6

constant to insure constant reverse voltage bias on the

photo diode.

Low-Frequency Multivibrator

In this application, one half of the CA3290 is used as a

conventional multivibrator circuit. Because of the extremely

high input impedance of this device, large values of timing

small leakage timing capacitors. The second half of the

CA3290 is used as an output buffer to insure that the

multivibrator frequency will not be affected by output loading.

connected between +15V and GND.

Window Comparator

Both halves of the CA3290 can be used in a high input

impedance window comparator as shown in Figure 7. The

LED will be turned “on” whenever the input signal is above

+

-

+15V

7

6

5

+15V

3.3k

Ω

60M

Ω

1.0

µF

10k

Ω

140k

Ω

+

-

1

+15V

1N914

8

4

0.01

µF

1N914

+15V

3

2

1M

Ω

+15V

15k

Ω

1.5M

Ω

2M

Ω

15

k

Ω

C30809

X 60s TIME

FIGURE 5. LIGHT CONTROLLED ONE-SHOT TIMER

+

-

+15V

CA3290

7

6

5

3.3k

Ω

1M

Ω

+

-

CA3290

1

8

4

+15V

2

3

15k

Ω

1M

Ω

+15V

20M

Ω

1M

Ω

1M

Ω

+15V

0.36

µF

1M

Ω

tPeriod

10s

==

t2R

e

2R

P

R

2

------------ 1

+







=

C

FIGURE 6. LOW FREQUENCY MULTIVIBRATOR

+

-

CA3290

+

-

1

7

8

4

670

Ω

3.9k

Ω

LED

2N2102

2

3

6

5

100k

Ω

100k

Ω

+15V

+15V

INPUT

47k

Ω

47k

Ω

6.8k

Ω

FIGURE 7. WINDOW COMPARATOR

CA3290, CA3290A