ICL8038_01 Datasheet, PDF (7/12 Pages) Intersil Corporation – Precision Waveform Generator/Voltage Controlled Oscillator

ICL8038
SWEEP
R_A
VOLTAGE
4
R_B
5
69
V+
R_L
8
ICL8038
3
10
11
12 ²
C
81K
V- OR GND
FIGURE 5B. CONNECTIONS FOR FREQUENCY SWEEP
FIGURE 5.
Typical Applications
The sine wave output has a relatively high output impedance
(1kΩ Typ). The circuit of Figure 6 provides buffering, gain
and amplitude adjustment. A simple op amp follower could
also be used.
R_A
74
R_B
5
8
ICL8038
6
AMPLITUDE
2
+
100K ₇₄₁
-
V+
20K
10
11
4.7K
C
V-
FIGURE 6. SINE WAVE OUTPUT BUFFER AMPLIFIERS
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.
R_A
R_B
74
5
9
V+
15K
8
ICL8038
1N914
11
10 ²
C
2N4392
-15V
1N914
STROBE
100K
OFF
ON
+15V (+10V)
-15V (-10V)
FIGURE 7. STROBE TONE BURST GENERATOR
To obtain a 1000:1 Sweep Range on the ICL8038 the
voltage across external resistors R_A and R_B must decrease
to nearly zero. This requires that the highest voltage on
control Pin 8 exceed the voltage at the top of R_A and R_B by a
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.
0.1µF
1N457
DUTY CYCLE
1K
4.7K
4.7K
+10V
15K
10K
FREQ.
5
4
69
8
ICL8038
3
10
11
12 ²
20K ≈15M
0.0047µF
DISTORTION
100K
-10V
FIGURE 8. VARIABLE AUDIO OSCILLATOR, 20Hz TO 20kHzY
7