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b.
Pstching
A
sirnpl~£ied
diagram and a typical patching scheme for the Dual
Log
X DFG and the
Dual 1/2 Log X DFG are shown in Figure 15.
The Dual Log X DFG is shown in the
figure
~ut
the information is applicable to both units except for the labeling of
the output variable.
The DFG terminated on the upper portion of the patching module
accepts
a
negative voltage, -X, and produces a positive voltage of 5 10glO IIOXI
from the associated amplifier.
The lower DFG accepts a positive voltage, Y, and
produces a negative voltage of -5 10glO lOY from its associated amplifier.
Each
amplifier has a 5000 ohm feedback
res~stor.
The input voltage magnitude should not
be less than 0.1 volts in order to maintain accuracy and/or avoid overloads.
Care
should be taken not to apply an input voltage of the wrong polarity; doing so will
not damage the DFG but it does constitute a severe overload on the amplifiers in the
circuit.
-IN
O
So
00
R21
5K
0
0
+INO
+
lOG X
DFG
So
0
0
R24
5K
LOGX OF
16.126
o.
SIMPLIFIED DIAGRAM
OF UNIT
X
Y
-IN
S
0
0
0
+IN
S
0
OG X DFG
16.126
-IN
X
~
...... -
+5 lOG
10
lOX
")0.. ............
-5l0G
10
10Y
b.
TY
P
ICAl PATCH I NG
C.
SYMBOLS
Figure
15.
Patching the Log
X
JJFG's
9.
VARIABLE DIODE FUNCTION GENERATOR GROUPS 2.645
AND
2.713
a.
General Description
-5l0G
10
10X
The variable diode function generators (VDFG's) are used in conjunction with dc
amplifiers to produce a segmented straight-line approximation to an arbitrary
function.
They accept an input voltage X and produce an output voltage Y
=
f(X),
where f is a predetermined, single-valued function that can be non-monotonic.
The
desired function is produced by summing the outputs from biased diode networks.
As the input voltage changes, the diodes effectively switch the input resistors of
a summing amplifier, thus varying the amplifier gain.
The output voltage of the
amplifier changes in accordance with the input voltage by a sequence of straight-
line segments.
Two basic VDFG groups are available.
The 2.645 Groups provide plus and minus units
with variable slopes and breakpoints; the 2.713 Groups have variable slopes and
fixed breakpoints.
The groups are listed below.
32
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