ADG711/ADG712/ADG713
APPLICATIONS
Figure 9 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.
C1
R1
33k
+5V
AD820
D1
+2.5V
R2
510k
+5V
R4
240k
R6
120k
R8
120k
R9
120k
+2.5V
R10
120k
GAIN RANGE 2 TO 16
R5
240k
R7
120k
R3
510k
V
OUT
S1
(LSB) IN1
S2
IN2
S3
IN3
S4
(MSB) IN4
GND
D1
D2
D3
D4
Figure 9. Photodetector Circuit with Programmable Gain
Test Circuits
I
DS
V1
I
S
(OFF)
S
V
S
R
ON
= V1/I
DS
D
V
S
A
S
D
I
D
(OFF)
A
V
D
S
V
S
D
I
D
(ON)
A
V
D
Test Circuit 1. On Resistance
V
DD
0.1 F
Test Circuit 2. Off Leakage
Test Circuit 3. On Leakage
V
IN
ADG711
V
DD
50%
50%
S
V
S
IN
GND
D
R
L
300
C
L
35pF
V
IN
ADG712
V
OUT
50%
V
S
50%
90%
V
OUT
90%
t
ON
t
OFF
Test Circuit 4. Switching Times
V
DD
0.1 F
V
IN
0V
50%
50%
V
DD
V
S1
V
S2
IN1, IN2
S1
S2
D1
D2
R
L2
300
C
L2
35pF
V
OUT2
R
L1
300
C
L1
35pF
V
OUT1
V
OUT1
0V
90%
90%
V
IN
ADG713
GND
V
OUT2
0V
90%
90%
t
D
t
D
REV. 0
Test Circuit 5. Break-Before-Make Time Delay, t
D
–7–
AD [ ANALOG DEVICES ]
