icl8038 Intersil Corporation, icl8038 Datasheet - Page 7

• Manufacturer Part Number: icl8038
• Description: Precision Waveform Generator/voltage Controlled Oscillator
• Manufacturer: Intersil Corporation

Typical Applications
The sine wave output has a relatively high output impedance
(1k Typ). The circuit of Figure 6 provides buffering, gain
and amplitude adjustment. A simple op amp follower could
also be used.
FIGURE 5A. CONNECTIONS FOR FREQUENCY MODULATION
FIGURE 5B. CONNECTIONS FOR FREQUENCY SWEEP
VOLTAGE
FIGURE 6. SINE WAVE OUTPUT BUFFER AMPLIFIERS
SWEEP
FM
7
8
10
R
4
R
C
7
8
A
8
10
4
10
4
ICL8038
R
C
A
R
C
5
A
R
ICL8038
B
ICL8038
11
5
11
5
FIGURE 5.
R
B
R
11
6
B
7
2
12
6
AMPLITUDE
12
6
81K
9
3
2
81K
100K
9
3
2
R
4.7K
L
R
+
-
741
L
V+
V- OR GND
V+
V- OR GND
20K
V+
V-
ICL8038
With a dual supply voltage the external capacitor on Pin 10 can
be shorted to ground to halt the ICL8038 oscillation. Figure 7
shows a FET switch, diode ANDed with an input strobe signal
to allow the output to always start on the same slope.
To obtain a 1000:1 Sweep Range on the ICL8038 the
voltage across external resistors R
to nearly zero. This requires that the highest voltage on
control Pin 8 exceed the voltage at the top of R
few hundred mV. The Circuit of Figure 8 achieves this by
using a diode to lower the effective supply voltage on the
ICL8038. The large resistor on pin 5 helps reduce duty cycle
variations with sweep.
The linearity of input sweep voltage versus output frequency
can be significantly improved by using an op amp as shown
in Figure 10.
FIGURE 8. VARIABLE AUDIO OSCILLATOR, 20Hz TO 20kHzY
FREQ.
20K
10K
7
8
11
FIGURE 7. STROBE TONE BURST GENERATOR
4
R
A
15M
0.1 F
ICL8038
5
8
R
B
10
5
4.7K
0.0047 F
C
1K
10
DUTY CYCLE
1N457
ICL8038
-15V
9
2
2N4392
11
4
4.7K
A
1N914
and R
100K
12
6
B
OFF
1N914
15K
DISTORTION
100K
must decrease
ON
9
3
2
A
and R
+15V (+10V)
-15V (-10V)
STROBE
15K
B
+10V
-10V
by a
V+