ca3240a Intersil Corporation, ca3240a Datasheet - Page 11

• Manufacturer Part Number: ca3240a
• Description: Dual, 4.5mhz, Bimos Operational Amplifier With Mosfet Input/bipolar Output
• Manufacturer: Intersil Corporation

Differential Light Detector
In the circuit shown in Figure 11, the CA3240E converts the
current from two photo diodes to voltage, and applies 1V of
reverse bias to the diodes. The voltages from the CA3240E
outputs are subtracted in the second stage (CA3140) so that
only the difference is amplified. In this manner, the circuit
can be used over a wide range of ambient light conditions
without circuit component adjustment. Also, when used with
a light source, the circuit will not be sensitive to changes in
light level as the source ages.
C30809
PHOTO
DIODE
C30809
PHOTO
DIODE
11
+15V
5.1K
1.3
13K
K
FIGURE 11. DIFFERENTIAL LIGHT DETECTOR
2
3
5
6
+15V
-15V
1/2
CA3240E
1/2
CA3240E
+
+
-
-
0.015µF
0.015µF
CA3240, CA3240A
100K
100K
8
4
1
7
200K
2K
2K
3
2
CA3140
+
-
-15V
200k
7
4
+15V
6
OUTPUT
March 4, 2005
FN1050.6