MAX3265EUE+ Maxim Integrated, MAX3265EUE+ Datasheet - Page 7

• Manufacturer Part Number: MAX3265EUE+
• Description: Special Purpose Amplifiers
• Manufacturer: Maxim Integrated
• Series: MAX3264, MAX3265, MAX3268, MAX3269, MAX3765, MAX3768r

Specifications of MAX3265EUE+

• Number Of Channels: Single
• Supply Current: 50 mA
• Maximum Power Dissipation: 2162 mW
• Maximum Operating Temperature: + 85 C
• Minimum Operating Temperature: - 40 C
• Supply Voltage - Max: 5.5 V
• Supply Voltage - Min: 3 V

The MAX3266 includes a one-pole lowpass filter that
limits the circuit bandwidth and improves noise perform-
ance.
The DC cancellation circuit uses low-frequency feed-
back to remove the DC component of the input signal
(Figure 4). This feature centers the input signal within
the transimpedance amplifier’s linear range, thereby
reducing pulse-width distortion on large input signals.
The DC cancellation circuit is internally compensated
and therefore does not require external capacitors. This
circuit minimizes pulse-width distortion for data
sequences that exhibit a 50% duty cycle. A duty cycle
significantly different from 50% will cause the MAX3266
to generate pulse-width distortion.
DC cancellation current is drawn from the input and
creates noise. For low-level signals with little or no DC
component, this is not a problem. Amplifier noise will
increase for signals with significant DC component (see
Typical Operating Characteristics).
Many of the MAX3266 specifications relate to the input
signal amplitude. When working with fiber optic
receivers, the input is usually expressed in terms of aver-
age optical power and extinction ratio. Figure 5 shows
Figure 3. MAX3266 Limited Output
AMPLITUDE
1.25Gbps/2.5Gbps, +3V to +5.5V, Low-Noise
Applications Information
_______________________________________________________________________________________
Transimpedance Preamplifiers for LANs
Optical Power Relations
DC Cancellation Circuit
TIME
OUTPUT (SMALL SIGNALS)
OUTPUT (LARGE SIGNALS)
Output Filter
relations that are helpful for converting optical power to
input signal when designing with the MAX3266.
Optical power relations are shown in Table 1; the defini-
tions are true if the average duty cycle of the input data
is 50%.
The input-referred RMS noise current (I
MAX3266 generally determines the receiver sensitivity.
To obtain a system bit error rate (BER) of 1E-12, the
SNR ratio must always exceed 14.1. The input sensitivi-
ty, expressed in average power, can be estimated as:
Where ρ is the photodiode responsivity in A/W.
The overload is the largest input that the MAX3266
accepts while meeting specifications. The optical over-
load can be estimated in terms of average power with
the following equation:
Figure 4. DC Cancellation Effect on Input
Sensitivity
AMPLITUDE
Overload
=
10
Optical Sensitivity Calculation
INPUT (AFTER DC CANCELLATION)
log
=
10




14 1
log
INPUT FROM PHOTODIODE
.
Input Optical Overload
2



ρ
I
1
(
N
r
mA
2
e
ρ
(
r
−
e
1000
1
+
)
1



)
1000
dBm
TIME




N
) of the
dBm
7