Theory Of Operation; General - HP 202A Operating And Service Manual

Sect. 1 1 1 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 a t 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"
o r 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
a r e 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 a t point B and the average
level a t 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
@
=
O U T P U T
A M P L I F I E R
C R I l
AVE
F t f H
vOLT4GE FROM
@ T O
@
CR13
VOLTAGE FROM
+
SWITCHING SIGNAL
+
- S W I T C H I N G R E F
,
, ,