REV. A

–8–

AD8015

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 –4 dBm,

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

critical for sensitivity performance in this application. Note that

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

4

1

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

CLOCK

RECOVERY

LPF:

3dB@

0.7 x F

LPF:

3dB@

0.7 x F

QUANTIZER

R > 40

Ω

C1 >100pF

CLK

DATA

R

R

C1

10k

Ω

5

6

7

8

4

3

2

1

AD8015

50

Ω

+1

G = 3

G = 30

50

Ω

+1

– +

1.7V

0.01µF

7k

Figure 17. AC Coupled Photodiode Application for Improved Dynamic Range