Philips SA5211 - page 16

Philips Semiconductors SA5211

Transimpedance ampliﬁer (180 MHz)

Product speciﬁcation Rev. 03 — 07 October 1998 16 of 28

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

Zn 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 IavMAX =60µA, the maximum mean

optical power is:

(11)

Thus the optical dynamic range, DO is:

(12)

1. S.D. Personick,

Optical Fiber Transmission Systems,

Plenum Press, NY, 1981, Chapter 3.

I∴η

-----

×e Amps (Coulombs/sec.)×=

ηe×

-------------

IPR×=

ZIEQ

--------41 10 9–

1.6 10 19–

×()200 106

×()

------------------------------------------------------------ 1281== =

PavMIN 12hc

----- BZ 12 2.3×10 19–

×==

200 106

×1281()719 nW 31.5 dBm– 1139 nW 29.4 dBm–== = =

IavMIN qPavMIN λ

----- 1

Joule

------------ Joule

sec

------------

×q×= l = 707 10 9–

×1.6×10 19–

2.3 10 19–

-----------------------------------------------------------500 nA==

PavMAX

hclavMAX

λq

----------------------2.3 10 19–

1.6 10 19–

-------------------------- 60 10 µA×86 µW or 10.6 dBm (optical)–===

DOPavMAX PavMIN

–4.6–29.4–()24.8 dB=–==

DOPavMAX PavMIN

–31.5–10.6–()–==