  The Quad transimpedance and limiting amplifier (QTIA) is a 4-channel array
optical receiver ASIC, developed using a 65 nm CMOS process. It is configurable
between the bit rate of 2.56 Gbps and 10 Gbps per channel. QTIA offers careful
matching to both GaAs and InGaAs photodiodes. At this R&D stage, each channel
has a different biasing scheme to the photodiode for optimal coupling. A charge
pump is implemented in one channel to provide a higher reverse bias voltage,
which is especially important to mitigate radiation effects on the photodiodes.
The circuit functions of QTIA successfully passed the lab tests with GaAs
photodiodes.
