Datasheet

REV.
ADG781/ADG782/ADG783
–6–
FREQUENCY – Hz
–30
OFF ISOLATION – dB
–40
–110
–120
–130
10k 100k 1M 10M 100M
–100
–90
–80
–70
–60
–50
V
DD
= 5V, 3V
TPC 5. Off Isolation vs. Frequency
FREQUENCY – Hz
–30
CROSSTALK – dB
–40
–110
–120
–130
10k 100k 1M 10M
V
DD
= 5V, 3V
100M
–100
–90
–80
–70
–60
–50
TPC 6. Crosstalk vs. Frequency
FREQUENCY – Hz
0
ON RESPONSE – dB
–6
10k 100k 1M 10M
V
DD
= 5V
100M
–4
–2
TPC 7. On Response vs. Frequency
SOURCE VOLTAGE – V
25
Q
INJ
– pC
–10
0 0.5
–5
0
20
15
10
5
1 1.5 2 2.5 3 3.5 4 4.5 5
V
DD
= 5V
V
DD
= 3V
T
A
= 25C
TPC 8. Charge Injection vs. Source Voltage
APPLICATIONS
Figure 1 illustrates a photodetector circuit with programmable
gain. An AD820 is used as the output operational amplifier.
With the resistor values shown in the circuit, and using different
combinations of the switches, gain in the range of 2 to 16 can
be achieved.
5V
2.5V
R3
510k
C1
V
OUT
GND
D1
S1 D1
GAIN RANGE 2 TO 16
5V
AD820
S2
D2
S3 D3
S4
D4
(LSB) IN1
IN2
IN3
(MSB) IN4
R4
240k
R5
240k
R6
120k
R7
120k
R8
120k
R9
120k
R10
120k
R1
33k
R2
510k
2.5V
Figure 1. Photodetector Circuit with Programmable Gain
C