02013-BRF-001-A Datasheet, PDF (1/2 Pages) M/A-COM Technology Solutions, Inc. – 3.2 Gbps Transimpedance Amplifier with AGC

3.2 Gbps Transimpedance Amplifier with AGC
M02013
Low-power, high-sensitivity 3.2 Gbps transimped-
ance amplifier fabricated in a sub-micro CMOS
process
The M02013 is a transimpedance amplifier (TIA) with auto-
matic gain control (AGC) manufactured in a sub-micron,
CMOS process. The AGC allows more than 25 dB of dynamic
range, providing a low-cost solution for longer-reach 3.2
Gbps ATM/SONET systems.
For optimum system performance, the M02013 die should be
mounted with a silicon or InGaAs PIN photodetector inside a
lensed TO-Can or other optical sub-assembly.
The M02013 reverse biases the PIN by approximately 1.8
volts to optimise performance. A replica of the average
photodiode current is available at the MON pad for align-
ment and 'LOSS of SIGNAL' monitoring.
Transimpedance Amplifier (TIA)
The TIA consists of a high gain single-ended CMOS amplifier
with a feedback resistor. The feedback creates a virtual
earth low impedance at the input, and virtually all of the
input current passes through the feedback resistor,
defining the voltage at the output. Advanced CMOS design
techniques are employed to maintain the stability of this
stage across all input conditions. Single-ended amplifiers
have inherently poor power supply noise rejection. For this
reason, an on-chip low dropout linear regulator has been
incorporated into the design to give excellent noise rejection
> KEY FEATURES
> Typical -23 dBm sensitivity,
+3 dBm saturation at 3.2
Gbps
> Typical differential transim-
pedance: 10kW
> Differential output
> Operates with +3.3V supply
> Monitor output
> AGC provides dynamic range
of more than 25 dB
up to several MHz. Higher frequency power supply noise is
removed by the external 470 pF decoupling capacitor
connected to PINK.
The circuit is designed for PIN photodiodes in the “grounded
cathode” configuration with the anode connected to the
input of the TIA and the cathode connected to AC ground,
such as the provided PINK terminal. Reverse DC bias is
applied to reduce the photodiode capacitance. Avalanche
photodiodes can be connected externally to a higher
voltage.
Automatic Gain Control (AGC)
The M02013 has been designed to operate over the input
range of +3 dBm to –23 dBm @ 3.2 Gbps and –24 dBm @ 2.5
Gbps. This represents a ratio of 1:300, whereas the accept-
able dynamic range of the output is only 1:30 which implies a
compression of 10:1 in the transimpedance. The design uses
a MOS transistor operating in the triode region as a
“voltage controlled resistor” to achieve the transimpedance
variation.
>