Sect.
111
Page
1
SECTION
Ill
3-1
GENERAL
Figure 3-1 depicts the general scheme of the @Model
202A
and indicates the waveforms produced. The bi-
stable circuit consists of a flip-flop circuit capable
of producing a square-wave output at point
A,
pro-
vided
it
is
triggered at the proper time. This
is
done by including in the bi-stable circuit, a two-way
comparator circuit which produces the proper trig-
gers for the flip-flop whenever the switching signal
becomes equal to either the
"plus switching reference"
or the "minus switching reference". The triangular
switching signal returned to the bi-stable circuit
THEORY OF OPERATION
is
that seen between points
B
and
D.
The conversion
of square wave to triangular wave takes place in
the integrator unit which
is
carefully designed to
produce an accurate integral of the applied square
wave. The bi-stable circuit and linear integrator
are loop coupled in such a manner that the resulting
relaxation oscillator
is
suitable for very low fre-
quency operation.
The
sinewave output
is
taken from a point
C
between
the triangular voltage at point
B
and the average
level at point
D.
The resistance between
B
and
C
is
fixed, and the network between
C
and
D
is
a
1
OUTPUT
Figure 3-1. Model
202A
Function Generator
-
+
SWITCHING REF
0
-
8+
CR12
-
CRlO
@
=
OUTPUT
AMPLIFIER
CRIl
AVE
FtfH
vOLT4GE FROM
@TO
@
CR13
VOLTAGE FROM
+
SWITCHING SIGNAL
+
-SWITCHING REF
,
, ,
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