Optical Linear Range

The MAX3271 has high gain, which limits the output

when the input signal exceeds 40µAp-p. The MAX3271

operates in a linear range for inputs not exceeding:

Layout Considerations

Noise performance and bandwidth will be adversely

affected by capacitance at the IN pin. Minimize capaci-

tance on this pin and select a low-capacitance photodi-

ode. Assembling the MAX3271 in die form using chip

and wire technology provides the best possible perform-

ance. Figure 5 shows a suggested layout for a TO

header.

Photodiode Filter

Supply voltage noise at the cathode of the photodiode

∆V/∆t, which reduces the

tance.) The filter resistor of the MAX3271, combined

with an external capacitor, can be used to reduce this

noise (see the Typical Application Circuit). Current gen-

erated by supply noise voltage is divided between

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:

For example, with maximum noise voltage = 100mVp-p,

be 250nA (1/2 of the MAX3271’s input noise):

Ω)(250nA) = 450pF

Wire Bonding

For high-current density and reliable operation, the

MAX3271 uses 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 15mils (0.375mm).

Linear Range

Ar

r

dBm

e

e

=

+

()

()













−

10

40

1

21

1000

log

µ

ρ

+3.3V, 2.5Gbps Low-Power

Transimpedance Amplifier

_______________________________________________________________________________________

7

PARAMETER

SYMBOL

RELATION

Average Power

Extinction Ratio

Optical Power

of a 1

P1

Optical Power

of a 0

P0

Signal Amplitude

Table 1. Optical Power Relations

CASE IS GROUND

TOP VIEW OF TO-56 HEADER

PHOTODIODE

MAX3271

OUT+

OUT-

Figure 5. Suggested Layout for TO-56 Header