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Philips Semiconductors
SA5211
Transimpedance amplifier (180 MHz)
Product specification Rev. 03 — 07 October 1998 16 of 28
9397 750 07427
© Philips Electronics N.V. 2001. All rights reserved.
where e = electron charge = 1.6 × 10
-19
Coulombs
Responsivity R = Amp/watt
Assuming a data rate of 400 Mbaud (Bandwidth, B = 200 MHz), the noise parameter
Z
n
may be calculated as:
1
(8)
where Z is the ratio of
RMS
noise output to the peak response to a single hole-electron
pair. Assuming 100% photodetector quantum efficiency, half mark/half space digital
transmission, 850nm lightwave and using Gaussian approximation, the minimum
required optical power to achieve 10
-9
BER is:
(9)
where h is Planck’s Constant, c is the speed of light, λ is the wavelength. The
minimum input current to the SA5211, at this input power is:
(10)
Choosing the maximum peak overload current of I
avMAX
=60µA, the maximum mean
optical power is:
(11)
Thus the optical dynamic range, D
O
is:
(12)
1. S.D. Personick,
Optical Fiber Transmission Systems,
Plenum Press, NY, 1981, Chapter 3.
I∴η
P
hc
-----
λ
-----
× e Amps (Coulombs/sec.)×=
η e×
hc
-------------
λ
-------------
I PR×=
Z
I
EQ
qB
--------
41 10
9–
×
1.6 10
19–
×()200 10
6
×()
------------------------------------------------------------
1281== =
P
avMIN
12
hc
λ
-----
BZ 12 2.3× 10
19–
×==
200 10
6
× 1281()719 nW 31.5 dBm– 1139 nW 29.4 dBm–== = =
I
avMIN
qP
avMIN
λ
hc
-----
1
Joule
------------
Joule
sec
------------
× q× = l =
707 10
9–
× 1.6× 10
19–
×
2.3 10
19–
×
-----------------------------------------------------------
500 nA==
P
avMAX
hcl
avMAX
λq
----------------------
2.3 10
19–
×
1.6 10
19–
×
--------------------------
60 10 µA× 86 µW or 10.6 dBm (optical)–===
D
O
P
avMAX
P
avMIN
– 4.6– 29.4–()24.8 dB=–==
D
O
P
avMAX
P
avMIN
– 31.5– 10.6–()–==