M02024-BRF-001-A_15 Datasheet, PDF (1/2 Pages) M/A-COM Technology Solutions, Inc. – 2.5 Gbps High Sensitivity Transimpedance Amplifier with AGC

®
2.5 Gbps High Sensitivity Transimpedance Amplifier with AGC
M02024
Low-power, high-sensitivity 2.5 Gbps TIA for
GPON and OC48 applications
The M02024 transimpedance amplifier (TIA) with
automatic gain control (AGC) is fabricated in
sub-micron CMOS for high performance. The
device targets a sensitivity of -29dBm, enabling
the use of low cost PIN diodes to meet the GPON
Class B+ standard.
In order to satisfy such high sensitivity and good
optical overload requirements, automatic gain
control (AGC) is implemented in the M02024. The
AGC monitors the output amplitude and auto-
matically reduces the TIA gain when the
photodiode current exceeds the AGC threshold,
maintaining the output at a constant level. With
an input overload capability greater than +6 dBm,
the AGC allows more than 35 dB of dynamic
range, providing a low-cost solution for longer-
reach 2.5 Gbps GPON/ATM/SONET systems that
formerly required an APD. For even greater sen-
sitivity, the M02024 may be used with an APD.
The TIA consists of a high gain single-ended
CMOS amplifier with a feedback resistor. The
feedback creates a virtual low impedance at the
input, and nearly all of the input current passes
through the feedback resistor, defining the volt-
age at the output. Advanced CMOS design
techniques are employed to maintain the stability
of this stage across all input conditions. An on-
chiplow dropout linear regulator has been
incorporated into the design to give excellent
noise rejection up to several MHz.
> Key Features
> -29 dBm Sensitivity
> Photodiode current monitor
> Data rates to 2.5 Gbps
> Integrated filter, eliminates
need for a capacitor on the
photodiode cathode
> AGC provides dynamic
range of 35 dB
> Internal or external bias for
photodiode
> Single +3.3V supply
> Same pad layout and die
size as
M02011/13/14/15/16
> +6 dBm Input overload
Higher frequency noise is removed by the inte-
grated filter, eliminating the need for an external
capacitor on the photodiode cathode.
The circuit is intended to be configured for use
with PIN photodiodes in the “grounded cathode”
configuration with the anode connected to the
input of the TIA and the cathode connected to
the PINK terminal. The PINK terminal provides
~2V reverse DC bias to reduce the photodiode
capacitance. Operation with an external photodi-
ode bias supply is also possible, as required by
avalanche photodiodes.
A replica of the average photodiode current is
available at the MON pad for photo-alignment,
monitoring average power and 'Loss of Signal'
detection.
For optimum system performance, the M02024
die should be mounted with the photodetector
inside a lensed TO-Can or other optical sub-
assembly.
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