MAX3658(2004) 데이터 시트보기 (PDF) - Maxim Integrated

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MAX3658
(Rev.:2004)

622Mbps, Low-Noise, High-Gain Transimpedance Preamplifier

Maxim Integrated 

622Mbps, Low-Noise, High-Gain

Transimpedance Preamplifier

P1

PAVG

P0

TIME

Figure 4. Optical Power Relations

where ρ is the photodiode responsivity in A/W and in is

the RMS noise current in amps. For example, with pho-

todiode responsivity of 0.9A/W, an extinction ratio of 10

and 45nA input-referred noise, the sensitivity of the

MAX3658 is:

SENSITIVITY

=

10log

12.7

2×

× 45nA

0.9A / W

×

×

11

9

×

1000 dBm

= − 34dBm

Actual results may vary depending on supply noise,

output filter, limiting amplifier sensitivity, and other fac-

tors (refer to application note HFAN-3.0.0: Accurately

Estimating Optical Receiver Sensitivity).

Maxim obtains -33dBm typ sensitivity combined with

the MAX3748.

Input Optical Overload

Overload is the largest input that the MAX3658 accepts

while meeting the pulse-width distortion specification.

Optical overload can be estimated in terms of average

power with the following equation:

OVERLOAD

=

10log

2mA

2× ρ

×

1000 dBm

For example, if photodiode responsivity is 1.0A/W, the

input overload is 0dBm.

Optical Linear Range

The MAX3658 has high gain, which limits the output for

large input signals. The MAX3658 operates in a linear

range for inputs not exceeding:

( ) LINEAR RANGE



= 10log

4µA ×

re + 1



× 1000dBm

( )  2 × ρ × re − 1



For example, with photodiode responsivity of 0.9A/W

and an extinction ratio of 10, the linear range is:

LINEARRANGE

=

10log

2

4µA ×

× 0.9

11

×9

×

1000 dBm

= − 25dBm

Interface Schematics

Equivalent Output Interface

The MAX3658 has a differential output structure with

75Ω termination (150Ω differential). Figure 5 is a simpli-

fied diagram of the output interface. Common test

equipment is designed with a 50Ω single-ended termi-

nation (100Ω differential). Figures 6a and 6b show alter-

nate interface schemes for the MAX3658.

VCC

ROUT

75Ω

VCC

ROUT

75Ω

OUT+

VCC

OUT-

Figure 5. Equivalent Output Interface

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