The MAX3665 low-power transimpedance preamplifier
for 622Mbps SDH/SONET applications consumes only
70mW at VCC = 3.3V. Operating from a single +3.3V or
+5.0V supply, it converts a small photodiode current to a
measurable differential voltage. A DC cancellation circuit
provides a true differential output swing over a wide
range of input current levels, thus reducing pulse-width
distortion. The differential outputs are back-terminated
with 50Ω per side.
The overall transimpedance gain is nominally 8kΩ. For
input signal levels beyond approximately 50µAp-p, the
amplifier will limit the output swing to 250mV. The
MAX3665's low 55nA input noise provides a typical
sensitivity of -33.2dBm in 1300nm, 622Mbps receivers.
The MAX3665 is designed to be used in conjunction
with the MAX3676 clock recovery and data retiming IC
with limiting amplifier. Together they form a complete
3.3V or 5.0V 622Mbps SDH/SONET receiver.
In die form, the MAX3665 is designed to fit on a header
with a PIN diode. It includes a filter connection that provides
positive bias for the photodiode through a 1.5kΩ resistor to VCC. The device is available in an 8-pin
µMAX® package.
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