Design of low noise wide dynamic range GaAs optical preamps

FET devices have a fundamental advantage over BJT transistors in low noise applications because of their inherent high input impedance. Another advantage comes from the fact that FETs are majority carrier devices and can be easily used in automatic gain control applications. Using these advantages, two different preamp designs are presented. The first obtains a 2 GHz bandwidth using a 5 K Ω feedback resistors. The second achieves a 200 MHz bandwidth and -38 dB sensitivity. Use of an on-chip AGC results in an overload of O dBm (1 mA) of input signal