sensitivity. To obtain a system bit error rate (BER) of 1E-

12, the signal-to-noise ratio must always exceed 14.1.

The input sensitivity, expressed in average power, can

be estimated as:

where

RMS current in Amps.

Input Optical Overload

The overload is the largest input that the MAX3275/

MAX3277 accept while meeting specifications. The

optical overload can be estimated in terms of average

power with the following equation:

Optical Linear Range

The MAX3275/MAX3277 have high gain, which limits

MAX3275/MAX3277 operate in a linear range (10% lin-

earity) for inputs not exceeding:

Layout Considerations

Noise performance and bandwidth will be adversely

affected by capacitance at the IN pad. Minimize

capacitance on this pad and select a low-capacitance

photodiode. Assembling the MAX3275/MAX3277 in die

form using chip and wire technology provides the best

possible performance. Figure 5 shows a suggested lay-

out for a TO header for the MAX3275/MAX3277.

Special care should be taken to ensure that ESD at IN

does not exceed 500V.

Photodiode Filter

Supply voltage noise at the cathode of the photodiode

∆V/∆t, which reduces the

tance). The filter resistor of the MAX3275/MAX3277,

combined with an external capacitor, can be used to

reduce this noise (see the Typical Application Circuit).

Current generated by supply noise voltage is divided

to supply noise is (assuming the filter capacitor is much

larger than the photodiode capacitance):

If the amount of tolerable noise is known, the filter

capacitor can be easily selected:

be 350nA:

Ω)(350nA) = 400pF

Wire Bonding

For high-current density and reliable operation, the

MAX3275/MAX3277 use gold metalization. Connections

to the die should be made with gold wire only, using

ball-bonding techniques. Wedge bonding is not recom-

mended. Die thickness is typically 15 mils (0.4mm).

Linear Range=10 log

50E - 6 r +1

1000

2(r -1)

e

e













ρ

dBm

Overload=10 log

2E - 3 r +1

1000

2(r -1)

e

e













ρ

dBm

Sensitivity =10 log

14.1I (r +1) 1000

2(r -1)

Ne

e

×









ρ

dBm

Low-Noise, Fibre Channel Transimpedance

Amplifiers

_______________________________________________________________________________________

7

CASE IS GROUND

OUTPUT POLARITIES

REVERSED FOR MAX3277

PHOTODIODE

MAX3275

OUT-

CAP

OUT+

Figure 5. Suggested Layout for TO-46 Header

Pad Coordinates

PAD#

COORDINATES (µm)

1

16, 39

2

16, 372

3

16, 806

4

358, 806

5

358, 341

6

358, 36

7

362, -116

8

250, -116

9

138, -116