Elenco Surface Mount Generator Kit - Manual (Page 13)

-12-
FUNCTIONAL DESCRIPTION
The FG-600 is a function generator integrated circuit capable of producing high quality sine, triangle, and
square waves of high stability and accuracy. A picture of each waveform is shown below:
THEORY OF OPERATION
The heart of the FG-600 Function Generator is the
XR-2206 monolithic function generator integrated
circuit. The XR-2206 is comprised of four main
functional blocks as shown in the functional block
diagram (Figure 1). They are:
● A Voltage Controlled Oscillator (VCO)
● An Analog Multiplier and Sine-shaper
● Unity Gain Buffer Amplifier
● A set of current switches
The VCO actually produces an output frequency
proportional to an input current, which is produced by
a resistor from the timing terminals to ground. The
current switches route one of the currents to the VCO
to produce an output frequency. Which timing pin
current is used, is controlled by the FSK input (pin 9).
In the FG-600, the FSK input is left open, thus only
the resistor on pin 7 is used. The frequency is
determined by this formula:
f
o
= 1/RC Hz
where f
o
is the frequency in Hertz
R is the resistance at pin 7 in Ohms
C is the capacitance across pin 5 and 6 in Farads
Sine Wave Triangle Wave Square Wave
FUNCTIONAL BLOCK DIAGRAM
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
Figure 1
Current
Switches
VCO
Multiplier
and
Sine
Shaper
+1
AM Input
Sine/Saw
Output
Mult. Out
V+
Timing
Capacitor
Timing
Resistor
Symmetry
Adjust
Waveform
Adjust
Ground
Sync
Output
Bypass
FKS
Input
Note that frequency is inversely proportional to the
value of RC. That is, the higher the value of RC, the
smaller the frequency.
The resistance between pins 13 and 14 determine the
shape of the output wave on pin 2. No resistor
produces a triangle wave. A 200Ω resistor produces a
sine wave.