8-159

Typical Applications

The sine wave output has a relatively high output impedance

(1k

Ω Typ). The circuit of Figure 6 provides buffering, gain

and amplitude adjustment. A simple op amp follower could

also be used.

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 volt-

nearly zero. This requires that the highest voltage on control

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 9.

C

ICL8038

456

2

11

10

8

7

100K

V-

V+

AMPLITUDE

20K

+

-

741

4.7K

FIGURE 6. SINE WAVE OUTPUT BUFFER AMPLIFIERS

C

ICL8038

45

9

10

11

8

7

1N914

-15V

V+

STROBE

2

2N4392

1N914

15K

100K

OFF

ON

+15V (+10V)

-15V (-10V)

FIGURE 7. STROBE TONE BURST GENERATOR

0.0047

µF

DISTORTION

ICL8038

546

9

2

12

11

10

8

4.7K

-10V

3

+10V

20K

4.7K

1K

DUTY CYCLE

15K

1N457

0.1

µF

100K

10K

FREQ.

IGURE 8. VARIABLE AUDIO OSCILLATOR, 20Hz TO 20kHzY

ICL8038