TO SHRINK
SECTION AND
PHASE
CLAMP
TO
LOOP CAP
TO
SHRINK
SECTION
3467-11
Adj
potentiometer R1531 is
adjusted
to
make up for
minor
differences
in
tracking
between
the divider
that
consists of
R1541 ,
R1536 , and
R1433 , and the
resistors
that
are in the
feedback
path
.
Down
Symmetry
DAC
The
Down
Symmetry DAC
produces
the
V
voltage
that
is applied to the Down Ramp Current Source and the Shrink
Control
Amplifier . The
circuit
consists of a 10
bit pro
grammable DAC ( U1611 ) , amplifier U1622 , and related
components .
Except for the symmetry gain adjustment and the circuit
to which it is
connected
,
the Down
Symmetry
DAC
is identi
cal to the
Up
Symmetry DAC
.
Refer
to
that
description for
more
details
.
Down Ramp Current Source
DN
This
circuit converts the V
voltage
from the
Down
Symmetry
DAC
to the current
that charges the
Loop Ca
pacitor when the
triangle wave is
falling
negative
.
The circuit
consists
of
amplifier
U1551 ,
transistor Q1443 , and related
components
.
C
U
C
U
U
D
)
U
U
U
U

Tektronix FG 5010 Specifications

General

Brand	Tektronix
Model	FG 5010
Category	Portable Generator
Language	English