The GaAs MESFET as a pulse regenerator, amplifier, and laser modulator in the Gbit/s range

Using GaAs MESFET´s under switching conditions, the regeneration and amplification of fast pulses and the modulation of semiconductor lasers in the Gbit/s speed range is performed. Sharpening factors of 3 at output pulse rise times of nearly 50 ps and voltage amplification factors of 2 at 50 Ω are attained for output pulses up to 100 mA. The regeneration is caused by the clamping at the input port of the MESFET and by the nonlinear transconductance characteristic. In the pulse modulation mode, the laser diode is directly controlled by the MESFET. The switching behavior of the driver stage is calculated using the equivalent circuit of the laser diode and of the MESFET. This evaluation reveals that the maximum pulse rate is limited by the laser diode.