MAX3267 MAXIM [Maxim Integrated Products], MAX3267 Datasheet - Page 5

• Manufacturer Part Number: MAX3267
• Description: 1.25Gbps/2.5Gbps, 3V to 5.5V, Low-Noise Transimpedance Preamplifiers for LANs
• Manufacturer: MAXIM [Maxim Integrated Products]

The MAX3266 is a transimpedance amplifier designed
for 1.25Gbps fiber optic applications. Figure 2 is a func-
tional diagram of the MAX3266, which comprises a trans-
impedance amplifier, a voltage amplifier, an output
buffer, an output filter, and a DC cancellation circuit.
The MAX3267, a transimpedance amplifier designed
for 2.5Gbps fiber optic applications, shares similar
architecture with the MAX3266.
Figure 1. Typical Photodiode Capacitance vs. Bias Voltage
Figure 2. MAX3266 Functional Diagram
2.00
1.85
1.70
1.55
1.40
1.25
1.10
0.95
0.80
0.65
0.50
0
1.25Gbps/2.5Gbps, 3V to 5.5V, Low-Noise
FILTER
_______________________________________________________________________________________
Transimpedance Preamplifiers for LANs
IN
1
General Description
REVERSE BIAS (V)
V
2
CC
1.5k
3
4
R
F
TRANSIMPEDANCE
DISABLE
5
AMPLIFIER
LOWPASS FILTER
AMPLIFIER
VOLTAGE
The signal current at the input flows into the summing
node of a high-gain amplifier. Shunt feedback through
R
imately 2.2kΩ (1.0kΩ for MAX3267). Schottky diodes
clamp the output voltage for large input currents, as
shown in Figure 3.
The voltage amplifier converts single-ended signals to
differential signals and introduces a voltage gain.
The output buffer provides a reverse-terminated volt-
age output. The buffer is designed to drive a 100Ω dif-
ferential load between OUT+ and OUT-. The output
current is divided between internal, 50Ω load resistors
and the external load resistor. In the typical operating
circuit, this creates a voltage divider with gain of 1/2.
The MAX3266 can also be terminated with higher out-
put impedances, which increases gain and output volt-
age swing.
For optimum supply-noise rejection, the MAX3266
should be terminated with a differential load. If a single-
ended output is required, the unused output should be
similarly terminated. The MAX3266 will not drive a DC-
coupled, 50Ω grounded load.
F
converts this current to a voltage with gain of approx-
DC CANCELLATION
CIRCUIT
OUTPUT
BUFFER
Transimpedance Amplifier
50
50
MAX3266
OUTPUT
FILTER
Voltage Amplifier
Output Buffer
OUT+
OUT-
GND
V
CC
5