Datasheet

REV. A
–8–
AD8015
PRINTED IN U.S.A.
C1973–6–1/96
AC COUPLED PHOTODIODE APPLICATION FOR
IMPROVED DYNAMIC RANGE
AC coupling the photodiode current input to the AD8015 (Fig-
ure 17) extends fiber optic receiver overload by 3 dB while sacri-
ficing only 1 dB of sensitivity (increasing receiver dynamic range
by 2 dB). This application results in typical overload of –4dBm,
and typical sensitivity of –35 dBm. AC coupling the input also
results in improved pulse width modulation performance.
Careful attention to minimize parasitic capacitance at the
AD8015 input (from the photodetector input), R
AC
and C
AC
are
critical for sensitivity performance in this application. Note that
C
AC
of 0.01 µF was chosen for a low frequency cutoff equal to
2.2 kHz.
OUTLINE DIMENSIONS
Dimensions shown in inches and (mm).
8-Lead Small Outline IC Package (SO-8)
0.1968 (5.00)
0.1890 (4.80)
8
5
41
PIN 1
0.1574 (4.00)
0.1497 (3.80)
0.0688 (1.75)
0.0532 (1.35)
SEATING
PLANE
0.0098 (0.25)
0.0040 (0.10)
0.020 (0.51)
0.013 (0.33)
0.0500
(1.27)
BSC
0.0098 (0.25)
0.0075 (0.19)
0.0500 (1.27)
0.0160 (0.41)
8°
0°
0.0196 (0.50)
0.0099 (0.25)
x 45°
0.2440 (6.20)
0.2284 (5.80)
V1
+V
S
CLOCK
RECOVERY
LPF:
3dB@
0.7 x F
LPF:
3dB@
0.7 x F
QUANTIZER
R > 40Ω
C1 >100pF
4.5V < V
S
< 11V
CLK
DATA
R
R
C1
10kΩ
5
6
7
8
4
3
2
1
AD8015
50Ω
+1
G = 3
G = 30
50Ω
+1
– + +V
S
1.7V
+V
S
C
AC
0.01µF
R
AC
7k
Figure 17. AC Coupled Photodiode Application for Improved Dynamic Range